Peter A Troch

Interests

Research

Troch’s research focuses on catchment hydrology, including in-situ data collection, field and laboratory experimentation, remote sensing, physically-based modeling and data assimilation. His research aims to address the following questions: i) what controls hydrological partitioning across scales, ii) what defines hydrological similarity across catchments; iii) how have catchments evolved in relation to climate and geology, and how will hydrologic response change in a changing environment. Applications of his research include improving mountain block recharge estimates in semi-arid environments, the role of ecosystems in catchment water balance, catchment classification in ungauged basins, predicting water availability at seasonal, annual and decadal time scales, and improving the physical basis of operational flash flood forecasting models.

Teaching

My approach to teaching the core course HWR519 is to provide the students with the physical and mathematical background to understand processes at and below the land surface that control water and energy partitioning. Unlike many other similar courses taught in other departments (Civil and Environmental Engineering at the UA and other universities across the country), this course takes the scientific approach to surface hydrology rather than an engineering approach. Therefore it is a challenging course to teach as well as for the students to take. I provide the students with several homework assignments to give them the opportunity to deeply understand the material covered during lectures. I also have designed a class project that allow the students to explore real world catchment data (precipitation, temperature, stream flow) in order to understand how the different processes discussed in class work together to generate hydrologic response (stream flow, evapotranspiration) in different climates and in different geophysical environments (geology, topography, geomorphology). This prepares them to become watershed hydrologists and is the perfect introduction to my follow-up courses. HWR630 is designed to raise the scientific level of the students such that they know the literature in different elements of catchment hydrology: geomorphological controls on hydrology, rainfall-runoff processes and modeling approaches, the role of vegetation in the hydrological cycle, water residence time in catchments and its controls, transport of nutrients and solutes at catchment scales, and remote sensing techniques to monitor hydrological stores and fluxes. The class project involves the use of a catchment model to answer specific science questions related to the student’s research interests. The final course, HWR696F is a seminar class that focuses on an active research field in catchment hydrology. The ambition of the class is to write a review paper such that the students get familiar with the art of scientific writing, based on thorough review of recent literature.My goals in advising students (at both the MSc and PhD level) are to make intellectual leaders out of them. Graduates from our department should have the intellectual power to lead in whatever situation they end up with. Leadership combines intelligence, self-confidence, compassion and empathy, and I try to teach them these principles through example.

Courses

Scholarly Contributions

Books

• Sengupta, A., Pangle, L. A., Volkmann, T., Dontsova, K., Troch, P. A., Meira-Neto, A. A., Neilson, J. W., Hunt, E. A., Chorover, J., Zeng, X., Haren, J., Barron-Gafford, G. A., Bugaj, A., Abramson, N., Sibayan, M., & Huxman, T. E. (2017). Advancing Understanding of Hydrological and Biogeochemical Interactions in Evolving Landscapes through Controlled Experimentation at the Landscape Evolution Observatory.
• Guardiola-Claramonte, M. .., Fox, J. M., Giambelluca, T. W., & Troch, P. A. (2010). Changing land use in the Golden Triangle: Where the rubber meets the road.
• Troch, P. A., Smith, J. A., Wood, E. F., & De, T. F. (1993). Empirical and model based analysis of extreme flood events in a humid region.
• Troch, P. A., De, T. F., & Van Erdeghem, D. (1991). Operational flood forecasting on the River Meuse using on-line identification.
• Troch, P. A., De, T. F., & Van Hyfte, J. (1991). Modelling the time-dependent nature of the rainfall-runoff relationship using on-line identification.
• De, T. F., Heynderickx, J., Troch, P. A., & Van Erdeghem, D. (1990). On the usefulness of weather radar data in real-time hydrological forecasting in Belgium.

Chapters

• Moore, G. W., McGuire, K., Troch, P. A., & Barron-Gafford, G. A. (2014). Ecohydrology and the Critical Zone: Processes and Patterns across Scales. In Principles and Dynamics of the Critical Zone(p. 27). Giardino and Houser (Eds.): Elsevier.
• Volkmann, T. H., Sengupta, A., Pangle, L., Dontsova, K. M., Troch, P. A., Meira, A., Neilson, J., Hunt, E., Chorover, J. D., Zeng, X., Van Haren, J. L., Barron-Gafford, G. A., Bugaj, A., Abramson, N., Sibayan, M., & Huxman, T. E. (2018). Controlled experiments of hillslope coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward prediction of coupled hydrological, biogeochemical, and ecological change. In Hydrology of Artificial and Controlled Experiments. Rijeka, Croatia: InTech.
• Sengupta, A., Pangle, L., Volkmann, T., Dontsova, K. M., Troch, P. A., Meira, A. A., Neilson, J. W., Hunt, E., Chorover, J. D., Zeng, X., Van Haren, J. L., Barron-Gafford, G. A., Bugaj, A., Abramson, N., Sibayan, M., & Huxman, T. E. (2017). Advancing understanding of hydrological and biogeochemical interactions in evolving landscapes through controlled experimentation and monitoring at the Landscape Evolution Observatory. In Terrestrial Ecosystem Research Infrastructures: Challenges, New Developments and Perspectives(pp 83-118). CRC Press.
• Volkmann, T. H., Sengupta, A., Pangle, L. A., Dontsova, K. M., Barron-Gafford, G. A., Harman, C. J., Niu, G., Meredith, L., Abramson, N., Alves Meira Neto, A., Wang, Y., Adams, J. R., Breshears, D. D., Bugaj, A., Chorover, J. D., Cueva, A., DeLong, S. B., Durcik, M., Ferre, P. A., , Huxman, T. E., et al. (2017). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments. Rijeka, Croatia: IN TECH d.o.o.
• Sengupta, A., Pangle, L. A., Volkmann, T., Dontsova, K. M., Troch, P. A., Meira, A. A., Neilson, J. W., Hunt, E. A., Chorover, J. D., Zeng, X., van Haren, J., Barron-Gafford, G. A., Bugai, A., Abramson, N., Sibayan, M., & Huxman, T. E. (2016). Advancing understanding of hydrological and biogeochemical interactions in evolving landscapes through controlled experimentation and monitoring at the Landscape Evolution Observatory. In Terrestrial Ecosysem Research Infrastructrures: Challenges, New Developments and Perspectives(pp 83-118). Taylor and Francis Group, London UK.

Journals/Publications

• Chorover, J. D., Troch, P. A., Chen, L., Hitzerlberger, M., Dontsova, K. M., Niu, G., Wang, Y., Guo, B., & Cao, Z. (2021). Reactive transport modeling of basalt weathering and early soil formation within a highly-controlled, sloping lysimeter.. Geochemistry, Geophysics, Geosystems.
• Destouni, G., Bierkens, M. F., Castelletti, A., Fatichi, S., Hall, J., Islam, S., Jha, M. K., Kollet, S., Moradkhani, H., Sanchez‐Vila, X., Singha, K., Stahl, K., Troch, P. A., & Wohl, E. (2023).

  Gratitude for the Time and Expertise of Our Valued 2022 Reviewers

  . Water Resources Research, 59(6). doi:10.1029/2023wr035329
• Dontsova, K. M., Juarez, S., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2017). Effect of elevated CO2 and temperature on weathering of basalt without and in the presence of higher plants. Geobiology.
• Dontsova, K. M., Juarez, S., Villasenor, E., Le Galliard, J., Chollet, S., Llavata, M., Massol, F., Barré, P., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2017). Nutrient uptake by plants grown in basaltic soil impacted by climate change. Geobiology.
• Kim, M., Bauser, H. H., Beven, K., & Troch, P. A. (2023).

  Time‐Variability of Flow Recession Dynamics: Application of Machine Learning and Learning From the Machine

  . Water Resources Research, 59(5). doi:10.1029/2022wr032690
• Van Haren, J. L., Dontsova, K. M., Juarez, S., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Troch, P. A., Barron-Gafford, G. A., & Ferriere, R. H. (2017). Rapid CO2 drawdown during basalt weathering as affected by climate change. Geochimica et Cosmochimica Acta.
• Bauser, H. H., Kim, M., Ng, W., Bugaj, A., & Troch, P. A. (2022). Richards Equation at the Hillslope Scale: Can We Resolve the Heterogeneity of Soil Hydraulic Material Properties?. Water Resources Research, 58(12).
• Destouni, G., Bierkens, M., Hall, J., Islam, S., Jha, M. K., Kollet, S., Luce, C. H., Mackay, D. S., Moradkhani, H., Sanchez-Vila, X. .., Singha, K., Stahl, K., Troch, P. A., & Wohl, E. (2022). Thank You to Our 2021 Reviewers. Water Resources Research, 58(4).
• Kim, M., Volkmann, T., Wang, Y., Meira, N. A., Matos, K., Harman, C. J., & Troch, P. A. (2022). Direct Observation of Hillslope Scale StorAge Selection Functions in Experimental Hydrologic Systems: Geomorphologic Structure and Preferential Discharge of Old Water. Water Resources Research, 58(3).
• Meira, N. A., Kim, M., & Troch, P. A. (2022). Physical Interpretation of Time-Varying StorAge Selection Functions in a Bench-Scale Hillslope Experiment via Geophysical Imaging of Ages of Water. Water Resources Research, 58(4).
• Wang, C., Liu, G., McNew, C. P., Volkmann, T., Pangle, L., Troch, P. A., Lyon, S. W., Kim, M., Huo, Z., & Dahlke, H. E. (2022). Simulation of experimental synthetic DNA tracer transport through the vadose zone. Water Research, 223.
• Yoshida, T., Hanasaki, N., Nishina, K., Boulange, J., Okada, M., & Troch, P. A. (2022). Inference of Parameters for a Global Hydrological Model: Identifiability and Predictive Uncertainties of Climate-Based Parameters. Water Resources Research, 58(2).
• Almagro, A., Oliveira, P., Meira, N., Roy, T., & Troch, P. (2021). CABra: a novel large-sample dataset for Brazilian catchments. Hydrology and Earth System Sciences, 25(6), 3105--3135.
• Cueva, A., Meredith, L., & Troch, P. A. (2019). Reconciling negative soil co2 fluxes: Insights from a large-scale experimental hillslope. Soil Systems, 3, 1-20.
• Evaristo, J., Troch, P. A., & McDonnell, J. J. (2019). Characterizing the Fluxes and Age Distribution of Soil Water, Plant Water, and Deep Percolation in a Model Tropical Ecosystem. Water Resources Research, 55, 3307-3327.
• Kim, M., Volkmann, T., Bugaj, A., Wang, Y., Meira, N. A., Matos, K., Harman, C. J., & Troch, P. A. (2021). Uncovering the hillslope scale flow and transport dynamics in an experimental hydrologic system. Hydrological Processes, 35(8).
• Knighton, J., & Troch, P. A. (2019). Seasonal and Topographic Variations in Ecohydrological Separation Within a Small, Temperate, Snow-Influenced Catchment. Water Resources Research, 55, 6417-6435.
• Meredith, L., Troch, P. A., Chorover, J. D., Maier, R. M., Neilson, J. W., Barberan, A., Meira-Neto, A. A., Matos, K. A., Volk, M. J., Bugaj, A. S., Abramson, N., Dontsova, K. M., Stegen, J. C., Danczak, R. E., Volkmann, T. H., & Sengupta, A. (2021). Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System.. Frontiers in Microbiology, 12(3414).
• Sengupta, A., & Troch, P. A. (2019). Assessing Microbial Community Patterns During Incipient Soil Formation From Basalt. Journal of Geophysical Research: Biogeosciences, 124, 941-958.
• Sengupta, A., Volkmann, T. H., Danczak, R. E., Stegen, J. C., Dontsova, K., Abramson, N., Bugaj, A. S., Volk, M. J., Matos, K. A., Meira-Neto, A. A., & others, . (2021). Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System.. Frontiers in microbiology, 12, 754698--754698.
• Sengupta, A., Volkmann, T., Danczak, R. E., Stegen, J. C., Dontsova, K., Abramson, N., Bugaj, A. S., Volk, M. J., Matos, K. A., Meira-Neto, A. A., Barber??n, A., Neilson, J. W., Maier, R. M., Chorover, J., Troch, P. A., & Meredith, L. K. (2021). Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System. Frontiers in Microbiology, 12.
• Troch, P. A., Wang, C., & Lyon, S. (2019). Particle tracer transport in a sloping soil lysimeter under periodic, steady state conditions. Journal of Hydrology, 569, 61-76.
• Arevalo, J., Zeng, X., Durcik, M., Sibayan, M., Pangle, L., Abramson, N., Bugaj, A., Ng, W., Kim, M., Barron-Gafford, G. .., Haren, J., Niu, G., Adams, J., Ruiz, J., & Troch, P. A. (2020). Highly sampled measurements in a controlled atmosphere at the Biosphere 2 Landscape Evolution Observatory. Scientific Data, 7(1).
• Arevalo, J., Zeng, X., Durcik, M., Sibayan, M., Pangle, L., Abramson, N., Bugaj, A., Ng, W., Kim, M., Barron-Gafford, G., & others, . (2020). Highly sampled measurements in a controlled atmosphere at the Biosphere 2 Landscape Evolution Observatory. Scientific Data, 7(1), 1--12.
• Bauser, H. H., Riedel, L., Berg, D., Troch, P. A., & Roth, K. (2020). Challenges with effective representations of heterogeneity in soil hydrology based on local water content measurements. Vadose Zone Journal, 19(1), e20040.
• Bauser, H. H., Riedel, L., Berg, D., Troch, P. A., & Roth, K. (2020). Challenges with effective representations of heterogeneity in soil hydrology based on local water content measurements. Vadose Zone Journal, 19(1).
• Dusza, Y., Sanchez-Ca??ete, E., Galliard, J., Ferri??re, R., Chollet, S., Massol, F., Hansart, A., Juarez, S., Dontsova, K., Haren, J. V., Troch, P., Pavao-Zuckerman, M. A., Hamerlynck, E., & Barron-Gafford, G. A. (2020). Author Correction: Biotic soil-plant interaction processes explain most of hysteretic soil CO2 efflux response to temperature in cross-factorial mesocosm experiment (Scientific Reports, (2020), 10, 1, (905), 10.1038/s41598-019-55390-6). Scientific Reports, 10(1).
• Heidb\"uchel, I., Yang, J., Musolff, A., Troch, P., Ferr\'e, T., & Fleckenstein, J. H. (2020). On the shape of forward transit time distributions in low-order catchments. Hydrology and Earth System Sciences, 24(6), 2895--2920.
• Kim, M., & Troch, P. A. (2020). Transit Time Distributions Estimation Exploiting Flow-Weighted Time: Theory and Proof-of-Concept. Water Resources Research, 56(12), e2020WR027186.
• Kim, M., & Troch, P. A. (2020). Transit Time Distributions Estimation Exploiting Flow-Weighted Time: Theory and Proof-of-Concept. Water Resources Research, 56(12).
• Kim, M., Volkmann, T. H., Wang, Y., Meira, N., Matos, K., Harman, C. J., & Troch, P. A. (2020). Direct observation of hillslope scale StorAge Selection functions in experimental hydrologic systems: Geomorphologic structure and preferential discharge of old water. Water Resources Research, e2020WR028959.
• Meira, N. A., Niu, G., Roy, T., Tyler, S., & Troch, P. A. (2020). Interactions between snow cover and evaporation lead to higher sensitivity of streamflow to temperature. Communications Earth and Environment, 1(1).
• Meira, N. A., Roy, T., Oliveira, P., & Troch, P. A. (2020). An Aridity Index-Based Formulation of Streamflow Components. Water Resources Research, 56(9).
• Meira, N., Roy, T., Oliveira, P., & Troch, P. A. (2020). An aridity index-based formulation of streamflow components. Water Resources Research, 56(9), e2020WR027123.
• Neto, A., Niu, G., Roy, T., Tyler, S., & Troch, P. A. (2020). Interactions between snow cover and evaporation lead to higher sensitivity of streamflow to temperature. Communications Earth \& Environment, 1(1), 1--7.
• Sengupta, A., Kushwaha, P., Jim, A., Troch, P. A., & Maier, R. (2020). New Soil, Old Plants, and Ubiquitous Microbes: Evaluating the Potential of Incipient Basaltic Soil to Support Native Plant Growth and Influence Belowground Soil Microbial Community Composition. Sustainability, 12(10), 4209.
• Sengupta, A., Kushwaha, P., Jim, A., Troch, P. A., & Maier, R. (2020). New soil, old plants, and ubiquitous microbes: Evaluating the potential of incipient basaltic soil to support native plant growth and influence belowground soil microbial community composition. Sustainability (Switzerland), 12(10).
• Barron-Gafford, G. A., Hamerlynck, E., Pavao-Zuckerman, M. A., Troch, P. A., Van Haren, J. L., Dontsova, K. M., Juarez, S., Hansart, A., Massol, F., Chollet, S., Ferriere, R. H., Le Galliard, J., Sanchez-Canete, E. P., & Dusza, Y. (2019). Biotic soil-plant interaction processes explain most of hysteric soil CO2 efflux response to temperature in cross-factorial mesocosm experiment.. Scientific Reports.
• Cueva, A., Volkmann, T. H., Haren, J., Troch, P. A., & Meredith, L. K. (2019). Reconciling negative soil CO2 fluxes: Insights from a large-scale experimental hillslope. Soil Systems, 3(1), 10.
• Evaristo, J., Kim, M., Haren, J., Pangle, L. A., Harman, C. J., Troch, P. A., & McDonnell, J. J. (2019). Characterizing the fluxes and age distribution of soil water, plant water, and deep percolation in a model tropical ecosystem. Water Resources Research, 55(4), 3307--3327.
• Knighton, J., Souter-Kline, V., Volkmann, T., Troch, P. A., Kim, M., Harman, C. J., Morris, C., Buchanan, B., & Walter, M. T. (2019). Seasonal and topographic variations in ecohydrological separation within a small, temperate, snow-influenced catchment. Water Resources Research, 55(8), 6417--6435.
• Sengupta, A., Stegen, J. C., Meira, N., Wang, Y., Neilson, J. W., Tatarin, T., Hunt, E., Dontsova, K., Chorover, J., Troch, P. A., & others, . (2019). Assessing microbial community patterns during incipient soil formation from basalt. Journal of Geophysical Research: Biogeosciences, 124(4), 941--958.
• Wang, C., McNew, C. P., Lyon, S. W., Walter, M. T., Volkman, T. H., Abramson, N., Sengupta, A., Wang, Y., Neto, A., Pangle, L., & others, . (2019). Particle tracer transport in a sloping soil lysimeter under periodic, steady state conditions. Journal of Hydrology, 569, 61--76.
• Clark, M. P., Bahr, J., Bierkens, M., Cai, X., Hall, J., Hogue, T. S., Luce, C. H., Lundquist, J. D., Mackay, D. S., Meerveld, I., Rajaram, H., Sanchez-Vila, X. .., & Troch, P. A. (2018). Appreciation for Water Resources Research Reviewers. Water Resources Research, 54(10), 7114-7137.
• Troch, P. A., Dwivedi, R., Liu, T., Meira, N., Roy, T., Vald\'es-Pineda, R., Durcik, M., Arciniega-Esparza, S., & Bre\~na-Naranjo, J. A. (2018). Catchment-scale groundwater recharge and vegetation water use efficiency. Hydrology and Earth System Sciences Discussions, 1--46.
• Van, D., Troch, P. A., Booij, M. J., Niu, G., Volkmann, T. H., & Pangle, L. A. (2018). Effects of differential hillslope-scale water retention characteristics on rainfall--runoff response at the Landscape Evolution Observatory. Hydrological processes, 32(13), 2118--2127.
• Arciniega-Esparza, S. .., Bre??a-Naranjo, J., & Troch, P. A. (2017). On the connection between terrestrial and riparian vegetation: the role of storage partitioning in water-limited catchments. Hydrological Processes, 31(2), 489-494.
• Clark, M. P., Bahr, J. A., Bierkens, M., Cai, X., Hogue, T. S., Luce, C. H., Lundquist, J. D., Mackay, D. S., Meerveld, H., Rajaram, H., Sanchez-Vila, X. .., & Troch, P. A. (2017). A vision for Water Resources Research. Water Resources Research, 53(6), 4530-4532.
• Haren, J., Dontsova, K., Barron-Gafford, G. A., Troch, P. A., Chorover, J., Delong, S. B., Breshears, D. D., Huxman, T. E., Pelletier, J. D., Saleska, S. R., Zeng, X., & Ruiz, J. (2017). CO2 diffusion into pore spaces limits weathering rate of an experimental basalt landscape. Geology, 45(3), 203-206.
• Haren, J., Dontsova, K., Barron-Gafford, G. A., Troch, P. A., Chorover, J., Delong, S. B., Breshears, D. D., Huxman, T. E., Pelletier, J. D., Saleska, S. R., Zeng, X., & Ruiz, J. (2017). Erratum: CO2 diffusion into pore spaces limits weathering rate of an experimental basalt landscape [Geology, 45, (2016), (203-206)] doi: 10.1130/G38569.1. Geology, 45(5), 422-422.
• Pangle, L. A., Kim, M., Cardoso, C., Lora, M., Meira, N. A., Volkmann, T., Wang, Y., Troch, P. A., & Harman, C. J. (2017). The mechanistic basis for storage-dependent age distributions of water discharged from an experimental hillslope. Water Resources Research, 53(4), 2733-2754.
• Switanek, B. M., Troch, A. P., Castro, L. C., Leuprecht, A., Chang, H., Mukherjee, R., & Demaria, M. (2017). Scaled distribution mapping: A bias correction method that preserves raw climate model projected changes. Hydrology and Earth System Sciences, 21(6), 2649-2666.
• Brunke, M. A., Broxton, P., Pelletier, J., Gochis, D., Hazenberg, P., Lawrence, D. M., Leung, L. R., Niu, G., Troch, P. A., & Zeng, X. (2016). Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5). JOURNAL OF CLIMATE, 29(9), 3441-3461.
• Brunke, M. A., Broxton, P., Pelletier, J., Gochis, D., Hazenberg, P., Lawrence, D. M., Leung, L. R., Niu, G., Troch, P. A., & Zeng, X. (2016). Implementing and evaluating variable soil thickness in the Community Land Model, version 4.5 (CLM4.5). Journal of Climate, 29(9), 3441-3461.
• Hazenberg, P., Broxton, P., Gochis, D., Niu, G., Pangle, L. A., Pelletier, J. D., Troch, P. A., & Zeng, X. (2016). Testing the hybrid-3-D hillslope hydrological model in a controlled environment. Water Resources Research, 52(2), 1089-1107.
• Kim, M., Pangle, L. A., Cardoso, C., Lora, M., Volkmann, T., Wang, Y., Harman, C. J., & Troch, P. A. (2016). Transit time distributions and StorAge Selection functions in a sloping soil lysimeter with time-varying flow paths: Direct observation of internal and external transport variability. WATER RESOURCES RESEARCH, 52(9), 7105-7129.
• Kim, M., Pangle, L. A., Cardoso, C., Lora, M., Volkmann, T., Wang, Y., Harman, C. J., & Troch, P. A. (2016). Transit time distributions and StorAge Selection functions in a sloping soil lysimeter with time-varying flow paths: Direct observation of internal and external transport variability. Water Resources Research, 52(9), 7105-7129.
• Lora, M., Camporese, M., Troch, P. A., & Salandin, P. (2016). Rainfall-triggered shallow landslides: infiltration dynamics in a physical hillslope model. Hydrological Processes, 30(18), 3239-3251.
• Pelletier, J. D., Broxton, P. D., Hazenberg, P., Zeng, X., Troch, P. A., Niu, G., Williams, Z., Brunke, M. A., & Gochis, D. (2016). A gridded global data set of soil, intact regolith, and sedimentary deposit thicknesses for regional and global land surface modeling. JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, 8(1), 41-65.
• Pelletier, J. D., Broxton, P. D., Hazenberg, P., Zeng, X., Troch, P. A., Niu, G., Williams, Z., Brunke, M. A., & Gochis, D. (2016). A gridded global data set of soil, intact regolith, and sedimentary deposit thicknesses for regional and global land surface modeling. Journal of Advances in Modeling Earth Systems, 8(1), 41-65.
• Pohlmann, M., Dontsova, K. M., Root, R., Ruiz, J., Troch, P. A., & Chorover, J. D. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. Geochemistry, Geophysics, Geosystems, 17(6), 2054–2069.
• Pohlmann, M., Dontsova, K. M., Root, R., Ruiz, J., Troch, P. A., & Chorover, J. D. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. Geochemistry, Geophysics, Geosystems, 17, 2054-2069. doi:10.1002/2016GC006270
• Pohlmann, M., Dontsova, K., Root, R., Ruiz, J., Troch, P., & Chorover, J. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 17(6), 2054-2069.
• Pohlmann, M., Dontsova, K., Root, R., Ruiz, J., Troch, P., & Chorover, J. (2016). Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope. Geochemistry, Geophysics, Geosystems, 17(6), 2054-2069.
• Rasmussen, C., Troch, P. A., Pelletier, J. D., Swetnam, T. W., & Chorover, J. D. (2015). Quantifying topographic and vegetation effects on the trnasfer of energy and mass to a critical zone. Vadose Zone Journal.
• Sagarin, R. D., Adams, J., Blanchette, C. A., Brusca, R. C., Chorover, J., Cole, J. E., Micheli, F., Munguia-Vega, A. .., Rochman, C. M., Bonine, K., Haren, J., & Troch, P. A. (2016). Between control and complexity: opportunities and challenges for marine mesocosms. Frontiers in Ecology and the Environment, 14(7), 389-396.
• Sagarin, R. D., Adams, J., Blanchette, C. A., Brusca, R. C., Chorover, J., Cole, J. E., Micheli, F., Munguia-Vega, A., Rochman, C. M., Bonine, K., van, H. J., & Troch, P. A. (2016). Between control and complexity: opportunities and challenges for marine mesocosms. FRONTIERS IN ECOLOGY AND THE ENVIRONMENT, 14(7), 389-396.
• Sagarin, R., Sagarin, R., Troch, P. A., Troch, P. A., Adams, J., Adams, J., Brusca, R., Brusca, R., Blanchette, C., Blanchette, C., Chorover, J. D., Chorover, J. D., Cole, J. E., Cole, J. E., Micheli, F., Micheli, F., Munguia-Vega, A., Munguia-Vega, A., Rochman, C., , Rochman, C., et al. (2016). Between Control and Complexity: Opportunities and Challenges for Marine Mesocosms. Frontiers in Ecology and the Environment, 14, 389-396.
• Scudeler, C., Pangle, L., Pasetto, D., Niu, G., Volkmann, T., Paniconi, C., Putti, M., & Troch, P. (2016). Multiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory. HYDROLOGY AND EARTH SYSTEM SCIENCES, 20(10), 4061-4078.
• Scudeler, C., Pangle, L., Pasetto, D., Niu, G., Volkmann, T., Paniconi, C., Putti, M., & Troch, P. (2016). Multiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory. Hydrology and Earth System Sciences, 20(10), 4061-4078.
• Sengupta, A., Wang, Y., Meira, A. A., Matos, K., Dontsova, K. M., Root, R., Neilson, J. W., Chorover, J. D., Maier, R. M., & Troch, P. A. (2016). Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations. JoVE, e54536. doi:10.3791/54536
• Sengupta, A., Wang, Y., Meira, A. A., Matos, K., Dontsova, K. M., Root, R., Neilson, J. W., Chorover, J. D., Maier, R. M., & Troch, P. A. (2016). Soil lysimeter excavation for coupled hydrological, geochemical, and microbiological investigations. JoVE, 115(e54536). doi:10.3791/54536
• Sengupta, A., Wang, Y., Meira, N. A., Matos, K. A., Dontsova, K., Root, R., Neilson, J. W., Maier, R. M., Chorover, J., & Troch, P. A. (2016). Soil lysimeter excavation for coupled hydrological, geochemical, and microbiological investigations. Journal of Visualized Experiments, 2016(115).
• Van Haren, J. L., Dontsova, K. M., Barron-Gafford, G. A., Troch, P. A., Chorover, J. D., Saleska, S. R., DeLong, S., Huxman, T. E., Breshears, D. D., Zeng, X., Pelletier, J. D., & Ruiz, J. (2016). CO2 diffusion into pore spaces limits weathering rate of an experimental basalt landscape. Geology.
• Yoshida, T., & Troch, P. A. (2016). Coevolution of volcanic catchments in Japan. HYDROLOGY AND EARTH SYSTEM SCIENCES, 20(3), 1133-1150.
• Yoshida, T., & Troch, P. A. (2016). Coevolution of volcanic catchments in Japan. Hydrology and Earth System Sciences, 20(3), 1133-1150.
• Zapata-Rios, X. .., Brooks, P. D., Troch, P. A., McIntosh, J., & Guo, Q. (2016). Influence of terrain aspect on water partitioning, vegetation structure and vegetation greening in high-elevation catchments in northern New Mexico. Ecohydrology, 9(5), 782-795.
• Zapata-Rios, X., Brooks, P. D., Troch, P. A., McIntosh, J., & Guo, Q. (2016). Influence of terrain aspect on water partitioning, vegetation structure and vegetation greening in high-elevation catchments in northern New Mexico. ECOHYDROLOGY, 9(5), 782-795.
• Zapata-Rios, X., Brooks, P. D., Troch, P. A., McIntosh, J., & Rasmussen, C. (2016). Influence of climate variability on water partitioning and effective energy and mass transfer in a semi-arid critical zone. HYDROLOGY AND EARTH SYSTEM SCIENCES, 20(3), 1103-1115.
• Biederman, J. A., Somor, A. J., Harpold, A. A., Gutmann, E. D., Breshears, D. D., Troch, P. A., Gochis, D. J., Scott, R. L., Meddens, A., & Brooks, P. D. (2015). Recent tree die-off has little effect on streamflow in contrast to expected increases from historical studies. WATER RESOURCES RESEARCH, 51(12), 9775-9789.
• Biederman, J. A., Somor, A. J., Harpold, A. A., Gutmann, E. D., Breshears, D. D., Troch, P. A., Gochis, D. J., Scott, R. L., Meddens, A., & Brooks, P. D. (2015). Recent tree die-off has little effect on streamflow in contrast to expected increases from historical studies. Water Resources Research, 51(12), 9775-9789.
• Broxton, P. D., Harpold, A. A., Biederman, J. A., Troch, P. A., Molotch, N. P., & Brooks, P. D. (2015). Quantifying the effects of vegetation structure on snow accumulation and ablation in mixed-conifer forests. Ecohydrology, 8(6), 1073-1094.
• Field, J. P., Breshears, D. D., Law, D. J., Lopez Hoffman, L. -., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R., Mcintosh, J. C., Meixner, T. -., Niu, Y. -., Papuga, S. A., Pelletier, J. D., Rasmussen, C. -., & Troch, P. A. (2015). Critical zone services: Expanding context, constraints, and curency beyond ecosystem services.. Vadose Zone Journal, 1-7.
• Field, J. P., Breshears, D. D., Law, D. J., Villegas, J. C., Lopez-Hoffman, L. .., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R. A., McIntosh, J. C., Meixner, T., Niu, G., Papuga, S. A., Pelletier, J. D., Rasmussen, C. R., & Troch, P. A. (2015). Critical zone services: Expanding context, constraints, and currency beyond ecosystem services. Vadose Zone Journal, 14(1).
• Field, J. P., Breshears, D. D., Law, D. J., Villegas, J. C., Lopez-Hoffman, L., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R. A., McIntosh, J. C., Meixner, T., Niu, G., Papuga, S. A., Pelletier, J. D., Rasmussen, C. R., & Troch, P. A. (2015). Critical Zone Services: Expanding Context, Constraints, and Currency beyond Ecosystem Services. VADOSE ZONE JOURNAL, 14(1).
• Hazenberg, P., Fang, Y., Broxton, P., Gochis, D., Niu, G., Pelletier, J. D., Troch, P. A., & Zeng, X. (2015). A hybrid-3D hillslope hydrological model for use in Earth system models. Water Resources Research, 51(10), 8218-8239.
• Moore, G., McGuire, K., Troch, P., & Barron-Gafford, G. .. (2015). Ecohydrology and the Critical Zone: Processes and Patterns Across Scales. Developments in Earth Surface Processes, 19, 239-266.
• Pangle, L. A., DeLong, S. B., Abramson, N., Adams, J., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J., Dietrich, W. E., Dontsova, K., Durcik, M., Espeleta, J., Ferre, T., Ferriere, R., Henderson, W., Hunt, E. A., Huxman, T. E., Millar, D., Murphy, B., , Niu, G., et al. (2015). The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes. GEOMORPHOLOGY, 244, 190-203.
• Pangle, L. A., DeLong, S. B., Abramson, N., Adams, J., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J., Dietrich, W. E., Dontsova, K., Durcik, M., Espeleta, J., Ferre, T., Ferriere, R., Henderson, W., Hunt, E. A., Huxman, T. E., Millar, D., Murphy, B., , Niu, G., et al. (2015). The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes. Geomorphology, 244, 190-203.
• Pangle, L. A., Pangle, L. A., Delong, S. B., Delong, S. B., Abramson, N., Abramson, N., Adams, J., Adams, J., Barron-Gafford, G. A., Barron-Gafford, G. A., Breshears, D. D., Breshears, D. D., Brooks, P. D., Brooks, P. D., Chorover, J. D., Chorover, J. D., Dietrich, W. E., Dietrich, W. E., Dontsova, K. M., , Dontsova, K. M., et al. (2015). The Landscape Evolution Observatory: A large-scale controllable infrastructure to study Earth-surface processes.. Geomorphology, 244, 190-203.
• Pangle, L., DeLong, S., Abramson, N., Adams, J., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J. D., Dietrich, W. E., Dontsova, K. M., Durcik, M., Espeleta, J., Ferre, P. A., Ferriere, R. H., Henderson, W., Hunt, E., Huxman, T. E., Millar, D., Murphy, B., , Niu, Y., et al. (2015). The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes. Geomorphology, 244, 190-203.
  More info

  *
• Pasetto, D., Niu, G., Pangle, L., Paniconi, C., Putti, M., & Troch, P. A. (2015). Impact of sensor failure on the observability of flow dynamics at the Biosphere 2 LEO hillslopes. ADVANCES IN WATER RESOURCES, 86, 327-339.
• Pasetto, D., Niu, G., Pangle, L., Paniconi, C., Putti, M., & Troch, P. A. (2015). Impact of sensor failure on the observability of flow dynamics at the Biosphere 2 LEO hillslopes. Advances in Water Resources, 86, 327-339.
• Rasmussen, C., Pelletier, J. D., Troch, P. A., Swetnam, T. L., & Chorover, J. (2015). Quantifying Topographic and Vegetation Effects on the Transfer of Energy and Mass to the Critical Zone. VADOSE ZONE JOURNAL, 14(11).
• Rasmussen, C., Pelletier, J. D., Troch, P. A., Swetnam, T. L., & Chorover, J. (2015). Quantifying topographic and vegetation effects on the transfer of energy and mass to the critical zone. Vadose Zone Journal, 14(11).
• Salmoral, G., Willaarts, B. A., Troch, P. A., & Garrido, A. (2015). Drivers influencing streamflow changes in the Upper Tuna basin, Spain. SCIENCE OF THE TOTAL ENVIRONMENT, 503, 258-268.
• Salmoral, G., Willaarts, B. A., Troch, P. A., & Garrido, A. (2015). Drivers influencing streamflow changes in the Upper Turia basin, Spain. Science of the Total Environment, 503-504, 258-268.
• Troch, P. A., Lahmers, T., Meira, A., Mukherjee, R., Pedersen, J. W., Roy, T., & Vald??s-Pineda, R. (2015). Catchment coevolution: A useful framework for improving predictions of hydrological change?. Water Resources Research, 51(7), 4903-4922.
• Troch, P. A., Lahmers, T., Meira, A., Mukherjee, R., Pedersen, J. W., Roy, T., & Valdes-Pineda, R. (2015). Catchment coevolution: A useful framework for improving predictions of hydrological change?. WATER RESOURCES RESEARCH, 51(7), 4903-4922.
• Velde, Y., Heidb??chel, I., Lyon, S. W., Nyberg, L., Rodhe, A., Bishop, K., & Troch, P. A. (2015). Consequences of mixing assumptions for time-variable travel time distributions. Hydrological Processes, 29(16), 3460-3474.
• Zapata-Rios, X. .., McIntosh, J., Rademacher, L., Troch, P. A., Brooks, P. D., Rasmussen, C., & Chorover, J. (2015). Climatic and landscape controls on water transit times and silicate mineral weathering in the critical zone. Water Resources Research, 51(8), 6036-6051.
• Zapata-Rios, X. E., Brooks, P. D., Troch, P. A., & Mcintosh, J. C. (2015). Influence of terrain aspect on water partitioning, vegetation structure, and vegetation greening in high elevation catchments in northern New Mexico. Ecohydrology. doi:10.1002/eco.1674
• Zapata-Rios, X., McIntosh, J., Rademacher, L., Troch, P. A., Brooks, P. D., Rasmussen, C., & Chorover, J. (2015). Climatic and landscape controls on water transit times and silicate mineral weathering in the critical zone. WATER RESOURCES RESEARCH, 51(8), 6036-6051.
• van, d., Heidbuechel, I., Lyon, S. W., Nyberg, L., Rodhe, A., Bishop, K., & Troch, P. A. (2015). Consequences of mixing assumptions for time-variable travel time distributions. HYDROLOGICAL PROCESSES, 29(16), 3460-3474.
• Band, L. E., McDonnell, J. J., Duncan, J. M., Barros, A., Bejan, A., Burt, T., Dietrich, W. E., Emanuel, R. E., Hwang, T., Katul, G., Kim, Y., McGlynn, B., Miles, B., Porporato, A., Scaife, C., & Troch, P. A. (2014). Ecohydrological flow networks in the subsurface. Ecohydrology, 7(4), 1073-1078.
• Broxton, P. D., Zeng, X., Scheftic, W., & Troch, P. A. (2014). A MODIS-Based Global 1-km Maximum Green Vegetation Fraction Dataset. JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY, 53(8), 1996-2004.
• Broxton, P. D., Zeng, X., Scheftic, W., & Troch, P. A. (2014). A MODIS-based global 1-km maximum green vegetation fraction dataset. Journal of Applied Meteorology and Climatology, 53(8), 1996-2004.
• Broxton, P. D., Zeng, X., Sulla-Menashe, D. .., & Troch, P. A. (2014). A global land cover climatology using MODIS data. Journal of Applied Meteorology and Climatology, 53(6), 1593-1605.
• Broxton, P. D., Zeng, X., Sulla-Menashe, D., & Troch, P. A. (2014). A Global Land Cover Climatology Using MODIS Data. JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY, 53(6), 1593-1605.
• Broxton, P., Troch, P. A., Schaffner, M., Unkrich, C., & Goodrich, D. (2014). AN ALL-SEASON FLASH FLOOD FORECASTING SYSTEM FOR REAL-TIME OPERATIONS. BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 95(3), 399-407.
• Broxton, P., Troch, P. A., Schaffner, M., Unkrich, C., & Goodrich, D. (2014). AN all-season flash flood forecasting system for real-time operations. Bulletin of the American Meteorological Society, 95(3), 399-407.
• Chorover, J. D., Gavaert, A., Tueling, A. J., Uijlenhoet, R., DeLong, S. B., Huxman, T. E., Pangle, L., Brashears, D. D., Pelletier, J. D., Saleska, S. R., Zeng, X., & Troch, P. A. (2014). Hillslope-scale experiment demonstrates the role of convergence during two-step saturation. Hydrol. Earth Syst. Sci., 18, 1-12.
• Chorover, J. D., Perdrial, J., McIntosh, J., Harpold, A., Brooks, P. D., Zapata-Rios, X., Ray, J., Kanduc, T., Litvak, M., Troch, P. A., & Meixner, T. (2014). Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes. Biogeochem, 118, 273-290.
• Creutzfeldt, B., Troch, P. A., G??ntner, A., Ferr??, T., Graeff, T., & Merz, B. (2014). Storage-discharge relationships at different catchment scales based on local high-precision gravimetry. Hydrological Processes, 28(3), 1465-1475.
• Creutzfeldt, B., Troch, P. A., Guentner, A., Ferre, T., Graeff, T., & Merz, B. (2014). Storage-discharge relationships at different catchment scales based on local high-precision gravimetry. HYDROLOGICAL PROCESSES, 28(3), 1465-1475.
• Field, J. P., Breshears, D. D., Law, D. J., Lopez Hoffman, L. -., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R., Mcintosh, J. C., Meixner, T. -., Niu, Y. -., Papuga, S. A., Pelletier, J. D., Rasmussen, C. -., & Troch, P. A. (2014). A perspective on areas of emphasis for critical zone services. Vadose Zone Journal.
• Field, J. P., Breshears, D. D., Law, D. J., Lopez Hoffman, L. -., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R., Mcintosh, J. C., Meixner, T. -., Niu, Y. -., Papuga, S. A., Pelletier, J. D., Rasmussen, C. -., & Troch, P. A. (2014). Critical zone services: Expanding context, constraints, and curency beyond ecosystem services.. Vadose Zone Journal, 1-7.
• Field, J. P., Breshears, D. D., Law, D. J., Villegas, J., Lopez Hoffman, L. -., Brooks, P. D., Chorover, J., Barron-Gafford, G. A., Gallery, R. E., Litvak, M. E., Lybrand, R., Mcintosh, J. C., Meixner, T. -., Niu, Y. -., Papuga, S. A., Pelletier, J. D., Rasmussen, C. -., & Troch, P. A. (2014). Critical Zone Services: Expanding Context, Constraints, and Currency beyond Ecosystem Services. Vadose Zone Journal.
• Gevaert, A. I., Teuling, A. J., Uijlenhoet, R., DeLong, S. B., Huxman, T. E., Pangle, L. A., Breshears, D. D., Chorover, J., Pelletier, J. D., Saleska, S. R., Zeng, X., & Troch, P. A. (2014). Hillslope-scale experiment demonstrates the role of convergence during two-step saturation. Hydrology and Earth System Sciences, 18(9), 3681-3692.
• Harman, C. J., Lohse, K. A., Troch, P. A., & Sivapalan, M. (2014). Spatial patterns of vegetation, soils, and microtopography from terrestrial laser scanning on two semiarid hillslopes of contrasting lithology. JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES, 119(2), 163-180.
• Harman, C. J., Lohse, K. A., Troch, P. A., & Sivapalan, M. (2014). Spatial patterns of vegetation, soils, and microtopography from terrestrial laser scanning on two semiarid hillslopes of contrasting lithology. Journal of Geophysical Research G: Biogeosciences, 119(2), 163-180.
  More info

  Abstract: Shrublands in semiarid regions are heterogeneous landscapes consisting of infertile bare areas separated by nutrient rich vegetated areas known as resource islands. Spatial patterns in these landscapes are structured by feedbacks driven by the transport of water and nutrient resources from the intershrub space to areas below shrubs, and the retention of these resources to locally drive productivity and tight biogeochemical cycles. Most understanding of plant-soil feedbacks is based predominantly on studies of low topographic gradient landscapes, and it is unclear whether the patterns of association between soils and vegetation, and the autogenic processes that create them, also occur on more steeply sloping terrain. Here we analyze the spatial patterns of soils, vegetation, and microtopography on hillslopes of contrasting lithology (one granite at 16°, one schist at 27°) in the Sonoran desert foothills of the Catalina Mountains. We also describe a method of extracting vegetation density from terrestrial laser scanning point cloud data at 5 cm × 5 cm scales and find that it correlates well with soil organic carbon measurements. Vegetation was associated with microtopographic mounds (relative to the mean slope) extending 0.3 m downslope and 1.8 m (schist) and 0.9 m (granite) upslope on the study hillslopes. Soils below the shrub canopies exhibited 2-3 times more soil organic matter and 2-4 times higher hydraulic conductivity than the interspaces. Soils enriched with organic matter were found to extend at least two canopy radii downslope of woody shrubs, but not upslope. These plumes were clearest in the lower gradient granite site where vegetation mounds created distinct patterns of microtopographic convergence and divergence. At the steeper schist site, microtopography appeared to have a weaker control on topographic flow accumulation. Collectively, our findings suggest that the spatial structure of association between soils and microtopography and vegetation on these slopes exhibit many of the features observed in lower gradient areas. However, microtopography and soils are more asymmetric along the downslope axis of the hillslopes than lower gradient areas and vary with lithology. Alluvial and colluvial processes are likely more important in shaping vegetation and soil dynamics on hillslopes, and these factors need further consideration in scaling results to the landscape level. Key Points Resource island properties on two rangeland slopes are distinct from interspace New index of vegetation density from TLS correlates with other properties Distinct asymmetry in resource island shape suggests geomorphic control ©2014. American Geophysical Union. All Rights Reserved.
• Harman, C., & Troch, P. A. (2014). What makes Darwinian hydrology "darwinian"? Asking a different kind of question about landscapes. Hydrology and Earth System Sciences, 18(2), 417-433.
  More info

  Abstract: There have been repeated calls for a Darwinian approach to hydrologic science, or for a synthesis of Darwinian and Newtonian approaches, to deepen understanding of the hydrologic system in the larger landscape context, and so develop a better basis for predictions now and in an uncertain future. But what exactly makes a Darwinian approach to hydrology "Darwinian"? While there have now been a number of discussions of Darwinian approaches, many referencing Harte (2002), the term is potentially a source of confusion because its connections to Darwin remain allusive rather than explicit. Here we suggest that the Darwinian approach to hydrology follows the example of Charles Darwin by focusing attention on the patterns of variation in populations and seeking hypotheses that explain these patterns in terms of the mechanisms and conditions that determine their historical development. These hypotheses do not simply catalog patterns or predict them statistically - they connect the present structure with processes operating in the past. Nor are they explanations presented without independent evidence or critical analysis - Darwin's hypotheses about the mechanisms underlying present-day variation could be independently tested and validated. With a Darwinian framework in mind, it is easy to see that a great deal of hydrologic research has already been done that contributes to a Darwinian hydrology - whether deliberately or not. We discuss some practical and philosophical issues with this approach to hydrologic science: how are explanatory hypotheses generated? What constitutes a good hypothesis? How are hypotheses tested? "Historical" sciences - including paleohydrology - have long grappled with these questions, as must a Darwinian hydrologic science. We can draw on Darwin's own example for some answers, though there are ongoing debates about the philosophical nature of his methods and reasoning. Darwin used a range of methods of historical reasoning to develop explanatory hypotheses: extrapolating mechanisms, space for time substitution, and looking for signatures of history. Some of these are already in use, while others are not and could be used to develop new insights. He sought explanatory hypotheses that intelligibly unified disparate facts, were testable against evidence, and had fertile implications for further research. He provided evidence to support his hypotheses by deducing corollary conditions ("if explanation A is true, then B will also be true") and comparing these to observations. While a synthesis of the Darwinian and Newtonian approaches remains a goal, the Darwinian approach to hydrologic science has significant value of its own. The Darwinian hydrology that has been conducted already has not been coordinated or linked into a general body of theory and knowledge, but the time is coming when this will be possible. © Author(s) 2014.
• Niu, G., Paniconi, C., Troch, P. A., Scott, R. L., Durcik, M., Zeng, X., Huxman, T., & Goodrich, D. C. (2014). An integrated modelling framework of catchment- scale ecohydrological processes: 1. Model description and tests over an energy- limited watershed. ECOHYDROLOGY, 7(2), 427-439.
• Niu, G., Paniconi, C., Troch, P. A., Scott, R. L., Durcik, M., Zeng, X., Huxman, T., & Goodrich, D. C. (2014). An integrated modelling framework of catchment-scale ecohydrological processes: 1. Model description and tests over an energy-limited watershed. Ecohydrology, 7(2), 427-439.
  More info

  Abstract: The interactions between atmospheric, hydrological, and ecological processes at various spatial and temporal scales are not fully represented in most ecohydrological models. This first of a two-part paper documents a fully integrated catchment-scale ecohydrological model consisting of a three-dimensional physically based hydrological model and a land surface model. This first part also presents a first application to test the model over an energy-limited catchment (8.4km2) of the Sleepers River watershed in Vermont. The physically based hydrological model (CATchment HYdrology, CATHY) describes three-dimensional subsurface flow in variably saturated porous media and surface routing on hillslopes and in stream channels, whereas the land surface model (LSM), an augmented version of Noah LSM with multiple parameterization schemes (NoahMP), accounts for energy, water, and carbon flux exchanges between various land surface elements and the atmosphere. CATHY and NoahMP are coupled through exchanges of water fluxes and states. In the energy-limited catchment of the Sleepers River watershed, where snowmelt runoff generation is the dominant hydrologic flux, the coupled CATHY/NoahMP model at both 90 and 30-m surface grid resolutions, with minimal calibration, performs well in simulating the observed snow accumulation, and melt and subsequent snowmelt discharge. The Nash-Sutcliffe model efficiency of daily discharge is above 0.82 for both resolutions. The simulation at 90-m resolution shows a marginal improvement over that at 30-m resolution because of more elaborate calibration of model parameters. The coupled CATHY/NoahMP also shows a capability of simulating surface-inundated area and distributed surface water height, although the accuracy of these simulations needs further evaluation. The CATHY/NoahMP model is thus also a potentially useful research tool for predicting flash flood and lake dynamics under climatic change. © 2013 John Wiley & Sons, Ltd.
• Niu, G., Pasetto, D., Scudeler, C., Paniconi, C., Putti, M., Troch, P. A., DeLong, S. B., Dontsova, K., Pangle, L., Breshears, D. D., Chorover, J., Huxman, T. E., Pelletier, J., Saleska, S. R., & Zeng, X. (2014). Incipient subsurface heterogeneity and its effect on overland flow generation – insight from a modeling study of the first experiment at the Biosphere 2 Landscape Evolution Observatory. Hydrology and Earth System Sciences.
• Niu, G., Pasetto, D., Scudeler, C., Paniconi, C., Putti, M., Troch, P. A., Delong, S. B., Dontsova, K., Pangle, L., Breshears, D. D., Chorover, J., Huxman, T. E., Pelletier, J., Saleska, S. R., & Zeng, X. (2014). Incipient subsurface heterogeneity and its effect on overland flow generation - Insight from a modeling study of the first experiment at the Biosphere 2 Landscape Evolution Observatory. Hydrology and Earth System Sciences, 18(5), 1873-1883.
• Niu, G., Troch, P. A., Paniconi, C., Scott, R. L., Durcik, M., Zeng, X., Huxman, T., Goodrich, D., & Pelletier, J. (2014). An integrated modelling framework of catchment- scale ecohydrological processes: 2. The role of water subsidy by overland flow on vegetation dynamics in a semi- arid catchment. ECOHYDROLOGY, 7(2), 815-827.
• Niu, G., Troch, P. A., Paniconi, C., Scott, R. L., Durcik, M., Zeng, X., Huxman, T., Goodrich, D., & Pelletier, J. (2014). An integrated modelling framework of catchment-scale ecohydrological processes: 2. The role of water subsidy by overland flow on vegetation dynamics in a semi-arid catchment. Ecohydrology, 7(2), 815-827.
  More info

  Abstract: In water-limited regions, surface water and carbon fluxes are strongly controlled by soil water availability, which may be highly variable at very small spatial scales (e.g. metres) because of variations in terrain, soils, and vegetation conditions and to processes of water redistribution along hillslopes. This second of a two-part paper first evaluates the performance of a newly developed ecohydrological model over a small semi-arid experimental catchment (7·92ha) in southeastern Arizona. Secondly, it investigates the effects of soil properties on water subsidy resulting from lateral overland flow re-infiltration and on overall ecohydrological response. With optimized parameters, the model shows a higher ability to simulate surface energy and water fluxes than CO2 fluxes at all temporal scales. The model simulates observed CO2 fluxes fairly well at diurnal scales during the main growing seasons and the interannual variability of these fluxes in response to soil moisture variations from drought years to wet years. However, the model reproduces less well carbon assimilation in spring and positive CO2 flux pulses following early monsoon rain events, suggesting a need for further development of the model's representations of multiple plant species and soil carbon decomposition. The model simulates soil moisture at 5cm much better than at 15cm mainly because of heterogeneous soil properties. Through five numerical experiments with varying saturated hydraulic conductivity values, it is revealed that the discharge at the outlet of this semi-arid catchment is essentially attributed to lateral overland flow that is generated mainly by infiltration-excess runoff. Subsurface flow plays a minor role in this semi-arid catchment with a very deep groundwater table (>100m). The model produces wetter soils in lowland areas along stream rills and channels through re-infiltration of lateral overland flow. This water subsidy provides plants with favourable conditions to produce more leaves, CO2, and ET fluxes in lowland areas. Re-infiltration of overland flow over complex terrain may play a role in buffering climatic impacts in a warming climate with fewer but more intense rainfall events in the Southwestern United States. © 2013 John Wiley & Sons, Ltd.
• Niu, Y., Pasetto, D., Scudeler, C., Paniconi, C., Putti, M., Troch, P. A., DeLong, S., Dontsova, K. M., Pangle, L., Breshears, D. D., Chorover, J. D., Huxman, T. E., Pelletier, J. D., Saleska, S. R., & Zeng, X. (2014). Incipient subsurface heterogeneity and its effect on overland flow generation -- insight from a modeling study of the first experiment at the Biosphere 2 Landscape Evolution Observatory. Hydrol. Earth Syst. Sci., 18, 1873-1883.
  More info

  *
• Pangle, L., DeLong, S., Abramson, N., Adams, J., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J. D., Dietrich, W. E., Dontsova, K. M., Durcik, M., Espeleta, J., Ferre, P. A., Ferriere, R. H., Henderson, W., Hunt, E., Huxman, T. E., Millar, D., Murphy, B., , Niu, Y., et al. (2015). The Landscape Evolution Observatory: A large-scale controllable infrastructure to study coupled Earth-surface processes. Geomorphology.
  More info

  *
• Perdrial, J. N., McIntosh, J., Harpold, A., Brooks, P. D., Zapata-Rios, X. .., Ray, J., Meixner, T., Kanduc, T., Litvak, M., Troch, P. A., & Chorover, J. (2014). Stream water carbon controls in seasonally snow-covered mountain catchments: Impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes. Biogeochemistry, 118(1-3), 273-290.
• Perdrial, J. N., McIntosh, J., Harpold, A., Brooks, P. D., Zapata-Rios, X., Ray, J., Meixner, T., Kanduc, T., Litvak, M., Troch, P. A., & Chorover, J. (2014). Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes. BIOGEOCHEMISTRY, 118(1-3), 273-290.
• Rajagopal, S., Dominguez, F., Gupta, H. V., Troch, P. A., & Castro, C. L. (2014). Physical Mechanisms Related to Climate-Induced Drying of Two Semiarid Watersheds in the Southwestern United States. JOURNAL OF HYDROMETEOROLOGY, 15(4), 1404-1418.
• Rajagopal, S., Dominguez, F., Gupta, H. V., Troch, P. A., & Castro, C. L. (2014). Physical mechanisms related to climate-induced drying of two semi-arid watersheds in the southwest US. Journal of Hydrometeorology, 15.
  More info

  doi:10.1175/JHM-D-13-0106.1
• Sawicz, K. A., Kelleher, C., Wagener, T., Troch, P., Sivapalan, M., & Carrillo, G. (2014). Characterizing hydrologic change through catchment classification. Hydrology and Earth System Sciences, 18(1), 273-285.
  More info

  Abstract: There has been an intensive search in recent years for suitable strategies to organize and classify the very heterogeneous group of catchments that characterize our landscape. One strand of this work has focused on testing the value of hydrological signatures derived from widely available hydro-meteorological observations for this catchment classification effort. Here we extend this effort by organizing 314 catchments across the contiguous US into 12 distinct clusters using six signature characteristics for a baseline decade (1948-1958, period 1). We subsequently develop a regression tree and utilize it to classify these catchments for three subsequent decades (periods 2-4). This analysis allows us to assess the movement of catchments between clusters over time, and therefore to assess whether their hydrologic similarity/dissimilarity changes. We find examples in which catchments initially assigned to a single class diverge into multiple classes (e.g., midwestern catchments between periods 1 and 2), but also cases where catchments from different classes would converge into a single class (e.g., midwestern catchments between periods 2 and 3). We attempt to interpret the observed changes for causes of this temporal variability in hydrologic behavior. Generally, the changes in both directions were most strongly controlled by changes in the water balance of catchments characterized by an aridity index close to one. Changes to climate characteristics of catchments-mean annual precipitation, length of cold season or the seasonality of precipitation throughout the year-seem to explain most of the observed class transitions between slightly water-limited and slightly energy-limited states. Inadequate temporal information on other time-varying aspects, such as land use change, limits our ability to further disentangle causes for change. © 2014 Author(s).
• Vereecken, H., Young, M., Troch, P., & Bertsch, P. (2014). Strategies to observe and understand processes and drivers in the biogeosphere: AGU Chapman conference on soil-mediated drivers of coupled biogeochemical and hydrological processes across scales; Tucson, Arizona, 21-24 October 2013. Eos, 95(2), 16.
• Heidbuechel, I., Troch, P. A., & Lyon, S. W. (2013). Separating physical and meteorological controls of variable transit times in zero-order catchments. WATER RESOURCES RESEARCH, 49(11), 7644-7657.
• Heidbüchel, I., Troch, P. A., & Lyon, S. W. (2013). Separating physical and meteorological controls of variable transit times in zero-order catchments. Water Resources Research, 49(11), 7644-7657.
  More info

  Abstract: We observed water fluxes and isotopic compositions within the subsurface of six small nested zero-order catchments over the course of three North American monsoon seasons and found that mean transit times (mTTs) were variable between seasons and different spatial patterns of mTTs emerged each year. For each monsoon season, it was possible to correlate mTTs with a different physical catchment property. In 2007, mTTs correlated best with mean soil depth, in 2008 soil hydraulic conductivity gained importance in explaining the variability and in 2009 planform curvature showed the best correlation. Differences in meteorological forcing between the three monsoon seasons explained the temporal variability of mTTs. In 2007, a series of precipitation events caused the storage capacity of the soils of some of the zero-order catchments to be exceeded. As a result those catchments started producing quick runoff (overland and macropore flow). In 2008, precipitation events were more evenly distributed throughout the season, soils did not saturate, runoff coefficients decreased because more water left the catchment via evapotranspiration and soil hydraulic conductivity became a stronger control since matrix flow dominated. The 2009 monsoon was unusually dry, the soil storage became depleted and water flowed mainly through bedrock pathways. Therefore, topographic parameters gained importance in determining how quickly water arrived at the catchment outlet. In order to improve our understanding of what controls mTTs we suggest a dimensionless number that helps identifying partitioning thresholds and sorts precipitation events into one of the three response modes that were observed in our zero-order catchments. Key Points Inherent catchment properties and external forcings control transit times External forcings sort precipitation events into specific response domains Inherent catchment properties control transit times within these domains ©2013. American Geophysical Union. All Rights Reserved.
• Hrachowitz, M., Savenije, H., Bl??schl, G., McDonnell, J. J., Sivapalan, M., Pomeroy, J. W., Arheimer, B., Blume, T., Clark, M. P., Ehret, U., Fenicia, F., Freer, J. E., Gelfan, A., Gupta, H. V., Hughes, D. A., Hut, R. W., Montanari, A., Pande, S., Tetzlaff, D., , Troch, P. A., et al. (2013). A decade of Predictions in Ungauged Basins (PUB)-a review. Hydrological Sciences Journal, 58(6), 1198-1255.
• Le, H. D., Schutter, G. D., Kadri, E. H., Aggoun, S., Vierendeels, J., Tichko, S., & Troch, P. (2013). Computational fluid dynamics calibration of Tattersall MK-II type rheometer for concrete. Applied Rheology, 23(3).
  More info

  Abstract: Currently more and more researches have been performing concerning the numerical simulation of the behavior of fresh concrete during pumping or formwork filling. Adequate implementation of the rheology properties of fresh concrete is a determinant key to obtain realistic simulations. However, in many cases, the rheological parameters of the fresh concrete as determined by rheometers are not sufficiently accurate. The common principle of all the rheometers is not to measure directly the rheological parameters of concrete but to measure some basic physical parameters (torque, velocity, pressure,...) that that in some cases allow the calculation of the rheological parameter in terms of fundamental physical quantities. Errors can be caused by undesired flow phenomena which are not taken into the prediction formulas and by the inaccurate prediction formulas themselves. This is directly related to the poor calibration of the rheometer that cannot cover all ranges of materials. This paper investigates the calibration of the Tattersall MK-II rheometer by performing the numerical simulation for a tremendous range of concrete flowing in the rheometer, using computational fluid dynamics (CFD). This allows to quickly and accurately obtain the rheological properties of fresh concrete, which can then be used consistently for further flow simulations. This method can be applied for all types of rheometer.
• Pelletier, J. D., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J., Durcik, M., Harman, C. J., Huxman, T. E., Lohse, K. A., Lybrand, R., Meixner, T., McIntosh, J. C., Papuga, S. A., Rasmussen, C., Schaap, M., Swetnam, T. L., & Troch, P. A. (2013). Coevolution of nonlinear trends in vegetation, soils, and topography with elevation and slope aspect: A case study in the sky islands of southern Arizona. JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 118(2), 741-758.
• Pelletier, J. D., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J., Durcik, M., Harman, C. J., Huxman, T. E., Lohse, K. A., Lybrand, R., Meixner, T., McIntosh, J. C., Papuga, S. A., Rasmussen, C., Schaap, M., Swetnam, T. L., & Troch, P. A. (2013). Coevolution of nonlinear trends in vegetation, soils, and topography with elevation and slope aspect: A case study in the sky islands of southern Arizona. Journal of Geophysical Research: Earth Surface, 118(2), 741-758.
• Pelletier, J. D., Barron-Gafford, G. A., Breshears, D. D., Brooks, P. D., Chorover, J., Durcik, M., Harman, C. J., Huxman, T. E., Lohse, K. A., Lybrand, R., Meixner, T., Mcintosh, J. C., Papuga, S. A., Rasmussen, C., Schaap, M. G., Swetnam, T. W., & Troch, P. A. (2013). Coevolution of nonlinear trends in vegetation, soils, and topography with elevation and slope aspect: A case study in the sky islands of southern Arizona. J. Geophys. Res. - Earth Surf., 118, 741-758.
• Pelletier, J. D., Pelletier, J. D., Breshears, D. D., Breshears, D. D., Barron-Gafford, G. A., Barron-Gafford, G. A., Brooks, P. D., Brooks, P. D., Chorover, J., Chorover, J. D., Durick, M., Durick, M., Harman, C. J., Harman, C. J., Huxman, T. E., Huxman, T. E., Lohse, K. A., Lohse, K. A., Lybrand, R., , Lybrand, R., et al. (2013). Coevolution of nonlinear trends in vegetation, soils, and topography with elevation and slope aspect: A case study in the sky islands of southern Arizona. Journal of Geophysical Research - Earth Surface, 118(2), 1-18.
• Roo, S. D., & Troch, P. (2013). Field monitoring of ship wave action on environmentally friendly bank protection in a confined waterway. Journal of Waterway, Port, Coastal and Ocean Engineering, 139(6), 527-534.
  More info

  Abstract: The road toward a sustainable inland waterway network entails the installation of ecologically sound and technically effective bank protection. Heavy shipping traffic complicates the development of environmentally friendly bank protection on confined, nontidal waterways. Because in such conditions ship waves vary with ship design and operation, with topographic boundaries and locally changing hydraulic conditions, ship wave action is poorly understood. Therefore, a stand-alone field monitoring system was designed that accurately measures the impact on and response of environmentally friendly bank protection, consisting of off-bank timber piling and vegetation (reeds). Subsequently, the instrumentation was re-engineered and extended to a mobile version, enhancing the dynamic measurement possibilities. In this paper, the setup of both measurement systems is described, together with a detailed overview of the selected measurement instrumentation and good installation practices. The added value of these field monitoring systems is illustrated with an example of the monitoring system's data output. © 2013 American Society of Civil Engineers.
• Troch, P. A., Berne, A., Bogaart, P., Harman, C., G., A., Lyon, S. W., Paniconi, C., R., V., Rupp, D. E., Selker, J. S., Teuling, A. J., Uijlenhoet, R., & E., N. (2013). The importance of hydraulic groundwater theory in catchment hydrology: The legacy of Wilfried Brutsaert and Jean-Yves Parlange. Water Resources Research, 49(9), 5099-5116.
  More info

  Abstract: Based on a literature overview, this paper summarizes the impact and legacy of the contributions of Wilfried Brutsaert and Jean-Yves Parlange (Cornell University) with respect to the current state-of-the-art understanding in hydraulic groundwater theory. Forming the basis of many applications in catchment hydrology, ranging from drought flow analysis to surface water-groundwater interactions, hydraulic groundwater theory simplifies the description of water flow in unconfined riparian and perched aquifers through assumptions attributed to Dupuit and Forchheimer. Boussinesq (1877) derived a general equation to study flow dynamics of unconfined aquifers in uniformly sloping hillslopes, resulting in a remarkably accurate and applicable family of results, though often challenging to solve due to its nonlinear form. Under certain conditions, the Boussinesq equation can be solved analytically allowing compact representation of soil and geomorphological controls on unconfined aquifer storage and release dynamics. The Boussinesq equation has been extended to account for flow divergence/convergence as well as for nonuniform bedrock slope (concave/convex). The extended Boussinesq equation has been favorably compared to numerical solutions of the three-dimensional Richards equation, confirming its validity under certain geometric conditions. Analytical solutions of the linearized original and extended Boussinesq equations led to the formulation of similarity indices for baseflow recession analysis, including scaling rules, to predict the moments of baseflow response. Validation of theoretical recession parameters on real-world streamflow data is complicated due to limited measurement accuracy, changing boundary conditions, and the strong coupling between the saturated aquifer with the overlying unsaturated zone. However, recent advances are shown to have mitigated several of these issues. The extended Boussinesq equation has been successfully applied to represent baseflow dynamics in catchment-scale hydrological models, and it is currently considered to represent lateral redistribution of groundwater in land surface schemes applied in global circulation models. From the review, it is clear that Wilfried Brutsaert and Jean-Yves Parlange stimulated a body of research that has led to several fundamental discoveries and practical applications with important contributions in hydrological modeling. ©2013. American Geophysical Union. All Rights Reserved.
• Troch, P. A., Berne, A., Bogaart, P., Harman, C., Hilberts, A., Lyon, S. W., Paniconi, C., Pauwels, V., Rupp, D. E., Selker, J. S., Teuling, A. J., Uijlenhoet, R., & Verhoest, N. (2013). The importance of hydraulic groundwater theory in catchment hydrology: The legacy of Wilfried Brutsaert and Jean-Yves Parlange. WATER RESOURCES RESEARCH, 49(9), 5099-5116.
• Troch, P. A., Berne, A., Bogaart, P., Harman, C., Hilberts, A., Lyon, S. W., Paniconi, C., Pauwels, V., Rupp, D. E., Selker, J. S., Teuling, A. J., Uijlenhoet, R., & Verhoest, N. (2013). The importance of hydraulic groundwater theory in catchment hydrology: The legacy of Wilfried Brutsaert and Jean-Yves Parlange. Water Resources Research, 49(9), 5099-5116.
• Troch, P. A., Carrillo, G., Sivapalan, M., Wagener, T., & Sawicz, K. (2013). Climate-vegetation-soil interactions and long-term hydrologic partitioning: Signatures of catchment co-evolution. Hydrology and Earth System Sciences, 17(6), 2209-2217.
  More info

  Abstract: Budyko (1974) postulated that long-term catchment water balance is controlled to first order by the available water and energy. This leads to the interesting question of how do landscape characteristics (soils, geology, vegetation) and climate properties (precipitation, potential evaporation, number of wet and dry days) interact at the catchment scale to produce such a simple and predictable outcome of hydrological partitioning? Here we use a physically-based hydrologic model separately parameterized in 12 US catchments across a climate gradient to decouple the impact of climate and landscape properties to gain insight into the role of climate-vegetation-soil interactions in long-term hydrologic partitioning. The 12 catchment models (with different paramterizations) are subjected to the 12 different climate forcings, resulting in 144 10 yr model simulations. The results are analyzed per catchment (one catchment model subjected to 12 climates) and per climate (one climate filtered by 12 different model parameterization), and compared to water balance predictions based on Budyko's hypothesis (E/P = φ(Ep/P); E: evaporation, P: precipitation, Ep: potential evaporation). We find significant anti-correlation between average deviations of the evaporation index (E/P) computed per catchment vs. per climate, compared to that predicted by Budyko. Catchments that on average produce more E/P have developed in climates that on average produce less E/P, when compared to Budyko's prediction. Water and energy seasonality could not explain these observations, confirming previous results reported by Potter et al. (2005). Next, we analyze which model (i.e., landscape filter) characteristics explain the catchment's tendency to produce more or less E/P. We find that the time scale that controls subsurface storage release explains the observed trend. This time scale combines several geomorphologic and hydraulic soil properties. Catchments with relatively longer subsurface storage release time scales produce significantly more E/P. Vegetation in these catchments have longer access to this additional groundwater source and thus are less prone to water stress. Further analysis reveals that climates that give rise to more (less) E/P are associated with catchments that have vegetation with less (more) efficient water use parameters. In particular, the climates with tendency to produce more E/P have catchments that have lower % root fraction and less light use efficiency. Our results suggest that their exists strong interactions between climate, vegetation and soil properties that lead to specific hydrologic partitioning at the catchment scale. This co-evolution of catchment vegetation and soils with climate needs to be further explored to improve our capabilities to predict hydrologic partitioning in ungauged basins. © Author(s) 2013.
• Bachmair, S., Weiler, M., & Troch, P. A. (2012). Intercomparing hillslope hydrological dynamics: Spatio-temporal variability and vegetation cover effects. Water Resources Research, 48(5).
• Creutzfeldt, B., Ferr??, T., Troch, P., Merz, B., Wziontek, H., & G??ntner, A. (2012). Total water storage dynamics in response to climate variability and extremes: Inference from long-term terrestrial gravity measurement. Journal of Geophysical Research Atmospheres, 117(8).
• Creutzfeldt, B., Ferre, T. y., Troch, P., Merz, B., Wziontek, H., & Guentner, A. (2012). Total water storage dynamics in response to climate variability and extremes: Inference from long-term terrestrial gravity measurement. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 117.
• Guardiola-Claramonte, M. .., Troch, P. A., Breshears, D. D., Huxman, T. E., Switanek, M. B., Durcik, M., & Cobb, N. S. (2012). Corrigendum to " Decreased streamflow in semi-arid basins following drought-induced tree die-off: A counter-intuitive and indirect climate impact on hydrology" [J. Hydrol. 406 (3-4) (2011) 225-233]. Journal of Hydrology, 414-415, 560.
• Guardiola-Claramonte, M., Troch, P. A., Breshears, D. D., Huxman, T. E., Switanek, M. B., Durcik, M., & Cobb, N. S. (2012). Corrigendum to " Decreased streamflow in semi-arid basins following drought-induced tree die-off: A counter-intuitive and indirect climate impact on hydrology" [J. Hydrol. 406 (3-4) (2011) 225-233]. Journal of Hydrology, 414-415, 560-.
• Guardiola-Claramonte, M., Troch, P. A., Breshears, D. D., Huxman, T. E., Switanek, M. B., Durcik, M., & Cobb, N. S. (2012). Decreased streamflow in semi-arid basins following drought-induced tree die-off: A counter-intuitive and indirect climate impact on hydrology (vol 406, pg 225, 2011). JOURNAL OF HYDROLOGY, 414, 560-560.
• Heidb??chel, I., Troch, P. A., Lyon, S. W., & Weiler, M. (2012). The master transit time distribution of variable flow systems. Water Resources Research, 48(6).
• Heidbuechel, I., Troch, P. A., Lyon, S. W., & Weiler, M. (2012). The master transit time distribution of variable flow systems. WATER RESOURCES RESEARCH, 48.
• Heidbüchel, I., Troch, P. A., Lyon, S. W., & Weiler, M. (2012). The master transit time distribution of variable flow systems. Water Resources Research, 48(6).
  More info

  Abstract: The transit time of water is an important indicator of catchment functioning and affects many biological and geochemical processes. Water entering a catchment at one point in time is composed of water molecules that will spend different amounts of time in the catchment before exiting. The next water input pulse can exhibit a totally different distribution of transit times. The distribution of water transit times is thus best characterized by a time-variable probability density function. It is often assumed, however, that the variability of the transit time distribution is negligible and that catchments can be characterized with a unique transit time distribution. In many cases this assumption is not valid because of variations in precipitation, evapotranspiration, and catchment water storage and associated (de)activation of dominant flow paths. This paper presents a general method to estimate the time-variable transit time distribution of catchment waters. Application of the method using several years of rainfall-runoff and stable water isotope data yields an ensemble of transit time distributions with different moments. The combined probability density function represents the master transit time distribution and characterizes the intra-annual and interannual variability of catchment storage and flow paths. Comparing the derived master transit time distributions of two research catchments (one humid and one semiarid) reveals differences in dominant hydrologic processes and dynamic water storage behavior, with the semiarid catchment generally reacting slower to precipitation events and containing a lower fraction of preevent water in the immediate hydrologic response. © 2012. American Geophysical Union. All Rights Reserved.
• Oyen, T. V., Suzuki, T., Zijlema, M., Rauwoens, P., & Troch, P. (2012). Modelling the finite amplitude dynamics of tidal sand waves with SWASH. Proceedings of the Coastal Engineering Conference.
• Thompson, S. E., Ngambeki, I., Troch, P. A., Sivapalan, M., & Evangelou, D. (2012). Incorporating student-centered approaches into catchment hydrology teaching: A review and synthesis. Hydrology and Earth System Sciences, 16(9), 3263-3278.
  More info

  Abstract: As hydrologists confront the future of water resources on a globalized, resource-scarce and human-impacted planet, the educational preparation of future generations of water scientists becomes increasingly important. Although hydrology inherits a tradition of teacher-centered direct instruction-. © Author(s) 2012. CC Attribution 3.0 License.
• Zanardo, S., Harman, C. J., Troch, P. A., Rao, P. S., & Sivapalan, M. (2012). Intra-annual rainfall variability control on interannual variability of catchment water balance: A stochastic analysis. Water Resources Research, 48(1).
  More info

  Abstract: We evaluate the extent to which within-year rainfall variability controls interannual variability of catchment water balance. To this end, we analytically derive the probability density function of the annual Budyko evaporation index, B (i.e., the ratio of annual actual evapotranspiration to annual precipitation), by accounting for the stochastic nature of intra-annual rainfall fluctuation and neglecting all other sources of variability. We apply our analytical model to 424 catchments located in different climatic regions across the conterminous United States to perform this assessment. In general, we found that the model is capable of explaining mean B but is less accurate in predicting its coefficient of variation. Nonetheless, in a significant number of catchments the model can provide adequate predictions of the probability density function of B. Clear geographic patterns can be distinguished in the residuals between observed and predicted statistics of B. Interannual variability is thus not always associated with random intra-annual rainfall fluctuations. In some regions, other controls, such as seasonality and vegetation adaptations, are possibly more important. A sensitivity analysis of model parameters helped characterize the dominant controls on the distribution of B in terms of three dimensionless ratios that include climatic and soil characteristics. This study represents the first step in a diagnostic, data-driven analysis of the climatic controls on the interannual variability of catchment water balance. © 2012 by the American Geophysical Union.
• Zanardo, S., Harman, C. J., Troch, P. A., Rao, P., & Sivapalan, M. (2012). Intra-annual rainfall variability control on interannual variability of catchment water balance: A stochastic analysis. Water Resources Research, 48(1).
• Ajami, H., Troch, P. A., Maddock III, T., Meixner, T., & Eastoe, C. (2011). Quantifying mountain block recharge by means of catchment-scale storage-discharge relationships. Water Resources Research, 47(4).
• Ajami, H., Troch, P. A., Maddock, T. I., Meixner, T., & Eastoe, C. (2011). Quantifying mountain block recharge by means of catchment-scale storage-discharge relationships. WATER RESOURCES RESEARCH, 47.
• Brooks, P. D., Troch, P. A., Durcik, M., Gallo, E., & Schlegel, M. (2011). Quantifying regional scale ecosystem response to changes in precipitation: Not all rain is created equal. WATER RESOURCES RESEARCH, 47.
• Brooks, P. D., Troch, P. A., Durcik, M., Gallo, E., & Schlegel, M. (2011). Quantifying regional scale ecosystem response to changes in precipitation: Not all rain is created equal. Water Resources Research, 47(7).
• Carrillo, G., Troch, P. A., Sivapalan, M., Wagener, T., Harman, C., & Sawicz, K. (2011). Catchment classification: Hydrological analysis of catchment behavior through process-based modeling along a climate gradient. Hydrology and Earth System Sciences, 15(11), 3411-3430.
  More info

  Abstract: Catchment classification is an efficient method to synthesize our understanding of how climate variability and catchment characteristics interact to define hydrological response. One way to accomplish catchment classification is to empirically relate climate and catchment characteristics to hydrologic behavior and to quantify the skill of predicting hydrologic response based on the combination of climate and catchment characteristics. Here we present results using an alternative approach that uses our current level of hydrological understanding, expressed in the form of a process-based model, to interrogate how climate and catchment characteristics interact to produce observed hydrologic response. The model uses topographic, geomorphologic, soil and vegetation information at the catchment scale and conditions parameter values using readily available data on precipitation, temperature and streamflow. It is applicable to a wide range of catchments in different climate settings. We have developed a step-by-step procedure to analyze the observed hydrologic response and to assign parameter values related to specific components of the model. We applied this procedure to 12 catchments across a climate gradient east of the Rocky Mountains, USA. We show that the model is capable of reproducing the observed hydrologic behavior measured through hydrologic signatures chosen at different temporal scales. Next, we analyze the dominant time scales of catchment response and their dimensionless ratios with respect to climate and observable landscape features in an attempt to explain hydrologic partitioning. We find that only a limited number of model parameters can be related to observable landscape features. However, several climate-model time scales, and the associated dimensionless numbers, show scaling relationships with respect to the investigated hydrological signatures (runoff coefficient, baseflow index, and slope of the flow duration curve). Moreover, some dimensionless numbers vary systematically across the climate gradient, possibly as a result of systematic co-variation of climate, vegetation and soil related time scales. If such co-variation can be shown to be robust across many catchments along different climate gradients, it opens perspective for model parameterization in ungauged catchments as well as prediction of hydrologic response in a rapidly changing environment. © 2011 Author(s).
• Chorover, J., Troch, P. A., Rasmussen, C., Brooks, P. D., Pelletier, J. D., Breshars, D. D., Huxman, T. E., Kurc, S. A., Lohse, K. A., McIntosh, J. C., Meixner, T., Schaap, M. G., Litvak, M. E., Perdrial, J., Harpold, A., & Durcik, M. (2011). How water, carbon, and energy drive critical zone evolution: The Jemez-Santa Catalina critical zone observatory. Vadose Zone Journal, 10(3), 884-899.
• Chorover, J., Troch, P. A., Rasmussen, C., Brooks, P. D., Pelletier, J. D., Breshears, D. D., Huxman, T. E., Kurc, S. A., Lohse, K. A., McIntosh, J. C., Meixner, T., Schaap, M. G., Litvak, M. E., Perdrial, J., Harpold, A., & Durcik, M. (2011). How Water, Carbon, and Energy Drive Critical Zone Evolution: The Jemez-Santa Catalina Critical Zone Observatory. VADOSE ZONE JOURNAL, 10(3), 884-899.
• Chorover, J., Troch, P. A., Rasmussen, C., Brooks, P. D., Pelletier, J. D., Breshears, D. D., Huxman, T. E., Kurc, S. A., Lohse, K., Mcintosh, J. C., Meixner, T., Schaap, M. G., Litvak, M., Perdrial, J., Harpold, A., & Durcik, M. (2011). How water, carbon, and energy drive critical zone evolution: the Jemez-Santa Catalina Critical Zone Observatory. Vadose Zone Journal, 10, 884-899.
• Doncker, L. D., Troch, P., Verhoeven, R., & Buis, K. (2011). Deriving the relationship among discharge, biomass and Manning's coefficient through a calibration approach. Hydrological Processes, 25(12), 1979-1995.
  More info

  Abstract: The subject of environmental engineering is currently of great interest. Field experiments as well as numerical models have proven their worth in this research field. An introduction to hydrodynamic modelling, coupled to the modelling of vegetation biomass is described. The developed Strive (STream RIVer Ecosystem) model is set up in the Femme ('Flexible Environment for Mathematically Modelling the Environment') environment and has already proven its worth in a large number of calculations (De Doncker et al., 2006, 2008b). Discharges and water levels are modelled together with modelling of electrical conductivity (EC). Extensive measurement campaigns are carried out to collect a large number of observations and calibration of the model is based on this data set. Furthermore, calibration methods and the discussion of this process are displayed. As a result, it is seen that the developed Strive model can model both, hydrodynamic and ecological processes, in an accurate way. The work highlights the importance of detailed determination of Manning's coefficient, dependent on discharge and amount of biomass, as an important calibration parameter for accurate modelling. © 2011 John Wiley & Sons, Ltd.
• Doncker, L. D., Troch, P., Verhoeven, R., Buis, K., & Meire, P. (2011). Validation of the STRIVE model for coupling ecological processes and surface water flow. Journal of Hydroinformatics, 13(4), 741-759.
  More info

  Abstract: The 1D model package STRIVE is verified for simulating the interaction between ecological processes and surface water flow. The model is general and can be adapted and further developed according to the research question. The hydraulic module, based on the Saint-Venant equations, is the core part. The presence of macrophytes influences the water quality and the discharge due to the flow resistance of the river, expressed by Manning's coefficient, and allows an ecological description of the river processes. Based on the advection-dispersion equation, water quality parameters are incorporated and modelled. Calculation of the water quantity parameters, coupled with water quality and inherent validation and sensitivity analysis, is the main goal of this research. An important study area is the River Aa near Poederlee (Belgium), a lowland river with a wealth of vegetation growth, where discharge and vegetation measurements are carried out on a regular basis. The developed STRIVE model shows good and accurate calculation results. The work highlights the possibility of STRIVE to model flow processes, water quality aspects and ecological interaction combined and separately. Coupling of discharges, water levels, amount of biomass and tracer values provides a powerful prediction modelling tool for the ecological behaviour of lowland rivers. © WA Publishing 2011.
• Guardiola-Claramonte, M., Troch, P. A., Breshears, D. D., Huxman, T. E., Switanek, M. B., Durcik, M., & Cobb, N. S. (2011). Decreased streamflow in semi-arid basins following drought-induced tree die-off: A counter-intuitive and indirect climate impact on hydrology. Journal of Hydrology, 406(3-4), 225-233.
  More info

  Abstract: Drought- and infestation-related tree die-off is occurring at regional scales and is projected to increase with global climate change. These large-scale changes in vegetation are expected to influence hydrological responses, but the ecohydrological consequences of die-off have rarely been studied empirically and consequently remain uncertain. Here we evaluate observed hydrologic responses to recent regional-scale die-off of piñon pine (Pinus edulis) in Southwestern USA. Basins with the most tree die-off showed a significant decrease in streamflow over several years following die-off, and this decrease was not attributable to climate variability alone. The results are counterintuitive compared to responses to reductions in tree cover by harvest that have shown an increase in streamflow, although such increases are more substantial for locations with higher precipitation than where the piñon pine die-off occurred. We are unable to isolate the cause of the increase, but note that it is consistent with a reported increase in understory herbaceous cover post-die-off and associated increase in solar radiation reaching near-ground (below the tree canopy overstory), which together would be expected to reduce overland flow. Our study highlights the need to more fully evaluate hydrological responses to drought-induced tree die-off empirically, in addition to modelling studies. More generally, the result illustrate potential indirect effects of climate on hydrological responses mediated through ecohydrological changes in vegetation, which will need to be considered in future water resources assessments. © 2011 Elsevier B.V.
• Guardiola-Clararnonte, M., Troch, P. A., Breshears, D. D., Huxman, T. E., Switanek, M. B., Durcik, M., & Cobb, N. S. (2011). Decreased streamflow in semi-arid basins following drought-induced tree die-off: A counter-intuitive and indirect climate impact on hydrology. JOURNAL OF HYDROLOGY, 406(3-4), 225-233.
• Harman, C. J., Troch, P. A., & Sivapalan, M. (2011). Functional model of water balance variability at the catchment scale: 2. Elasticity of fast and slow runoff components to precipitation change in the continental United States. Water Resources Research, 47(2).
• Lybrand, R., Rasmussen, C., Jardine, A., Troch, P., & Chorover, J. (2011). The effects of climate and landscape position on chemical denudation and mineral transformation in the Santa Catalina mountain critical zone observatory. Applied Geochemistry, 26(SUPPL.), S80-S84.
  More info

  Abstract: Understanding the interactions of climate, physical erosion, chemical weathering and pedogenic processes is essential when considering the evolution of critical zone systems. Interactions among these components are particularly important to predicting how semiarid landscapes will respond to forecasted changes in precipitation and temperature under future climate change. The primary goal of this study was to understand how climate and landscape structure interact to control chemical denudation and mineral transformation across a range of semiarid ecosystems in southern Arizona. The research was conducted along the steep environmental gradient encompassed by the Santa Catalina Mountains Critical Zone Observatory (SCM-CZO). The gradient is dominated by granitic parent materials and spans significant range in both mean annual temperature (>10°C) and precipitation (>50cma-1), with concomitant shift in vegetation communities from desert scrub to mixed conifer forest. Regolith profiles were sampled from divergent and convergent landscape positions in five different ecosystems to quantify how climate-landscape position interactions control regolith development. Regolith development was quantified as depth to paralithic contact and degree of chemical weathering and mineral transformation using a combination of quantitative and semi-quantitative X-ray diffraction (XRD) analyses of bulk soils and specific particle size classes. Depth to paralithic contact was found to increase systematically with elevation for divergent positions at approximately 28cm per 1000m elevation, but varied inconsistently for convergent positions. The relative differences in depth between convergent and divergent landscape positions was greatest at the low and high elevation sites and is hypothesized to be a product of changes in physical erosion rates across the gradient. Quartz/Plagioclase (Q/P) ratios were used as a general proxy for bulk regolith chemical denudation. Q/P was generally higher in divergent landscape positions compared to the adjacent convergent hollows. Convergent landscape positions appear to be collecting solute-rich soil-waters from divergent positions thereby inhibiting chemical denudation. Clay mineral assemblage of the low elevation sites was dominated by smectite and partially dehydrated halloysite whereas vermiculite and kaolinite were predominant in the high elevation sites. The increased depth to paralithic contact, chemical denudation and mineral transformation are likely functions of greater water availability and increased primary productivity. Landscape position within a given ecosystem exerts strong control on chemical denudation as a result of the redistribution of water and solutes across the landscape surface. The combined data from this research demonstrates a strong interactive control of climate, landscape position and erosion on the development of soil and regolith. © 2011 Elsevier Ltd.
• Rasmussen, C., Troch, P. A., Chorover, J., Brooks, P., Pelletier, J., & Huxman, T. E. (2011). An open system framework for integrating critical zone structure and function. BIOGEOCHEMISTRY, 102(1-3), 15-29.
• Rasmussen, C., Troch, P. A., Chorover, J., Brooks, P., Pelletier, J., & Huxman, T. E. (2011). An open system framework for integrating critical zone structure and function. Biogeochemistry, 102(1), 15-29.
• Sawicz, K., Wagener, T., Sivapalan, M., Troch, P. A., & Carrillo, G. (2011). Catchment classification: Empirical analysis of hydrologic similarity based on catchment function in the eastern USA. Hydrology and Earth System Sciences, 15(9), 2895-2911.
  More info

  Abstract: Hydrologic similarity between catchments, derived from similarity in how catchments respond to precipitation input, is the basis for catchment classification, for transferability of information, for generalization of our hydrologic understanding and also for understanding the potential impacts of environmental change. An important question in this context is, how far can widely available hydrologic information (precipitation-temperature-streamflow data and generally available physical descriptors) be used to create a first order grouping of hydrologically similar catchments? We utilize a heterogeneous dataset of 280 catchments located in the Eastern US to understand hydrologic similarity in a 6-dimensional signature space across a region with strong environmental gradients. Signatures are defined as hydrologic response characteristics that provide insight into the hydrologic function of catchments. A Bayesian clustering scheme is used to separate the catchments into 9 homogeneous classes, which enable us to interpret hydrologic similarity with respect to similarity in climatic and landscape attributes across this region. We finally derive several hypotheses regarding controls on individual signatures from the analysis performed here. © 2011 Author(s).
• Sivapalan, M., Yaeger, M. A., Harman, C. J., Xiangyu, X. u., & Troch, P. A. (2011). Functional model of water balance variability at the catchment scale: 1. Evidence of hydrologic similarity and space-time symmetry. Water Resources Research, 47(2).
  More info

  Abstract: This paper presents analysis of annual water balance variability, (1) regional (between-catchment) variability and (2) between-year (interannual) variability and the symmetry between the two. This involved analysis of the annual water balance in terms of a two-stage partitioning, first, of annual precipitation into quick flow and soil wetting and, subsequently, of the resulting soil wetting into slow flow and vaporization. The nature of this water balance partitioning is explored by completing the above analysis in 377 Model Parameter Estimation Experiment (MOPEX) catchments located across the continental United States. We fitted analytical functional relationships to the partitioning at each stage, producing expressions for the three components of quick flow, slow flow, and vaporization. They indicate that the heterogeneity of water balance partitioning among the MOPEX catchments is underlain by a universal relationship that is transferable regionally. Key nondimensional similarity parameters are identified that serve to connect this invariant regional relationship to site-specific response characteristics. These nondimensional formulations are extended to derive analytical expressions for several common metrics of annual water balance. The ability of the functional theory to predict regional patterns of mean annual water balance and interannual variability in individual catchments is assessed. Our analyses show a close symmetry between spatial (regional) variability of mean annual water balances and general trends of temporal (interannual) variability. The suggested functional theory can thus be the basis for data-based assessments of hydrologic similarity and used to assist with predictions of the effects of long-term climate variability and change, through providing a theoretical framework for "space for time" substitutions. Copyright 2011 by the American Geophysical Union.
• Sivapalan, M., Yaeger, M. A., Harman, C. J., Xu, X., & Troch, P. A. (2011). Functional model of water balance variability at the catchment scale: 1. Evidence of hydrologic similarity and space-time symmetry. WATER RESOURCES RESEARCH, 47.
• Sivapalan, M., Yaeger, M. A., Harman, C. J., Xu, X., & Troch, P. A. (2011). Functional model of water balance variability at the catchment scale: 1. Evidence of hydrologic similarity and space-time symmetry. Water Resources Research, 47(2).
• Stratigaki, V., Troch, P., Baelus, L., & Keppens, Y. (2011). Introducing wave regeneration by wind in a mild-slope wave propagation model MILDwave, to investigate the wake effects in the lee of a farm of wave energy converters. Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 5, 429-436.
  More info

  Abstract: The increasing energy demand, the need to reduce greenhouse gas emissions and the shrinking reserves of fossil fuels have all enhanced the interest in sustainable and renewable energy sources, including wave energy. Many concepts for wave power conversion have been invented. In order to extract a considerable amount of wave power, single Wave Energy Converters (abbreviated as WECs) will have to be arranged in arrays or 'farms' using a particular geometrical layout, comprising large numbers of devices. As a result of the interaction between the WECs within a farm, the overall power absorption is affected. In general, the incident waves are partly reflected, transmitted and absorbed by a single WEC. Also, the wave height behind a large farm of WECs is reduced and this reduction may influence neighbouring farms, other users in the sea or even the coastline (wake effects of a WEC farm). The numerical wave propagation model MILDwave has been recently used to study wake effects and energy absorption of farms of WECs, though without taking into account wave regeneration by wind in the lee of the WEC-farm which can be significant in large distances downwave the WECs. In this paper, the implementation of wave growth due to wind in the hyperbolic mild-slope equations of the wave propagation model, MILDwave is described. Several formulations for the energy input from wind found in literature are considered and implemented. The performance of these formulations in MILDwave is investigated and validated. The modified model MILDwave is then applied for the investigation of the influence of the wind on the wakes in the lee of a farm of wave energy converters. Copyright © 2011 by ASME.
• Switanek, M. B., & Troch, P. A. (2011). Decadal prediction of Colorado River streamflow anomalies using ocean-atmosphere teleconnections. GEOPHYSICAL RESEARCH LETTERS, 38.
• Switanek, M. B., & Troch, P. A. (2011). Decadal prediction of Colorado River streamflow anomalies using ocean-atmosphere teleconnections. Geophysical Research Letters, 38(23).
• Thompson, S. E., Harman, C. J., Konings, A. G., Sivapalan, M., Neal, A., & Troch, P. A. (2011). Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater. Water Resources Research, 47(7).
• Thompson, S. E., Harman, C. J., Schumer, R., Wilson, J. S., Basu, N. B., Brooks, P. D., Donner, S. D., Hassan, M. A., Packman, A. I., Rao, P., Troch, P. A., & Sivapalan, M. (2011). Patterns, puzzles and people: Implementing hydrologic synthesis. Hydrological Processes, 25(20), 3256-3266.
• Thompson, S. E., Harman, C. J., Troch, P. A., Brooks, P. D., & Sivapalan, M. (2011). Spatial scale dependence of ecohydrologically mediated water balance partitioning: A synthesis framework for catchment ecohydrology. WATER RESOURCES RESEARCH, 47.
• Thompson, S. E., Harman, C. J., Troch, P. A., Brooks, P. D., & Sivapalan, M. (2011). Spatial scale dependence of ecohydrologically mediated water balance partitioning: A synthesis framework for catchment ecohydrology. Water Resources Research, 47(5).
• Victor, L., Troch, P., & Kofoed, J. P. (2011). On the effects of geometry control on the performance of overtopping wave energy converters. Energies, 4(10), 1574-1600.
  More info

  Abstract: Overtopping wave energy converters (OWECs) are designed to extract energy from ocean waves based on wave overtopping into a reservoir, which is emptied into the ocean through a set of low-head turbines, and typically feature a low crest freeboard and a smooth impermeable steep slope. In the process of optimizing the performance of OWECs, the question arises whether adapting the slope geometry to the variable wave characteristics at the deployment site (i.e., geometry control) can increase the overall hydraulic efficiency and overall hydraulic power compared to a fixed slope geometry. The effect of five different geometry control scenarios on the overall hydraulic efficiency and overall hydraulic power of OWECs has been simulated for three possible deployment sites using empirical prediction formulae. The results show that the effect of an adaptive slope angle is relatively small. On the other hand, adapting the crest freeboard of the OWECs to the wave characteristics increases the overall hydraulic efficiency and power. Based on the simulations, gains in overall hydraulic power of at least 30% are achievable when applying an adaptive crest freeboard compared to a fixed crest freeboard.
• Victor, L., Troch, P., & Kofoed, J. P. (2011). Optimization of overtopping wave energy converters by geometry control. Proceedings of the International Offshore and Polar Engineering Conference, 606-613.
  More info

  Abstract: In this paper, the results of a study on the effects of geometry control on the performance of overtopping wave energy converters with a simple geometry built in coastal structures (simple OWECs) are presented. Empirical formulae, derived based on experimental tests on simple OWECs with varying geometry, are applied to a number of test cases. It appears that adapting the slope angle and crest freeboard of a simple OWEC to the sea states at a specific nearshore location, can result in significant increases in obtained hydraulic power. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).
• Voepel, H., Ruddell, B., Schumer, R., Troch, P. A., Brooks, P. D., Neal, A., Durcik, M., & Sivapalan, M. (2011). Quantifying the role of climate and landscape characteristics on hydrologic partitioning and vegetation response. WATER RESOURCES RESEARCH, 47.
• Voepel, H., Ruddell, B., Schumer, R., Troch, P. A., Brooks, P. D., Neal, A., Durcik, M., & Sivapalan, M. (2011). Quantifying the role of climate and landscape characteristics on hydrologic partitioning and vegetation response. Water Resources Research, 47(8).
• Vos, L. D., Rouck, J. D., Troch, P., & Frigaard, P. (2011). Empirical design of scour protections around monopile foundations. Part 1: Static approach.. Coastal Engineering, 58(6), 540-553.
  More info

  Abstract: Together with new opportunities, offshore wind farms raise new engineering challenges. An important aspect relates to the erosion of bottom material around the foundation of the wind turbines, caused by the local increase of the wave and current induced flow velocities by the pile's presence. Typically, the expected scour has a considerable impact on the stability and dynamic behavior of the wind turbine and a scour protection is placed to avoid erosion of the soil close to the foundation. Although much experience exists on the design of scour protections around bridge piers (which are placed in a current alone situation), at present, little design guidelines exist for the specific case of a scour protection around a monopile foundation subjected to a combined wave and current loading. This paper describes the derivation of a static design formula to calculate the required stone size for a scour protection around a monopile foundation in a combined wave and current climate. Due to the difficult physical processes involved in flow disturbance and displacement of bed protection material at the base of a foundation, the formula is based on the results of an experimental model study which is described in this paper. A linear relationship was found between the critical bed shear-stress Tcr and the bed shear-stress caused by current Tc and waves Tw, respectively. When applying the formula for a typical situation in the North Sea, a significant reduction of the required stone size is obtained, compared to existing design criteria.In part 2, following this paper (De Vos et al., in preparation), an optimization of the design procedure is obtained by allowing limited stone motion for top layer stones. This is obtained by adding a damage factor to the design formula, which leads to significantly smaller stone diameters and thus a more economical approach. © 2011 Elsevier B.V.
• Beels, C., Troch, P., Backer, G. D., Vantorre, M., & Rouck, J. D. (2010). Numerical implementation and sensitivity analysis of a wave energy converter in a time-dependent mild-slope equation model. Coastal Engineering, 57(5), 471-492.
  More info

  Abstract: Several Wave Energy Converters (abbreviated as WECs) have intensively been studied and developed during the last decade and currently small farms of WECs are getting installed. WECs in a farm are partly absorbing, partly redistributing the incident wave power. Consequently, the power absorption of each individual WEC in a farm is affected by its neighbouring WECs. The knowledge of the wave climate around the WEC is needed to predict its performance in the farm. In this paper a technique is developed to implement a single and multiple WECs based on the overtopping principle in a time-dependent mild-slope equation model. So far, the mild-slope equations have been widely used to study wave transformations around coastal and offshore structures, such as breakwaters, piles of windmills and offshore platforms. First the limitations of the WEC implementation are discussed through a sensitivity analysis. Next the developed approach is applied to study the wave height reduction behind a single WEC and a farm. The wake behind an isolated WEC is investigated for uni- and multidirectional waves; it is observed that an increase of the directional spread leads to a faster wave redistribution behind the WEC. Further the wake in the lee of multiple WECs is calculated for two different farm lay-outs, i.e. an aligned grid and a staggered grid, by adapting the performance of each WEC to its incident wave power. The evolved technique is a fast tool to find the optimal lay-out of WECs in a farm and to study the possible influence on surrounding activities in the sea. © 2010 Elsevier B.V.
• Beels, C., Troch, P., Visch, K. D., Kofoed, J. P., & Backer, G. D. (2010). Application of the time-dependent mild-slope equations for the simulation of wake effects in the lee of a farm of Wave Dragon wave energy converters. Renewable Energy, 35(8), 1644-1661.
  More info

  Abstract: Time-dependent mild-slope equations have been extensively used to compute wave transformations near coastal and offshore structures for more than 20 years. Recently the wave absorption characteristics of a Wave Energy Converter (abbreviated as WEC) of the overtopping type have been implemented in a time-dependent mild-slope equation model by using numerical sponge layers. In this paper the developed WEC implementation is applied to a single Wave Dragon WEC and multiple Wave Dragon WECs. The Wave Dragon WEC is a floating offshore converter of the overtopping type. Two wave reflectors focus the incident wave power towards a ramp. The focussed waves run up the ramp and overtop in a water reservoir above mean sea level. The obtained potential energy is converted into electricity when the stored water drains back to the sea through hydro turbines. The wave reflectors and the main body (ramp and reservoir) are simulated as porous structures, exhibiting the same reflection, respectively absorption characteristics as obtained for the prototype Wave Dragon WEC. The wake effects behind a single Wave Dragon WEC are studied in detail for uni- and multidirectional waves. The shadow zone indicating the wake effect is decreasing with increasing directional spreading. The wake in the lee of a farm of five Wave Dragon WECs, installed in a staggered grid (3 WECs in the first row and 2 WECs in the second row), is calculated for three in-between distances of respectively D, 2D and 3D, with D the distance between the tips of the wave reflectors of a single WEC. As a result, a farm of five Wave Dragon WECs installed in a staggered grid with an in-between distance of 2D is preferred, when taking cost and spatial considerations into account. © 2009 Elsevier Ltd. All rights reserved.
• Guardiola-Claramonte, M., Fox, J. M., Giambelluca, T. W., & Troch, P. A. (2010). Changing land use in the Golden Triangle: Where the rubber meets the road. Sustainability Science for Watershed Landscapes, 235-250.
  More info

  Abstract: Land use and land cover change in Montane Mainland Southeast Asia (MMSEA) ischanging dramatically as shifting cultivation gives way to commercial agriculture driven bydomestic demand and regional trade agreements. In Xishuangbanna, China, both owners ofsemi-privatised state farms and minority farmers are planting rubber at rates that threatento transform landscapes, with elevations of between 300 m and even above 1,000 m, intoan unbroken carpet of rubber. While it has become apparent that this region is on thecusp of major changes in tree cover, there is much uncertainty about the direction of changeand the sustainability of this land use in terms of people's livelihoods and environmentalvariables such as biodiversity, carbon sequestration, watershed hydrolog y, and climate.This paper explores the hydrological sustainability of this land-cover change at thebasin scale, showing the importance of science for a sustainable water resources managementpolicy. Observations in the study basin showed that water is an important and neededresource of rubber especially during the driest and hottest season. These results were notobserved in native vegetation. This could also have negative large-scale implications onavailable local and regional water resources that need to be considered before launching land management policies. © 2010 Institute of Southeast Asian Studies, Singapore. All rights reserved.
• Guardiola-Claramonte, M., Troch, P. A., Ziegler, A. D., Giambelluca, T. W., Durcik, M., Vogler, J. B., & Nullet, M. A. (2010). Hydrologic effects of the expansion of rubber (Hevea brasiliensis) in a tropical catchment. ECOHYDROLOGY, 3(3), 306-314.
• Guardiola-Claramonte, M., Troch, P. A., Ziegler, A. D., Giambelluca, T. W., Durcik, M., Vogler, J. B., & Nullet, M. A. (2010). Hydrologic effects of the expansion of rubber (Hevea brasiliensis) in a tropical catchment. Ecohydrology, 3(3), 306-314.
  More info

  Abstract: This study investigates basin-scale hydrologic implications of the replacement of forest-dominated land cover by rubber plantations in Montane Mainland Southeast Asia. The paper presents a new method for estimating the water demand of rubber and consequently water losses to the atmosphere through rubber evapotranspiration (ET). In this paper we argue that rubber ET is energy-limited during the wet season, but during the dry season water consumption is mostly governed by environmental variables that directly affect rubber phenology, namely, vapour pressure deficit, temperature and photoperiodicity. The proposed ET model is introduced into a hillslope-based hydrologic model to predict the basin-scale hydrologic consequences of rubber replacing native vegetation. Simulations suggest greater annual catchment water losses through ET from rubber dominated landscapes compared to traditional vegetation cover. This additional water use reduces discharge from the basin, or its storage. © 2010 John Wiley & Sons, Ltd.
• Harpold, A. A., Lyon, S. W., Troch, P. A., & Steenhuis, T. S. (2010). The Hydrological Effects of Lateral Preferential Flow Paths in a Glaciated Watershed in the Northeastern USA. VADOSE ZONE JOURNAL, 9(2), 397-414.
• Harpold, A. A., Lyon, S. W., Troch, P. A., & Steenhuis, T. S. (2010). The hydrological effects of lateral preferential flow paths in a glaciated watershed in the northeastern USA. Vadose Zone Journal, 9(2), 397-414.
  More info

  Abstract: Despite observational evidence of lateral preferential flow paths in northeastern U.S. watersheds, their effects on the sources of runoff remain unclear. An intense field survey was undertaken during the 2007 growing season to determine the sources of stream runoff from a 2.51 km2 watershed in the Catskill Mountains, New York State. Lateral preferential flow paths are caused by groundwater springs and soil piping in this region. A two-component hydrograph separation using δ18O showed that event water (rain water) was a significant source of runoff during nine rainfall events (from July to October). With these rainfall events, 14 to 37% of the volume and 18 to 49% of the peak streamflow was attributable to event water. Further, end-member mixing analysis (EMMA), using δ18O, Si, and dissolved organic carbon (DOC), showed that saturated areas accounted for 2 to 24% of the total volume and 4 to 59% of peak streamflow but that groundwater was the dominant source of runoff volume during all events. Field surveys of saturated areas also suggested that near-stream areas were insufficient to generate the observed stream chemistry during rainfall events larger than 8 mm. A connection with the hillside saturated areas was therefore required to explain the results of the hydrograph separations, which were corroborated by the timing of the transient (perched) groundwater and overland flow. The hydrometric measurements confirmed that hillside lateral preferential flow paths rapidly transported water to near-stream saturation areas during runoff events under relatively dry antecedent conditions. A qualitative comparison with conventional techniques for distributing variable saturation areas (VSA) using surface topography and soil transmissivity (i.e., topographic index and soil topographic index), which do not consider the effects of lateral preferential flow paths, demonstrated that typical parameterizations (on the order of
• Hurkmans, R., Terink, W., Uijlenhoet, R., Torfs, P., Jacob, D., & Troch, P. A. (2010). Changes in Streamflow Dynamics in the Rhine Basin under Three High-Resolution Regional Climate Scenarios. JOURNAL OF CLIMATE, 23(3), 679-699.
• Hurkmans, R., Terink, W., Uijlenhoet, R., Torfs, P., Jacob, D., & Troch, P. A. (2010). Changes in streamflow dynamics in the Rhine basin under three high-resolution regional climate scenarios. Journal of Climate, 23(3), 679-699.
  More info

  Abstract: Because of global warming, the hydrologic behavior of the Rhine basin is expected to shift from a combined snowmelt-and rainfall-driven regime to a more rainfall-dominated regime. Previous impact assessments have indicated that this leads, on average, to increasing streamflow by ~30% in winter and spring and decreasing streamflow by a similar value in summer. In this study, high-resolution (0.088°) regional climate scenarios conducted with the regional climate model REMO (REgional MOdel) for the Rhine basin are used to force a macroscale hydrological model. These climate scenarios are based on model output from the ECHAM5-Max Planck Institute Ocean Model (MPI-OM) global climate model, which is in turn forced by three Special Report on Emissions Scenarios (SRES) emission scenarios: A2, A1B, and B1. The Variable Infiltration Capacity model (VIC; version 4.0.5) is used to examine changes in streamflow at various locations throughout the Rhine basin. Average streamflow, peak flows, low flows, and several water balance terms are evaluated for both the first and second half of the twenty-first century. The results reveal a distinct contrast between those periods. The first half is dominated by increased precipitation, causing increased streamflow throughout the year. During the second half of the century, a streamflow increase in winter/spring and a decrease in summer is found, similar to previous studies. This is caused by 1) temperature and evapotranspiration, which are considerably higher during the second half of the century; 2) decreased precipitation in summer; and 3) an earlier start of the snowmelt season. Magnitudes of peak flows increase during both periods, and the magnitudes of streamflow droughts increase only during the second half of the century. © 2010 American Meteorological Society.
• Ivanov, V. Y., Fatichi, S., Jenerette, G. D., Espeleta, J. F., Troch, P. A., & Huxman, T. E. (2010). Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation. WATER RESOURCES RESEARCH, 46.
• Ivanov, V. Y., Fatichi, S., Jenerette, G. D., Espeleta, J. F., Troch, P. A., & Huxman, T. E. (2010). Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation. Water Resources Research, 46(9).
• Kisacik, D., Troch, P., & Bogaert, P. V. (2010). Experimental results of breaking wave impact on a vertical wall with an overhanging horizontal cantilever slab. Proceedings of the Coastal Engineering Conference.
  More info

  Abstract: Physical experiments (at a scale of 1/20) are carried out using a vertical wall with horizontal cantilevering slab. Tests are conducted for a range of values of water depth, wave period and wave height. A parametric analysis of measured forces (F h and F v) both on the vertical and horizontal part of the scaled model respectively is conducted. The highest impact pressure and forces are measured in the case of breaking waves with a small air trap. Maximum pressures are measured around SWL and at the corner of the scaled model. The horizontal part of the scaled model is more exposed to impact waves than the vertical part. F h and F v are very sensitive for the variation of water depth (h s) and wave height (H) while variation of wave period (T) has a rather limited effect.
• Kisacik, D., Verleysen, P., Bogaert, P. V., & Troch, P. (2010). Comparative study on breaking wave forces on vertical walls with cantilever surfaces. Proceedings of the International Offshore and Polar Engineering Conference, 3, 888-894.
  More info

  Abstract: Physical experiments (at a scale of 1/20) are carried out using two different models: a vertical wall with cantilevering slab and a simple vertical wall. Tests are conducted for a range of values of water depth, wave period and wave height. The largest peak pressures were recorded at the SWL (82 * ρghs) on the vertical part and at the fixed corner of the cantilever slab (90 * ρghs). Pressure measurements and derived force calculations on the simple vertical wall were used to evaluate the existing prediction formulas. A significant effect of the cantilevering part is observed on the total horizontal force and overturning moment of a simple vertical wall. This is due to secondary impact occurring on the overhanging part by a jet climbing on the vertical part. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE).
• Lyon, S. W., & Troch, P. A. (2010). Development and application of a catchment similarity index for subsurface flow. WATER RESOURCES RESEARCH, 46.
• Lyon, S. W., & Troch, P. A. (2010). Development and application of a catchment similarity index for subsurface flow. Water Resources Research, 46(3).
• McDonnell, J. J., McGuire, K., Aggarwal, P., Beven, K. J., Biondi, D., Destouni, G., Dunn, S., James, A., Kirchner, J., Kraft, P., Lyon, S., Maloszewski, P., Newman, B., Pfister, L., Rinaldo, A., Rodhe, A., Sayama, T., Seibert, J., Solomon, K., , Soulsby, C., et al. (2010). How old is streamwater? Open questions in catchment transit time conceptualization, modelling and analysis. Hydrological Processes, 24(12), 1745-1754.
• Meire, D., Doncker, L. D., Declercq, F., Buis, K., Troch, P., & Verhoeven, R. (2010). Modelling river-floodplain interaction during flood propagation. Natural Hazards, 55(1), 111-121.
  More info

  Abstract: The (re)integration of flood storage areas in the river system is considered and proved as an effective flood protection measure. By their (controlled) filling and emptying, inundation risks for downstream areas with higher vulnerability can be reduced. They have an influence not only on the flood level, but also on the residence time of the water in the river ecosystem, which is an important biological parameter. A good prediction of storage flow is therefore necessary in an integrated ecosystem model. In such a model, which is being developed by the universities of Ghent and Antwerp, hydraulic, biological and biogeochemical processes are coupled. In this paper, a one-dimensional hydrodynamic module of the integrated STRIVE (STReam RIVer Ecosystem) model, which is based on the de Saint-Venant equations and solved by the Preissmann scheme, is adapted to be able to include flow exchange with storage cells. This model is validated with experimental laboratory measurements on a small scale. The flow between the storage cells and the river is controlled by weirs (flooded river banks). Model simulations with STRIVE are also compared with HEC-RAS simulations. Good agreement between simulations of both models and between the STRIVE simulations and the measurements is found. © 2010 Springer Science+Business Media B.V.
• Pauwels, V., & Troch, P. A. (2010). Estimation of aquifer lower layer hydraulic conductivity values through base flow hydrograph rising limb analysis. WATER RESOURCES RESEARCH, 46.
• Pauwels, V., & Troch, P. A. (2010). Estimation of aquifer lower layer hydraulic conductivity values through base flow hydrograph rising limb analysis. Water Resources Research, 46(3).
• R., V., & Troch, P. A. (2010). Estimation of aquifer lower layer hydraulic conductivity values through base flow hydrograph rising limb analysis. Water Resources Research, 46(3).
  More info

  Abstract: The estimation of catchment-averaged aquifer hydraulic conductivity values is usually performed through a base flow recession analysis. Relationships between the first time derivatives of the base flow and the base flow values themselves, derived for small and large values of time, are used for this purpose. However, in the derivation of the short-time equations, an initially fully saturated aquifer without recharge with sudden drawdown is assumed, which occurs very rarely in reality. It is demonstrated that this approach leads to a nonnegligible error in the parameter estimates. A new relationship is derived, valid for the rising limb of a base flow hydrograph, succeeding a long rainless period. Application of this equation leads to accurate estimates of the aquifer lower layer saturated hydraulic conductivity. Further, it has been shown analytically that, if base flow is modeled using the linearized Boussinesq equation, the base flow depends on the effective aquifer depth and the ratio of the saturated hydraulic conductivity to the drainable porosity, not on these three parameters separately. The results of the new short-time expression are consistent with this finding, as opposed to the use of a traditional base flow recession analysis. When base flow is modeled using the nonlinear Boussinesq equation, the new expression can be used, without a second equation for large values of time, to estimate the aquifer lower layer hydraulic conductivity. Overall, the results in this paper suggest that the new methodology outperforms a traditional recession analysis for the estimation of catchment-averaged aquifer hydraulic conductivities. Copyright 2010 by the American Geophysical Union.
• Stratigaki, V., Vanneste, D., Troch, P., Gysens, S., & Willems, M. (2010). Numerical modeling of wave penetration in Ostend harbour. Proceedings of the Coastal Engineering Conference.
  More info

  Abstract: The initial Ostend harbour entrance at the North Sea coast of Belgium is being modified and extended with two new rubble-mound breakwaters. Through an integrated study of the wave penetration in Ostend harbour, the waves are being acquired by prototype measurements and physical and numerical modelling is carried out. Two numerical models are used. SimWave is a numerical model based on Nwogu's extended Boussinesq equations. The second numerical model is MILDwave, a mild-slope wave propagation model based on the equations of Radder and Dingemans. The present study concentrates on applications of the numerical models, throughout the different design stages and construction phases of the new breakwaters.
• Tichko, S., Van, J., Vanmassenhove, N., Schutter, G. D., Vierendeels, J., Verhoeven, R., & Troch, P. (2010). Numerical modelling of the filling of formworks with self-compacting concrete. WIT Transactions on Engineering Sciences, 69, 157-168.
  More info

  Abstract: This paper describes the numerical modelling of the flow of self-compacting concrete (SCC) in column and wall formworks during the filling process. It is subdivided into four main parts. In the first part, the rheological properties of SCC and the theory regarding the pressure exerted by the SCC on the formworks are shortly described. In the second part, the formwork filling tests, which have been carried out at the Magnel Laboratory for Concrete Research of the Ghent University, are presented. The general layout of the tests and the measurement set-up are clearly described. In the third part, the numerical modelling of the flow of SCC using a commercially available solver is explained as well as the obtained results from the CFD simulations. Finally in the last part, a comparison is made between the measurements and the simulation results. The formwork pressures are hydrostatic for SCC pumped from the base of the formworks. © 2010 WIT Press.
• Troch, P., Beels, C., Rouck, J. D., & Backer, G. D. (2010). Wake effects behind a farm of wave energy converters for irregular long-crested and short-crested waves. Proceedings of the Coastal Engineering Conference.
  More info

  Abstract: The contribution of wave energy to the renewable energy supply is rising. To extract a considerable amount of wave power, Wave Energy Converters (WECs) are arranged in several rows or in a 'farm'. WECs in a farm are interacting (e.g. the presence of other WECs influence the operational behaviour of a single WEC) and the overall power absorption is affected. In this paper wake effects in the lee of a single WEC and multiple WECs of the overtopping type, where the water volume of overtopped waves is first captured in a basin above mean sea level and then drains back to the sea through hydro turbines, are studied using the time-dependent mild-slope equation model MILDwave. The wake behind a single WEC is investigated for long-crested and short-crested incident waves. The wake becomes wider for larger wave peak periods. An increasing directional spreading results in a faster wave regeneration and a shorter wake behind the WEC. The wake in the lee of multiple WECs is calculated for two different farm lay-outs, i.e. an aligned grid and a staggered grid, with varying lateral and longitudinal spacing. The wave power redistribution in and behind each farm lay-out is studied in detail using MILDwave. In general, the staggered grid results in the highest overall wave power absorption.
• Vanlishout, V., Verhagen, H. J., & Troch, P. (2010). Oblique wave transmission through rough impermeable rubble mound submerged breawaters. Proceedings of the Coastal Engineering Conference.
  More info

  Abstract: There is a growing interest in the application of submerged rubble mound breakwaters as coastal defence structures. As their defensive ability highly depends on the amount of wave energy remaining at their lee side, the accurate prediction of the energy in the lee of such structures is of utmost importance. Past experiments have shown that the behaviour of rough permeable rubble mound structures under oblique wave attack was found to be significantly different from that of smooth impermeable low crested structures. This behavioural difference has led to the research objective of this present study which is to investigate oblique wave transmission by rough impermeable rubble mound submerged breakwaters using 3D physical model tests. This study intentionally uncouples two parameters, being the permeability of the core and the roughness of the breakwater. Analysing the data of this study shows that the permeability of the core has no visible influence on the structure's behaviour with respect to the influence of oblique wave attack. The fully permeable rough rubble mound breakwater behaves analogous to the fully impermeable rough rubble mound breakwater.
• Vanneste, D., & Troch, P. (2010). Experimental research on pore pressure attenuation in rubble-mound breakwaters. Proceedings of the Coastal Engineering Conference.
  More info

  Abstract: The paper describes the pore pressure measurements in a small scale breakwater model performed at Ghent University, Belgium. Two phenomena related to the pore pressure distribution within the breakwater are discussed: the amount of energy dissipation through the armour and filter layer (represented by the 'reference pressure') and the exponential pore pressure attenuation inside the core of the breakwater. The test results are compared with results from literature and with the empirical damping model presented by Burcharth et al. (1999) and Troch (2000). Magnitudes of the reference pressures are found to be strongly dependent on the wave steepness. The pore pressure attenuation obtained from the present experiments shows to be in accordance with the empirical damping model. A suggestion is made for a better prediction of the damping coefficient by eliminating the influence of the wave height in the empirical damping model.
• Victor, L., Kofoed, J. P., & Troch, P. (2010). Hydrodynamic behavior of overtopping wave energy converters built in sea defense structures. Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 3, 405-414.
  More info

  Abstract: Many sea defense structures need to be adapted to the rising sea water level and changing wave climate due to global warming. The accordingly required investments open perspectives for wave energy converters (WECs) - that are built as part of the sea defense structures - to become economically viable. In this paper the average overtopping discharges q of overtopping wave energy converters built in sea defense structures are studied. Physical model tests with this type of devices have been carried out in a wave flume leading to experimentally determined values for the average overtopping discharge q. These experimental data are compared with predicted average overtopping discharges using existing empirical formulae from literature - derived mainly for sea defense structures. Overtopping WECs have small relative crest freeboard heights and smooth slopes to maximize overtopping, which is contradictive to the basic role of sea defense structures. As a consequence, the experimentally achieved average overtopping discharges are situated in a range that is not well covered by the existing traditional prediction formulae. The presented results for linear-slope overtopping WECs fill the gap between those for smooth dikes and those for plain vertical walls. The overtopping behavior in that particular range is discussed in this paper. Copyright © 2010 by ASME.
• Volkmann, T., Lyon, S. W., Gupta, H. V., & Troch, P. A. (2010). Multicriteria design of rain gauge networks for flash flood prediction in semiarid catchments with complex terrain. WATER RESOURCES RESEARCH, 46.
• Volkmann, T., Lyon, S. W., Gupta, H. V., & Troch, P. A. (2010). Multicriteria design of rain gauge networks for flash flood prediction in semiarid catchments with complex terrain. Water Resources Research, 46(11).
• Wagener, T., Sivapalan, M., Troch, P. A., McGlynn, B. L., Harman, C. J., Gupta, H. V., Kumar, P., Rao, P., Basu, N. B., & Wilson, J. S. (2010). The future of hydrology: An evolving science for a changing world. WATER RESOURCES RESEARCH, 46.
• Wagener, T., Sivapalan, M., Troch, P. A., McGlynn, B. L., Harman, C. J., Gupta, H. V., Kumar, P., Rao, P., Basu, N. B., & Wilson, J. S. (2010). The future of hydrology: An evolving science for a changing world. Water Resources Research, 46(5).
• Adams, H. D., Guardiola-Claramonte, M. .., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Leuzinger et al.: Drought-induced tree mortality temperature sensitivity requires pressing forward with best available science. Proceedings of the National Academy of Sciences of the United States of America, 106(38).
• Adams, H. D., Guardiola-Claramonte, M. .., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Sala: Temperature sensitivity in drought-induced tree mortality hastens the need to further resolve a physiological model of death. Proceedings of the National Academy of Sciences of the United States of America, 106(26).
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Camilo, V. J., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Leuzinger et al.: Drought-induced tree mortality temperature sensitivity requires pressing forward with best available science. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(38), E107-E107.
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Leuzinger et al.: Drought-induced tree mortality temperature sensitivity requires pressing forward with best available science. Proceedings of the National Academy of Sciences of the United States of America, 106(38), E107.
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Sala: Temperature sensitivity in drought-induced tree mortality hastens the need to further resolve a physiological model of death. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(26), E69-E69.
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Reply to Sala: Temperature sensitivity in drought-induced tree mortality hastens the need to further resolve a physiological model of death. Proceedings of the National Academy of Sciences of the United States of America, 106(26), E69.
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(17), 7063-7066.
• Adams, H. D., Guardiola-Claramonte, M., Barron-Gafford, G. A., Villegas, J. C., Breshears, D. D., Zou, C. B., Troch, P. A., & Huxman, T. E. (2009). Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought. Proceedings of the National Academy of Sciences of the United States of America, 106(17), 7063-7066.
  More info

  PMID: 19365070;PMCID: PMC2678423;Abstract: Large-scale biogeographical shifts in vegetation are predicted in response to the altered precipitation and temperature regimes associated with global climate change. Vegetation shifts have profound ecological impacts and are an important climate-ecosystem feedback through their alteration of carbon, water, and energy exchanges of the land surface. Of particular concern is the potential for warmer temperatures to compound the effects of increasingly severe droughts by triggering widespread vegetation shifts via woody plant mortality. The sensitivity of tree mortality to temperature is dependent on which of 2 non-mutually-exclusive mechanisms predominates - temperature-sensitive carbon starvation in response to a period of protracted water stress or temperature-insensitive sudden hydraulic failure under extreme water stress (cavitation). Here we show that experimentally induced warmer temperatures (≈4 °C) shortened the time to drought-induced mortality in Pinus edulis (pinon shortened pine) trees by nearly a third, with temperature-dependent differences in cumulative respiration costs implicating carbon starvation as the primary mechanism of mortality. Extrapolating this temperature effect to the historic frequency of water deficit in the southwestern United States predicts a 5-fold increase in the frequency of regional-scale tree die-off events for this species due to temperature alone. Projected increases in drought frequency due to changes in precipitation and increases in stress from biotic agents (e.g., bark beetles) would further exacerbate mortality. Our results demonstrate the mechanism by which warmer temperatures have exacerbated recent regional die-off events and background mortality rates. Because of pervasive projected increases in temperature, our results portend widespread increases in the extent and frequency of vegetation die-off.
• Adhikari, B., Verhoeven, R., & Troch, P. (2009). Appropriate rehabilitation strategy for a traditional irrigation supply system: A case from the Babai area in Nepal. Water Science and Technology, 60(11), 2819-2828.
  More info

  PMID: 19934503;Abstract: This paper studies primary canals of three traditional irrigation systems in the southern plains of Nepal. It offers a scientific interpretation of the indigenous technology applied to the systems, which facilitates to use the same channel network for irrigation, drainage and flood management. The flood management technology of the farmers by diverting as much discharge as possible to the field channels results in the reduction of discharge towards the downstream part of the main channel. It is depicted in the simulation study that uses the river analysis program HEC-RAS 4.0. A cascade of weirs is found to be the most cost effective and user-friendly option to upgrade these systems preserving the existing irrigation, drainage as well as flood management functions. This study suggests that the conventional irrigation design principles should be applied very cautiously with full knowledge of the existing socio-institutional setting, hydro-ecological regime and indigenous technology for upgrading any traditional irrigation system successfully. The indigenous flood management technology strengthens the emerging concept that the floods in the Ganges plain are to be managed, not controlled. © IWA Publishing 2009.
• Adhikari, B., Verhoeven, R., & Troch, P. (2009). Fair and sustainable irrigation water management in the Babai basin, Nepal. Water Science and Technology, 59(8), 1505-1513.
  More info

  PMID: 19403963;Abstract: This paper attempts to find a strategy to provide year-round irrigation for cultivating three crops per year in the southern plains of the country taking a case study of the Babai basin. Despite having enough flows during the summer for growing rice in total 27,000 ha area, the dry season flows of the Babai river can irrigate only 6,300 ha in winter and 4,000 ha in spring limiting the cropping intensity to 138.50%. It is proposed to irrigate the 7,500 ha southern dry area at the right bank bringing water from a large snow-fed river: the Karnali. water balance study of the three irrigation regions to be irrigated from the Babai source preserving their existing water rights showed that the year-round irrigation at the west with the proposed arrangement will fall short of only 13.9 million m3 water volume. At the east side, the head reach area and the tail portion will fall short of 19.4 and 66.4 million m 3 of water to insure a cropping intensity of 250%. The deficits can be fulfilled by means of capturing the excess river water of rainy season in local reservoirs and by making conjunctive use of groundwater. The proposed solution is financially, environmentally and socially viable being a cost effective, user friendly and should be the linchpin towards attaining a sustainable year-round irrigation in the region. © IWA Publishing 2009.
• Adhikari, B., Verhoeven, R., & Troch, P. (2009). Inter-basin transfer of Nepal's water resources for sustainable benefits. Water and Urban Development Paradigms: Towards an Integration of Engineering, Design and Management Approaches - Proceedings of the International Urban Water Conference, 647-653.
  More info

  Abstract: This article suggests that the east-west transfer of water from larger rivers in Nepal by tunnelling through the last hill in three places is an appropriate alternative to high dams. Dams are unsuitable for a highly earthquake prone area, such as Nepal, and they cannot cope with ever increasing sediment loads of the Himalayan Rivers. Nepal must maximize irrigation in its Terai using the Himalayan river water for maintaining food security in the country. India is moving forward towards large-scale plans to transfer water from the eastern to western rivers, for which Nepal's foot hill can serve as the best place to transfer solely from the gravity. This study suggests storing water in local reservoirs and groundwater aquifer in the Ganges plain, which would secure dry season irrigation, as well as increase Ganges River flows to benefit Bangladesh. The solution has no fixed life span like dams, and hence deserves potentials to serve for unlimited time in a sustainable manner. © 2009 Taylor & Francis Group.
• Adhikari, B., Verhoeven, R., & Troch, P. (2009). Water rights of the head reach farmers in view of a water supply scenario at the extension area of the Babai Irrigation Project, Nepal. Physics and Chemistry of the Earth, 34(1-2), 99-106.
  More info

  Abstract: The farmer managed irrigation systems (FMIS) represent those systems which are constructed and operated solely by the farmers applying their indigenous technology. The FMIS generally outperform the modern irrigation systems constructed and operated by the government agencies with regard to the water delivery effectiveness, agricultural productivity etc., and the presence of a sound organization responsible to run the FMIS, often referred to as the 'social capital', is the key to this success. This paper studies another important aspect residing in the FMIS: potentials to expand the irrigation area by means of their proper rehabilitation and modernization. Taking the case study of the Babai Irrigation Project in Nepal, it is demonstrated that the flow, which in the past was used to irrigate the 5400 ha area covered by three FMIS, can provide irrigation to an additional 8100 ha in the summer, 4180 ha vegetables in the winter and 1100 ha maize in the spring season after the FMIS rehabilitation. The "priority water rights" of the FMIS part have been evaluated based on relevant crop water requirement calculations and is found to be equal to 85.4 million m3 per year. Consequently, the dry season irrigation strategy at the extension area could be worked out based on the remaining flow. By storing the surplus discharge of the monsoon and autumn in local ponds, and by consuming them in dry period combined with nominal partial irrigation practice, wheat and mustard can be cultivated over about 4000 ha of the extension area. Furthermore, storage and surface irrigation both contribute to the groundwater recharge. The conjunctive use of ground, surface and harvested water might be the mainstream in the future for a sustainable irrigation water management in the region. © 2008 Elsevier Ltd. All rights reserved.
• Beels, C., Troch, P., Rouck, J. D., Versluys, T., & Backer, G. D. (2009). Numerical simulation of wake effects in the lee of a farm of wave energy converters. Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 4(PART B), 961-971.
  More info

  Abstract: The contribution of wave energy to the renewable energy supply is rising. To extract a considerable amount of wave power, Wave Energy Converters (WECs) are arranged in several rows or in a farm '. WECs in a farm are interacting (e.g. The presence of other WECs influence the operational behaviour of a single WEC) and the overall power absorption is affected. In this paper wake effects in the lee of a single WEC and multiple WECs of the overtopping type, where the water volume of overtopped waves is first captured in a basin above mean sea level and then drains back to the sea through hydro turbines, are studied in a time-dependent mild-slope equation model. The wake behind a single WEC is investigated for uni- and multi-directional incident waves. The wake becomes wider for larger wave peak periods. An increasing directional spreading results in a faster wave regeneration and a shorter wake behind the WEC. The wake in the lee of multiple WECs is calculated for two different farm lay-outs, i.e. an aligned grid and a staggered grid, with varying lateral and longitudinal spacing. In general, the staggered grid results in the highest overall wave power absorption. Copyright © 2009 by ASME.
• Broxton, P. D., Troch, P. A., & Lyon, S. W. (2009). On the role of aspect to quantify water transit times in small mountainous catchments. WATER RESOURCES RESEARCH, 45.
• Broxton, P. D., Troch, P. A., & Lyon, S. W. (2009). On the role of aspect to quantify water transit times in small mountainous catchments. Water Resources Research, 45(8).
• Doncker, L. D., Troch, P., Verhoeven, R., Bal, K., Meire, P., & Quintelier, J. (2009). Determination of the Manning roughness coefficient influenced by vegetation in the river Aa and Biebrza river. Environmental Fluid Mechanics, 9(5), 549-567.
  More info

  Abstract: The aim of this study was to investigate the variation of channel bed roughness in two rivers, as important parameter in hydraulic modelling especially with regard to flood control. The universities of Ghent (UG) and Antwerp (UA) are conducting scientific research in the river Aa in Belgium and the Biebrza river in Poland in order to better understand the phenomena involved and to come to a more accurate determination of the different parameters influencing flow. In this paper, the determination of the roughness coefficient 'n' from the Manning equation is used. This coefficient is not easy to determine and is varying constantly. It is influenced by the meandering character of the river, the bed material and the average grain size, the channel bed forms, the channel obstructions, the geometry changes between sections and the vegetation in the channel. Furthermore, due to these parameters, the roughness of the channel is not equally distributed over the channel, the banks and the floodplains. So, using literature data does not always lead to satisfactory results, due to the different situation in the field (Werner et al. J Hydrol 314:139 - 157, 2005). Therefore, measurements are necessary to determine the variation of the Manning coefficient. The Manning coefficient is a function of the discharge, but will also vary over the time due to the mentioned influences. In a multidisciplinary research project on the fundamental exchange processes in river ecosystems, hydraulic measurements were performed on a regular base in the river Aa. During these measurement campaigns, velocity and discharge measurements were carried out in multiple cross-sections. Once a month, the discharge and the water levels were measured at the upstream and the downstream end of the test stretch. On the river Biebrza, similar intensive measurement campaigns took place along a 6 km stretch in the upstream part of the river. An accurate determination of the Manning coefficient according a seasonal variation is an important tool in hydraulic modelling. © Springer Science+Business Media B.V. 2009.
• Doncker, L. d., Troch, P., Verhoeven, R., Bal, K., Desmet, N., & Meire, P. (2009). Relation between resistance characteristics due to aquatic weed growth and the hydraulic capacity of the river AA. River Research and Applications, 25(10), 1287-1303.
  More info

  Abstract: Vegetation growth drastically influences water levels and flow patterns in lowland rivers. As soon as plants start to grow in spring, the flow resistance increases to reach a maximum in early summer. The universities of Ghent and Antwerp are conducting scientific research in the river Aa in Belgium in order to better understand the relation between aquatic weed growth and the hydraulic capacity of the river and to come to a more accurate determination of the different influencing parameters. Velocity measurements are performed in multiple cross-sections on a regular basis and studied. Discharge calculations are based on velocity measurements, which deliver important information about structural characteristics of the river, presence of vegetation, etc. Removing the vegetation allows for determining species and vegetation density as well as for studying the influence of plants on flow distribution and patterns. It is shown that the resistance coefficient, influenced by the amount of biomass, is an important parameter for the hydraulic characteristics of the river. The presence of macrophytes and their blockage characteristics are studied and a relation between discharge, biomass and resistance coefficient is set up. This leads to more reliable results in the application of hydraulic models for river management and river restoration purposes. © 2009 John Wiley & Sons, Ltd.
• Geeraerts, J., Kortenhaus, A., González-Escrivá, J., Rouck, J. D., & Troch, P. (2009). Effects of new variables on the overtopping discharge at steep rubble mound breakwaters - The Zeebrugge case. Coastal Engineering, 56(2), 141-153.
  More info

  Abstract: This paper describes on the one hand parametric tests on wave overtopping for a steep rubble mound breakwater in Zeebrugge, Belgium. On the other hand the comparison between prototype measurements at the breakwater and their scale reproductions in two laboratories is dealt with. The objective is to gain information on possible scale and model effects for wave overtopping from this comparison. The prototype measurements are described together with the resulting dataset of 11 storms where wave overtopping occurred. Scale models and the laboratory measurements are described into detail mentioning similarities and differences to the prototype. Several model effects are identified and special attention is given to wind effects and to the placement pattern of the armour units, respectively. Monte Carlo simulations have been performed to get an idea about the influence of selected model uncertainties. Finally, scale effects are discussed and the influence of model and scale effects for the performed tests is quantified. Recommendations on how to treat these effects are presented. © 2008 Elsevier B.V. All rights reserved.
• Griffiths, P. G., Magirl, C. S., Webb, R. H., Pytlak, E., Troch, P. A., & Lyon, S. W. (2009). Spatial distribution and frequency of precipitation during an extreme event: July 2006 mesoscale convective complexes and floods in southeastern Arizona. WATER RESOURCES RESEARCH, 45.
• Griffiths, P. G., Magirl, C. S., Webb, R. H., Pytlak, E., Troch, P. A., & Lyon, S. W. (2009). Spatial distribution and frequency of precipitation during an extreme event: July 2006 mesoscale convective complexes and floods in southeastern Arizona. Water Resources Research, 45(7).
• Hopp, L., Harman, C., Desilets, S. L., Graham, C. B., McDonnell, J. J., & Troch, P. A. (2009). Hillslope hydrology under glass: Confronting fundamental questions of soil-water-biota co-evolution at Biosphere 2. Hydrology and Earth System Sciences, 13(11), 2105-2118.
  More info

  Abstract: Recent studies have called for a new unifying hydrological theory at the hillslope and watershed scale, emphasizing the importance of coupled process understanding of the interactions between hydrology, ecology, pedology, geochemistry and geomorphology. The Biosphere 2 Hillslope Experiment is aimed at tackling this challenge and exploring how climate, soil and vegetation interact and drive the evolution of the hydrologic hillslope behavior. A set of three large-scale hillslopes (18 m by 33 m each) will be built in the climate-controlled experimental biome of the Biosphere 2 facility near Tucson, Arizona, USA. By minimizing the initial physical complexity of these hillslopes, the spontaneous formation of flow pathways, soil spatial heterogeneity, surface morphology and vegetation patterns can be observed over time. This paper documents the hydrologic design process for the Biosphere 2 Hillslope Experiment, which was based on design principles agreed upon among the Biosphere 2 science community. Main design principles were that the hillslopes should promote spatiotemporal variability of hydrological states and fluxes, facilitate transient lateral subsurface flow without inducing overland flow and be capable of supporting vegetation. Hydrologic modeling was used to identify a hillslope configuration (geometry, soil texture, soil depth) that meets the design objectives. The recommended design for the hillslopes consists of a zero-order basin shape with a 10 degree overall slope, a uniform soil depth of 1 m and a loamy sand soil texture. The sensitivity of the hydrologic response of this design to different semi-arid climate scenarios was subsequently tested. Our modeling showed that the timing of rainfall in relation to the timing of radiation input controls the spatiotemporal variability of moisture within the hillslope and the generation of lateral subsurface flow. The Biosphere 2 Hillslope Experiment will provide an excellent opportunity to test hypotheses, observe emergent patterns and advance the understanding of interactions.
• Hurkmans, R. T., Terink, W., Uijlenhoet, R., Moors, E. J., Troch, P. A., & Verburg, P. H. (2009). Effects of land use changes on streamflow generation in the Rhine basin. Water Resources Research, 45(6).
  More info

  Abstract: The hydrological regime of the Rhine basin is expected to shift from a combined snowmelt-rainfall regime to a more rainfall-dominated regime because of climate change, leading to more extreme flood peaks and low flows. Land use changes may reinforce the effects of this shift through urbanization or may counteract them through, for example, afforestation. In this study, we investigate the effect of projected land use change scenarios on river discharge. Sensitivity of mean and extreme discharge in the Rhine basin to land use changes is investigated at various spatial scales. The variable infiltration capacity (VIC) (version 4.0.5) model is used for hydrological modeling forced by a high-resolution atmospheric data set spanning the period 1993-2003. The model is modified to allow for bare soil evaporation and canopy evapotranspiration simultaneously in sparsely vegetated areas, as this is more appropriate for simulating seasonal effects. All projected land use change scenarios lead to an increase in streamflow. The magnitude of the increase, however, varies among subbasins of different scales from about 2% in the upstream part of the Rhine (about 60,000 km2) to about 30% in the Lahn basin (about 7000 km2). Streamflow at the basin outlet proved rather insensitive to land use changes because over the entire basin affected areas are relatively small. Moreover, projected land use changes (urbanization and conversion of cropland into (semi)natural land or forest) have opposite effects. At smaller scales, however, the effects can be considerable. Copyright 2009 by the American Geophysical Union.
• Hurkmans, R., Terink, W., Uijlenhoet, R., Moors, E. J., Troch, P. A., & Verburg, P. H. (2009). Effects of land use changes on streamflow generation in the Rhine basin. Water Resources Research, 45(6).
• Hurkmans, R., Troch, P. A., Uijlenhoet, R., Torfs, P., & Durcik, M. (2009). Effects of Climate Variability on Water Storage in the Colorado River Basin. JOURNAL OF HYDROMETEOROLOGY, 10(5), 1257-1270.
• Hurkmans, R., Troch, P. A., Uijlenhoet, R., Torfs, P., & Durcik, M. (2009). Effects of climate variability on water storage in the Colorado river basin. Journal of Hydrometeorology, 10(5), 1257-1270.
  More info

  Abstract: Understanding the long-term (interannual-decadal) variability of water availability in river basins is paramount for water resources management. Here, the authors analyze time series of simulated terrestrial water storage components, observed precipitation, and discharge spanning 74 yr in the Colorado River basin and relate them to climate indices that describe variability of sea surface temperature and sea level pressure in the tropical and extratropical Pacific. El Niño-Southern Oscillation (ENSO) indices in winter [January-March (JFM)] are related to winter precipitation as well as to soil moisture and discharge in the lower Colorado River basin. The low-frequency mode of the Pacific decadal oscillation (PDO) appears to be strongly correlated with deep soil moisture. During the negative PDO phase, saturated storage anomalies tend to be negative and the "amplitudes" (mean absolute anomalies) of shallow soil moisture, snow, and discharge are slightly lower compared to periods of positive PDO phases. Predicting interannual variability, therefore, strongly depends on the capability of predicting PDO regime shifts. If indeed a shift to a cool PDO phase occurred in the mid-1990s, as data suggest, the current dry conditions in the Colorado River basin may persist. © 2009 American Meteorological Society.
• Huxman, T., Troch, P., Chorover, J., Breshears, D. D., Saleska, S., Pelletier, J., Zeng, X., & Espeleta, J. (2009). The hills are alive: Earth science in a controlled environment. Eos, 90(14), 120.
• Ingram, D. M., Gao, F., Causon, D. M., Mingham, C. G., & Troch, P. (2009). Numerical investigations of wave overtopping at coastal structures. Coastal Engineering, 56(2), 190-202.
  More info

  Abstract: Under the numerical modelling work package of the EU funded CLASH project, the time accurate, free surface capturing, incompressible Navier-Stokes solver AMAZON-SC has been applied to study impulsive wave overtopping at Samphire Hoe, near Dover in the United Kingdom. The simulations show that the overtopping process on this vertical, sheet pile, seawall is dominated by impulsive, aerated, near vertical overtopping jets. In order to perform the simulations AMAZON-SC has been extended to incorporate an isotropic porosity model and for validation purposes the solver has been applied to study overtopping of a low crested sea dike and a 10:1 battered wall. The results obtained for the battered wall and Samphire Hoe tests are in good agreement both with predicted overtopping discharges calculated using the UK overtopping manual and with available experimental results. © 2008 Elsevier B.V. All rights reserved.
• Li, T. Q., Troch, P., & Rouck, J. D. (2009). Numerical simulation of landslide-induced water wave kinematics by LVOF. Proceedings of the Coastal Engineering Conference, 1249-1261.
  More info

  Abstract: By implementing our design of the mass-force coupling scheme for slamming[6,7], we present some results for case studies related to landslide-induced tsunami modelling in a numerical wave tank, based on our highly efficient Navier-Stokes solver[4,5], named LVOF. LVOF is constructed by a novel VOF finite volume approach that incorporates surface tension, coupled with a dynamic subgrid-scale (SGS) turbulence model. Theoretically, our mass-force coupling model represents the coupling of a moving rigid body on the flow. More importantly, landslides are treated as a fluid, leading to the resulting discrete equations are resolved over the entire domain. Test cases concern aerial and submerged landslides in 2D and 3D, respectively. By comparison, our design of the model is of high efficiency according to the contributions from the mass-force term, raising in the Navier-Stokes equations. On the other hand, our results can also provide valuable base for the analysis of near-field characteristics of landslide generated impulsive waves, by LVOF. © 2009 World Scientific Publishing Co. Pte. Ltd.
• Lyon, S. W., Desilets, S. L., & Troch, P. A. (2009). A tale of two isotopes: Differences in hydrograph separation for a runoff event when using δD versus δ¹⁸O. Hydrological Processes, 23(14), 2095-2101.
  More info

  Abstract: It is often assumed that stable water isotopes (δD and δ 18O) provide redundant information for a given sample of water. In this note we illustrate that the choice of isotope used may influence the resultant hydrograph separation. This is especially true in light of the spatial and temporal variability in the isotopic composition of rainfall water at the catchment scale. We present several possible hydrograph separations based on both δD and δ 18O observed in rainfall for a single runoff event occurring in the southwest USA. This study demonstrates the potential of using both stable water isotopes by showing that δD and δ 18O may provide unique information for catchment hydrologists. We also report on the utility of new technology capable of simultaneous measurements of both δD and δ18O using off-axis integrated cavity output spectroscopy (OA-ICOS) methods. This may be of interest to catchment hydrologists seeking to incorporate this type of equipment into their laboratory. Copyright © 2009 John Wiley & Sons, Ltd.
• Lyon, S. W., Desilets, S., & Troch, P. A. (2009). A tale of two isotopes: Differences in hydrograph separation for a runoff event when using ??D versus ??18O. Hydrological Processes, 23(14), 2095-2101.
• Lyon, S. W., Desilets, S., & Troch, P. A. (2009). A tale of two isotopes: differences in hydrograph separation for a runoff event when using delta D versus delta O-18. HYDROLOGICAL PROCESSES, 23(14), 2095-2101.
• Lyon, S. W., Destouni, G., Giesler, R., Humborg, C., Mörth, M., Seibert, J., Karlsson, J., & Troch, P. A. (2009). Estimation of permafrost thawing rates in a sub-arctic catchment using recession flow analysis. Hydrology and Earth System Sciences, 13(5), 595-604.
  More info

  Abstract: Permafrost thawing is likely to change the flow pathways taken by water as it moves through arctic and sub-arctic landscapes. The location and distribution of these pathways directly influence the carbon and other biogeochemical cycling in northern latitude catchments. While permafrost thawing due to climate change has been observed in the arctic and sub-arctic, direct observations of permafrost depth are difficult to perform at scales larger than a local scale. Using recession flow analysis, it may be possible to detect and estimate the rate of permafrost thawing based on a long-term streamflow record. We demonstrate the application of this approach to the sub-arctic Abiskojokken catchment in northern Sweden. Based on recession flow analysis, we estimate that permafrost in this catchment may be thawing at an average rate of about 0.9 cm/yr during the past 90 years. This estimated thawing rate is consistent with direct observations of permafrost thawing rates, ranging from 0.7 to 1.3 cm/yr over the past 30 years in the region. © 2009 Author(s).
• Margheritini, L., Victor, L., Kofoed, J. P., & Troch, P. (2009). Geometrical optimization for improved power capture of multi-level overtopping based wave energy converters. Proceedings of the International Offshore and Polar Engineering Conference, 339-344.
  More info

  Abstract: In multi-level wave energy converters the water from incoming waves is stored in reservoirs one on top of the other. Prevision formula for the overtopping flow rates in the individual reservoirs is fundamental for dimensioning correctly the turbines and optimizing the device. Having a number of reservoirs one on top of each other means that the representative overtopping formulae for coastal structures are not sufficient to describe the phenomena. This paper proposes to describe the dependence of the overtopping on a new parameter which is the horizontal distance between the reservoirs or, in other words, the opening between two consecutive reservoirs. 13 different geometries have been tested in 2D irregular waves and a new formulation for prediction of overtopping in multilevel structures is presented. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).
• Margheritini, L., Victor, L., Kofoed, J. P., & Troch, P. (2009). Geometrical optimization for improved power capture of multi-level overtopping based wave energy converters. Proceedings of the International Offshore and Polar Engineering Conference.
  More info

  Abstract: In multi-level wave energy converters, water from incoming waves is stored in reservoirs one on top of the other. Prevision formula for the overtopping flow rates in the individual reservoirs is fundamental for dimensioning correctly the turbines and optimizing the device. A study was carried out to describe the dependence of the overtopping on a new parameter, i.e., the horizontal distance (HD) between the reservoirs. The overtopping in the lower reservoir increased with increasing HD. Overtopping in the upper reservoir decreased with increasing HD. A threshold after which the parameter HD may increase or decrease the overall efficiency of the device exists. Two different formulations of the overtopping prediction formula by Kofoed 2002 were derived, which can account for the HD parameter. This is an abstract of a paper presented at the 2009 International Offshore and Polar Engineering Conference (Osaka, Japan 6/21-26/2009).
• Switanek, M. B., Troch, P. A., & Castro, C. L. (2009). Improving Seasonal Predictions of Climate Variability and Water Availability at the Catchment Scale. JOURNAL OF HYDROMETEOROLOGY, 10(6), 1521-1533.
• Switanek, M. B., Troch, P. A., & Castro, C. L. (2009). Improving seasonal predictions of climate variability and water availability at the catchment scale. Journal of Hydrometeorology, 10(6), 1521-1533.
  More info

  Abstract: In a water-stressed region, such as the southwestern United States, it is essential to improve current seasonal hydroclimatic predictions. Typically, seasonal hydroclimatic predictions have been conditioned by standard climate indices, for example, Niño-3 and Pacific decadal oscillation (PDO). In this work, the statistically unique relationships between sea surface temperatures (SSTs) and particular basins' hydroclimates are explored. The regions where global SSTs are most correlated with the Little Colorado River and Gunnison River basins' hydroclimates are located throughout the year and at varying time lags. The SSTs, from these regions of highest correlation, are subsequently used as hydroclimatic predictors for the two basins. This methodology, named basin-specific climate prediction (BSCP), is further used to perform hindcasts. The hydroclimatic hindcasts obtained using BSCP are shown to be closer to the historical record, for both basins, than using the standard climate indices as predictors. © 2009 American Meteorological Society.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2009). On the study of impulsive waves caused by landslides. Proceedings of the International Offshore and Polar Engineering Conference, 1264-1273.
  More info

  Abstract: By extending LVOF to a two-phase model, we study impulsive waves created by landslides, based on our design of the mass-force coupling model (Li et al., 2007a; 2008). LVOF is a highly efficient Navier-Stokes solver, constructed by a novel VOF finite volume cut-cell approach that incorporates surface tension plus a dynamic subgrid-scale model (Li et al., 2004; 2007). According to the fictitious domain method, the mass-force model represents the coupling of a moving body on the flow, by handling the rigid body distributed over the particle domain as a fluid. Additionally, a ghost cell method (GFM) is used to treat the boundary conditions near the particle-fluid interface. Grid refinement studies are performed for test problems involving aerial landslides. Very encouragingly, the results agree well with measurements available. It is demonstrated that our results can provide valuable base for the analysis of near-field characteristics of landslide generated impulsive waves, by LVOF. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).
• Troch, P. A., Carrillo, G. A., Heidbüchel, I., Rajagopal, S., Switanek, M., Volkmann, T. H., & Yaeger, M. (2009). Dealing with landscape heterogeneity in watershed hydrology: A review of recent progress toward new hydrological theory. Geography Compass, 3(1), 375-392.
  More info

  Abstract: Predictions of hydrologic system response to natural and anthropogenic forcing are highly uncertain due to the heterogeneity of the land surface and subsurface. Landscape heterogeneity results in spatiotemporal variability of hydrological states and fluxes, scale-dependent flow and transport properties, and incomplete process understanding. Recent community activities, such as Prediction in Ungauged Basins of International Association of Hydrological Sciences, have recognized the impasse current catchment hydrology is facing and have called for a focused research agenda toward new hydrological theory at the watershed scale. This new hydrological theory should recognize the dominant control of landscape heterogeneity on hydrological processes, should explore novel ways to account for its effect at the watershed scale, and should build on an interdisciplinary understanding of how feedback mechanisms between hydrology, biogeochemistry, pedology, geomorphology, and ecology affect catchment evolution and functioning. © 2009 Blackwell Publishing Ltd.
• Troch, P. A., Martinez, G. F., Pauwels, V., Durcik, M., Sivapalan, M., Harman, C., Brooks, P. D., Gupta, H., & Huxman, T. (2009). Climate and vegetation water use efficiency at catchment scales. HYDROLOGICAL PROCESSES, 23(16), 2409-2414.
• Troch, P. A., Martinez, G. F., Pauwels, V., Durcik, M., Sivapalan, M., Harman, C., Brooks, P. D., Gupta, H., & Huxman, T. (2009). Climate and vegetation water use efficiency at catchment scales. Hydrological Processes, 23(16), 2409-2414.
• Vos, L. D., Troch, P., & Rouck, J. D. (2009). Experimental analysis of scale effects of the wave induced flow field around a monopile using particle image velocimetry. Proceedings of the Coastal Engineering Conference, 3757-3769.
  More info

  Abstract: An offshore monopile has an influence on the local flow field. When no countermeasures are taken, the disturbed flow field generally leads to local scouring of the sea bed. Often, the expected scour depth is not acceptable for the stability of the structure and the application of a scour bottom protection is required. For the design of the extent of the scour protection, it is valuable to investigate the area in which the flow field is disturbed by the presence of the structure. The disturbed velocity profile around the base of a monopile structure is investigated using Particle Image Velocimetry (PIV) measurements in a scale model of the monopile in two physical wave flumes. PIV is a powerful measuring technique to obtain instantaneous whole flow field measurements. To assess possible scale effects, the PIV measurements are carried out at two different scales. The velocity fields in non-breaking and breaking regular wave conditions are measured on both scales. The results show only a limited influence of the breaking process on the flow velocities near the bottom. However, a significant influence of the scale on the behaviour of the flow separation is noticed. © 2009 World Scientific Publishing Co. Pte. Ltd.
• Bogaart, P. W., Teuling, A. J., & Troch, P. A. (2008). A state-dependent parameterization of saturated-unsaturated zone interaction. Water Resources Research, 44(11).
• Delecluyse, K., Brantegem, W., Troch, P., Verhoeven, R., & Vierendeels, J. (2008). Validation of a CFD model for flow in meandering rivers using an experimental test-setup: First results. WIT Transactions on Engineering Sciences, 59, 55-64.
  More info

  Abstract: A 3D Reynolds Averaged Navier Stokes (RANS) model of a meandering channel with rectangular cross-section has been developed using the commercial software package FLUENT 6.2. This model solves the 3D Navier-Stokes equations using the PISO scheme for the pressure-velocity coupling and the realizable k-?̊ model for turbulence closure. Output of the numerical model is compared to validation experiments conducted in a physical model, which represents two wavelengths of a regime channel and allows for the measurement of flow patterns at several discharges and variable bed forms. The computed water depths and velocity profiles of the CFD model output are in good agreement with the physical model results. The simulations slightly underpredict the streamwise velocities, which reach a maximum just before the apex of the meander bend, at the inner bank in the lower part of the flow depth. The CFD model also captures the motion of the secondary current or transverse flow well, showing the same direction of current along the entire second wavelength. © 2008 WIT Press.
• Desilets, S., Ferr??, T., & Troch, P. A. (2008). Effects of stream-aquifer disconnection on local flow patterns. Water Resources Research, 44(9).
• Desilets, S., Ferre, T., & Troch, P. A. (2008). Effects of stream-aquifer disconnection on local flow patterns. WATER RESOURCES RESEARCH, 44(9).
• Doncker, L. D., Troch, P., & Verhoeven, R. (2008). Accuracy of discharge measurements in a vegetated river. Flow Measurement and Instrumentation, 19(1), 29-40.
  More info

  Abstract: Hydraulic measurements are necessary to calibrate numerical models and to collect information about the situation under field and laboratory conditions. The accuracy of the measurements depends on several factors. Laboratory research is carried out to evaluate the accuracy of different techniques and methods under well-controlled conditions. Field measurements are performed to evaluate the impact of natural conditions on the accuracy of the measurements. The better the quality of the discharge measurements, the more possible is the reliable determination of the roughness coefficient, leading to an improved accuracy of hydraulic modelling. Several measurement techniques and instruments (as hydrometric propellers and electromagnetic devices) are discussed in this paper. Furthermore, the possibility of continuous measurements is researched, next to the influence of the macrophytes on discharge measurement in vegetated rivers. © 2007 Elsevier Ltd. All rights reserved.
• Doncker, L. D., Verhoeven, R., Troch, P., Desmet, N., Meire, P., & Seuntjes, P. (2008). Influence of vegetation on the propagation of flood waves. WIT Transactions on Engineering Sciences, 59, 331-339.
  More info

  Abstract: Research on river ecosystems asks for a multidisciplinary approach. All components such as water, macrophytes, sediment, suspended solids, etc. play an important role. The presence of macrophytes in rivers has an influence on water levels and flow patterns since a wealthy vegetation growth causes back water effects and consequently higher upstream water levels. In view of this, flood risk increases in periods of higher flows and greater vegetation growth. So, river management also deals with the control of vegetation. Good management contributes not only to the quality of the water and the ecosystem, but also to flood protection. © 2008 WIT Press.
• Guardiola-Claramonte, M., Troch, P. A., Ziegler, A. D., Giambelluca, T. W., Vogler, J. B., & Nullet, M. A. (2008). Local hydrologic effects of introducing non-native vegetation in a tropical catchment. ECOHYDROLOGY, 1(1), 13-22.
• Hasan, S., Troch, P. A., Bogaart, P. W., & Kroner, C. (2008). Evaluating catchment-scale hydrological modeling by means of terrestrial gravity observations. WATER RESOURCES RESEARCH, 44(8).
• Hasan, S., Troch, P. A., Bogaart, P. W., & Kroner, C. (2008). Evaluating catchment-scale hydrological modeling by means of terrestrial gravity observations. Water Resources Research, 44(8).
• Hurkmans, R. T., Moel, H. D., Aerts, J. C., & Troch, P. A. (2008). Water balance versus land surface model in the simulation of Rhine river discharges. Water Resources Research, 44(1).
  More info

  Abstract: Accurate streamflow simulations in large river basins are crucial to predict timing and magnitude of floods and droughts and to assess the hydrological impacts of climate change. Water balance models have been used frequently for these purposes. Compared to water balance models, however, land surface models carry the potential to more accurately estimate hydrological partitioning and thus streamflow, because they solve the coupled water and energy balance and are able to exploit a larger part of the information provided by regional climate model output than water balance models. Owing to increased model complexity, however, they are also more difficult to parameterize. The purpose of this study is to investigate and compare the accuracy of streamflow simulations of a water balance approach (Spatial Tools for River basins and Environment and Analysis of Management (STREAM)) and a land surface model (Variable Infiltration Capacity (VIC)) approach. Both models are applied to the Rhine river basin using regional climate model output as atmospheric forcing, and are evaluated using observed streamflow and lysimeter data. We find that VIC is more robust and less dependent on model calibration. Although STREAM performs better during the calibration period (Nash-Sutcliffe efficiency (E) of 0.47 versus E = 0.29 for VIC), VIC more accurately simulates discharge during the validation period, including peak flows (E = 0.31 versus E = 0.21 for STREAM). This is the case for most locations throughout the basin, except for the Alpine part where both models have difficulties due to the complex terrain and surface reservoirs. In addition, the annual evaporation cycle at the lysimeters is more realistically simulated by VIC. Copyright 2008 by the American Geophysical Union.
• Hurkmans, R., De Moel, H., Aerts, J., & Troch, P. A. (2008). Water balance versus land surface model in the simulation of Rhine river discharges. Water Resources Research, 44(1).
• Lyon, S. W., Desilets, S., & Troch, P. A. (2008). Characterizing the response of a catchment to an extreme rainfall event using hydrometric and isotopic data. WATER RESOURCES RESEARCH, 44(6).
• Lyon, S. W., Desilets, S., & Troch, P. A. (2008). Characterizing the response of a catchment to an extreme rainfall event using hydrometric and isotopic data. Water Resources Research, 44(6).
• Lyon, S. W., L., S., & Troch, P. A. (2008). Characterizing the response of a catchment to an extreme rainfall event using hydrometric and isotopic data. Water Resources Research, 44(6).
  More info

  Abstract: [1] In this study we investigate an event-scale transit time distribution (TTD) for a catchment located in the Santa Catalina Mountains northeast of downtown Tucson, Arizona, USA, during a series of extreme rainfall events. Traditionally, TTD studies look at the long time response of a catchment to an input variation in tracer concentration. Few studies have determined the TTD at the scale of an event. Isotopic and hydrometric data collected during the event considered in this study provide the unique opportunity to characterize the response of the catchment under extreme conditions using both TTD modeling and hydrograph separation. This revealed similarity in the shapes of the event TTD and event water recession hydrograph. Also, the first moment of the event water recession hydrograph and the mean transit time of the TTD were similar. Because of the extreme nature of this event, it is likely that the catchment reaches and relaxes from the maximum possible storage, making its response a time-invariant characteristic of the catchment on the basis of hydraulic theory. The similarity between the event water recession and event TTD during this characteristic response of the catchment may, thus, allow for the derivation of a time-invariant event TTD. This result is especially valuable as it lays a basis for catchment similarity analysis linking a catchment's hydrological response and geomorphic properties. Copyright 2008 by the American Geophysical Union.
• Lyon, S. W., Troch, P. A., Broxton, P. D., Molotch, N. P., & Brooks, P. D. (2008). Monitoring the timing of snowmelt and the initiation of streamflow using a distributed network of temperature/light sensors. ECOHYDROLOGY, 1(3), 215-224.
• Talebi, A., Troch, P. A., & Uijlenhoet, R. (2008). A steady-state analytical slope stability model for complex hillslopes. HYDROLOGICAL PROCESSES, 22(4), 546-553.
• Talebi, A., Troch, P. A., & Uijlenhoet, R. (2008). A steady-state analytical slope stability model for complex hillslopes. Hydrological Processes, 22(4), 546-553.
  More info

  Abstract: This paper presents a steady-state analytical hillslope stability model to study the role of topography on rain-induced shallow landslides. We combine a bivariate continuous function of the topographic surface, a steady-state hydrological model of hillslope saturated storage, and the infinite slope stability assumption to investigate the interplay between terrain characteristics, saturated storage within hillslopes and soil mechanics. We demonstrate the model by examining the stability of nine characteristic hillslope types (landform elements) with three different profile curvatures (concave, straight and convex) and three different plan shapes (convergent, parallel and divergent). For each hillslope type, the steady-state saturated storage corresponding to given recharge rates is computed for three different average bedrock slope angles. On the basis of the infinite slope stability method, the factor of safety (FS) along the hillslopes is determined. Our results demonstrate that in the steep slopes, the least stable situation occurs in hillslopes with convergent plan shapes and concave length profiles, while the convex ones are more stable. In addition to testing our method for nine characteristic hillslope types, a general relationship between plan shape and profile curvature of landform elements and the factor of safety is derived for a pre-defined hillslope length scale. Our results show that slope stability increases when profile curvature changes from concave to convex. In terms of plan shapes, changing from convergent to divergent, slope stability increases for all length profiles. However, we find that the effect of plan shape is more pronounced for convex length profiles. Overall, we demonstrate that, in addition to bedrock slope, hillslope shape as represented by plan shape and profile curvature is an important control on hillslope stability. Copyright © 2007 John Wiley & Sons, Ltd.
• Talebi, A., Uijlenhoet, R., & Troch, P. A. (2008). A low-dimensional physically based model of hydrologic control of shallow landsliding on complex hillslopes. EARTH SURFACE PROCESSES AND LANDFORMS, 33(13), 1964-1976.
• Talebi, A., Uijlenhoet, R., & Troch, P. A. (2008). A low-dimensional physically based model of hydrologic control of shallow landsliding on complex hillslopes. Earth Surface Processes and Landforms, 33(13), 1964-1976.
  More info

  Abstract: Hillslopes have complex three-dimensional shapes that are characterized by their plan shape, profile curvature of surface and bedrock, and soil depth. To investigate the stability of complex hillslopes (with different slope curvatures and plan shapes), we combine the hillslopestorage Boussinesq (HSB) model with the infinite slope stability method. The HSB model is based on the continuity and Darcy equations expressed in terms of storage along the hillslope. Solutions of the HSB equation account explicitly for plan shape by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function. The presented model is composed of three parts: a topography model conceptualizing three-dimensional soil mantled landscapes, a dynamic hydrology model for shallow subsurface flow and water table depth (HSB model) and an infinite slope stability method based on the Mohr-Coulomb failure law. The resulting hillslope-storage Boussinesq stability model (HSB-SM) is able to simulate rain-induced shallow landsliding on hillslopes with non-constant bedrock slope and non-parallel plan shape. We apply the model to nine characteristic hillslope types with three different profile curvatures (concave, straight, convex) and three different plan shapes (convergent, parallel, divergent). In the presented model, the unsaturated storage has been calculated based on the unit head gradient assumption. To relax this assumption and to investigate the effect of neglecting the variations of unsaturated storage on the assessment of slope stability in the transient case, we also combine a coupled model of saturated and unsaturated storage and the infinite slope stability method. The results show that the variations of the unsaturated zone storage do not play a critical role in hillslope stability. Therefore, it can be concluded that the presented dynamic slope stability model (HSB-SM) can be used safely for slope stability analysis on complex hillslopes. Our results show that after a certain period of rainfall the convergent hillslopes with concave and straight profiles become unstable more quickly than others, whilst divergent convex hillslopes remain stable (even after intense rainfall). In addition, the relation between subsurface flow and hillslope stability has been investigated. Our analyses show that the minimum safety factor (FS) occurs when the rate of subsurface flow is a maximum. In fact, by increasing the subsurface flow, stability decreases for all hillslope shapes. Copyright © 2008 John Wiley & Sons, Ltd.
• Talebi, A., Uijlenhoet, R., & Troch, P. A. (2008). Application of a probabilistic model of rainfall-induced shallow landslides to complex hollows. Natural Hazards and Earth System Science, 8(4), 733-744.
  More info

  Abstract: Recently, D'Odorico and Fagherazzi (2003) proposed "A probabilistic model of rainfall-triggered shallow landslides in hollows" (Water Resour. Res., 39, 2003). Their model describes the long-term evolution of colluvial deposits through a probabilistic soil mass balance at a point. Further building blocks of the model are: an infinite-slope stability analysis; a steady-state kinematic wave model (KW) of hollow groundwater hydrology; and a statistical model relating intensity, duration, and frequency of extreme precipitation. Here we extend the work of D'Odorico and Fagherazzi (2003) by incorporating a more realistic description of hollow hydrology (hillslope storage Boussinesq model, HSB) such that this model can also be applied to more gentle slopes and hollows with different plan shapes. We show that results obtained using the KW and HSB models are significantly different as in the KW model the diffusion term is ignored. We generalize our results by examining the stability of several hollow types with different plan shapes (different convergence degree). For each hollow type, the minimum value of the landslide-triggering saturated depth corresponding to the triggering precipitation (critical recharge rate) is computed for steep and gentle hollows. Long term analysis of shallow landslides by the presented model illustrates that all hollows show a quite different behavior from the stability view point. In hollows with more convergence, landslide occurrence is limited by the supply of deposits (supply limited regime) or rainfall events (event limited regime) while hollows with low convergence degree are unconditionally stable regardless of the soil thickness or rainfall intensity. Overall, our results show that in addition to the effect of slope angle, plan shape (convergence degree) also controls the subsurface flow and this process affects the probability distribution of landslide occurrence in different hollows. Finally, we conclude that incorporating a more realistic description of hollow hydrology (instead of the KW model) in landslide probability models is necessary, especially for hollows with high convergence degree which are more susceptible to landsliding.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2008). Numerical simulation of water impact in 3D by LVOF. Proceedings of the International Offshore and Polar Engineering Conference, 1-7.
  More info

  Abstract: Based on our highly efficient Navier-Stokes solver, LVOF (Li, et al., 2004, 2007), we present some results for water entry and exit in a 3D numerical wave tank, by implementing our design of a mass-force coupling scheme for water impact (Li, et al., 2007a). LVOF is constructed by a novel VOF finite volume cut-cells approach that incorporates surface tension, coupled with a dynamic subgrid-scale model. Our mass-force coupling model in theory represents the coupling of a moving body on the flow, which is realized through introducing the internal source function. Importantly, a solid body is treated as a fluid, especially the solid-liquid phase front is captured over a fixed Cartesian grid without smearing the information at the particle-fluid interface. Grid refinement studies are performed for test problems involving the wedge entry and exit. In addition, issue about the convergence performance is addressed under the prescribed entry velocity. Very encouragingly, the results agree with measurements available. It is demonstrated that most of typical features in complex flow patterns can be captured in waves caused by impact, by using LVOF. Copyright © 2008 by The International Society of Offshore and Polar Engineers (ISOPE).
• Doncker, L. D., Troch, P., Verhoeven, R., Bal, K., Meire, P., Chormański, J., Okruszko, T., & Świa̧tek, D. (2007). Impact of vegetation development on the hydraulic characteristics and flow patterns in lowland rivers. Proceedings of the International Conference W3M "Wetlands: Modelling, Monitoring, Management", 165-172.
  More info

  Abstract: Vegetation growth drastically influences water levels and flow patterns in lowland rivers. As soon as plants start to grow in spring, the flow resistance and by this the upstream water levels increase to reach a maximum in early summer. The universities of Ghent and Antwerp are carrying out research in the river Aa (Belgium) and the Biebrza river (Poland) in order to better understand the natural phenomena involved and to come to a more accurate determination of the different parameters involved. Regular field measurement campaigns allow to determine the variation of the roughness coefficient (Manningcoefficient n) as a function of time, type and density of vegetation, hydraulic parameters etc. and to evaluate flow and geomorphology patterns in the vicinity of vegetation patches. During these measurement campaigns, velocity and discharge measurements are carried out in multiple cross-sections in presence of vegetation using both an electromagnetic device and a hydrometric propeller.© 2007 Taylor & Francis Group.
• Geeraerts, J., Troch, P., Rouck, J. D., Verhaeghe, H., & Bouma, J. J. (2007). Wave overtopping at coastal structures: prediction tools and related hazard analysis. Journal of Cleaner Production, 15(16), 1514-1521.
  More info

  Abstract: Safe use of low lying and densely populated coastal regions depends critically on the performance of coastal structures in defending these areas against storm surges, wave attack, flooding and erosion. Continuing sea level rise and climate change (storms are becoming rougher) emphasise the need for reliable and robust predictions as higher storm surges and bigger storms may lead to flooding. Population pressures on land use in coastal regions have sometimes ignored age-old appreciation of coastal hazards. The CLASH research project EVK3-CT-2001-00058 was funded by the EU to provide "Crest Level Assessment of coastal Structures by full scale monitoring, neural network prediction and Hazard analysis on permissible wave overtopping". One of its main objectives was to produce a generally applicable prediction method based on permissible wave overtopping and hazard analysis. This paper describes the problems related to wave overtopping and crest level design of coastal structures. Within the CLASH background, the development of a generic prediction method and its use taking into account hazards is presented. © 2006 Elsevier Ltd. All rights reserved.
• Hilberts, A. G., Troch, P. A., Paniconi, C., & Boll, J. (2007). Low-dimensional modeling of hillslope subsurface flow: Relationship between rainfall, recharge, and unsaturated storage dynamics. Water Resources Research, 43(3).
  More info

  Abstract: [1] We present a coupling between the one-dimensional Richards equation for vertical unsaturated flow and the one-dimensional hillslope-storage Boussinesq equation (HSB) for lateral saturated flow along complex hillslopes. Here the capillary fringe is included in the flow domain as an integral part of the Boussinesq aquifer. The coupling allows quantitative investigation of the role of unsaturated storage in the relationship between rainfall and recharge. The coupled model (HSB coupled) is compared to the original HSB model (HSB original) and a three-dimensional Richards equation (RE) based model (taken to be the benchmark) on a set of seven synthetic hillslopes, ranging from convergent to divergent. Using HSB original, the water tables are overestimated and the outflow rates are generally underestimated, and there is no delay between rainfall and recharge. The coupled model, however, shows a remarkably good match with the RE model in terms of outflow rates, and the delay between rainfall and recharge is captured well. We also see a clear improvement in the match to the water tables, even though the values are still overestimated for some hillslope shapes, in particular the convergent slopes. We show that for the hillslope configurations and scenarios examined in this paper it is possible to reproduce hydrographs and water table dynamics with a good degree of accuracy using a low-dimensional hydrological model. Copyright 2007 by the American Geophysical Union.
• Hilberts, A., Troch, P. A., Paniconi, C., & Boll, J. (2007). Low-dimensional modeling of hillslope subsurface flow: Relationship between rainfall, recharge, and unsaturated storage dynamics. Water Resources Research, 43(3).
• Leen, D. V., Julien, D. R., & Peter, T. (2007). Damage development in scour protections around offshore monopiles. Proceedings of the Coastal Engineering Conference, 2391-2403.
  More info

  Abstract: Some of the best locations for wind-farms are in more or less shallow coastal waters where wind is unobstructed by land. However, when a monopile is placed offshore and no countermeasures are taken, the sea bottom is subject to local scour due to waves and/or currents. Often, the expected scour depth is not acceptable for the structure and scour protection is necessary. A conservative way to design a scour protection (e.g. rip rap) is to allow no or only little displacement of individual rock stones. When the design criterion is no movement and the amplification factor due to the presence of the pile is known, the Shields criterion can be used to calculate the necessary individual stone size. A more economical solution may be building a protection with smaller elements, allowing movement of individual stones without failure of the protection. Under these latter conditions it is important to formulate a clear damage definition, to define an acceptable damage criterion and to account for damage development over time as important elements in the design of scour protections. This paper describes an experimental study on a scour protection of loose rocks around a monopile foundation. For different stone sizes, damage initiation and damage development during a storm is investigated, taking into account the influence of a combined wave and current action. A suggestion for a damage definition for a scour protection around a monopile foundation is made. The test results show that on average, movement of the stones is initiated for a bed shear stress equal to approximately half of the critical bed shear stress (Shields). Damage development over time exhibits an exponential trend. The results further show the importance of investigating the combined action of waves and currents, as damage is highly increased when wave action is superimposed on a steady current (e.g. tidal current). © 2007 World Scientific Publishing Co. Pte. Ltd.
• Li, T. Q., Troch, P., & Rouck, J. D. (2007). A numerical study of coupling of waves with a current over cut-cell mesh. Proceedings of the Coastal Engineering Conference, 666-676.
  More info

  Abstract: In this paper, we further study coupling of surface waves with a current over a cut cell, based on our highly efficient Navier-Stokes solver [3,4], named LVOF. This solver is constructed by a novel VOF finite volume approach that incorporates surface tension, coupled with a dynamic subgrid-scale (SGS) turbulence model. Additionally, we design two types of numerical wave-current generators: an external and internal generators, while the outgoing waves are dissipated by a breaking-type wave absorber placed at the opposite end. Based on LVOF, we wish that our results can provide valuable base for the analysis of wave-current-body interaction, according to the well-designed wave-current generator. © 2007 World Scientific Publishing Co. Pte. Ltd.
• Lyon, S. W., & Troch, P. A. (2007). Hillslope subsurface flow similarity: Real-world tests of the hillslope P??clet number. Water Resources Research, 43(7).
• Lyon, S. W., & Troch, P. A. (2007). Hillslope subsurface flow similarity: Real-world tests of the hillslope Péclet number. Water Resources Research, 43(7).
  More info

  Abstract: Similarity analysis offers the ability to model hydrological response using quantifiable landscape descriptors. It is possible to develop similarity indices based on analytical solutions to the governing dynamic equations (Brutsaert, 2005). Berne et al. (2005) provide derivation of such a similarity index (the hillslope Péclet number) of subsurface flow and saturation for hillslopes with exponential width functions. They showed that the hillslope Péclet number depends only on geometric properties of the hillslope. Their work was validated using laboratory experiments conducted on constructed hillslopes with homogeneous soil structure and varying bedrock slope angle. This study applies the similarity analysis of Berne et al. (2005) to two data sets: (1) the trench hillslope study at the Maimai research catchment conducted by Woods and Rowe (1996) and (2) the isolated hillslope study near Troy, Idaho, United States, conducted by Brooks et al. (2004). The Maimai trench study was selected because it provides subsurface flow data from hillslopes with different planform geometries. The Troy hillslope study was selected because the experimental results of Brooks et al. (2004) provide an estimate of hydraulic conductivity consistent with the support scale of the hillslope. We estimated the hillslope Péclet number of the hillslopes on the basis of elevation data and reported values of average soil depth. This hillslope Péclet number quantifies the geomorphological control on how water moves through these hillslopes and creates a basis for comparison independent of hydraulic properties. We then estimated the first and second moments of the characteristic subsurface response function of each hillslope on the basis of subsurface flow data. To compare the empirical and theoretical moments, the hydraulic properties (saturated hydraulic conductivity and drainable porosity) of the hillslopes were related using a base flow recession analysis. Then we were able to derive the dimensionless moments of the hillslopes' observed characteristic response function using hydraulic conductivities reported in the literature. The agreement between the observed and theoretical moments shows the promise of implementing the hillslope Péclet number as a similarity parameter to describe first-order hydrological response in humid environments. Copyright 2007 by the American Geophysical Union.
• Magirl, C. S., Webb, R. H., Schaffner, M., Lyon, S. W., Griffiths, P. G., Shoemaker, C., Unkrich, C. L., Yatheendradas, S., Troch, P. A., Pytlak, E., Goodrich, D. C., Desilets, S. L., Youberg, A., & Pearthree, P. A. (2007). Impact of recent extreme Arizona storms. Eos, 88(17), 191+193.
• Magirl, C. S., Webb, R. H., Schaffner, M., Lyon, S. W., Griffiths, P. G., Shoemaker, C., Unkrich, C. L., Yatheendradas, S., Troch, P. A., Pytlak, E., Goodrich, D. C., Desilets, S., Youberg, A., & Pearthree, P. A. (2007). Impact of recent extreme Arizona storms. Eos, 88(17).
• Rouck, J. D., Van, B., Troch, P., Van, J., Damme, L. V., Medina, J. R., Willems, M., & Frigaard, P. (2007). Wave run-up on the Zeebrugge rubble mound breakwater: Full-scale measurement results versus laboratory results. Journal of Coastal Research, 23(3), 584-591.
  More info

  Abstract: A clear difference between full-scale wave run-up measurements and small-scale model test results had been noticed during a MAST II project. This finding initiated a thorough study of wave run-up through the European MAST III OPTICREST project. Full-scale measurements have been carried out on the Zeebrugge rubble mound breakwater. This breakwater has been modeled in three laboratories: two 2D models at a scale of 1:30 and one 3D model at a scale of 1:40 have been built at Flanders Hydraulics (Belgium), at Universidad Politécnica de Valencia (Spain), and at Aalborg University (Denmark). Wave run-up has been measured by a digital run-up gauge. This gauge has proven to measure wave run-up more accurately than the traditional wire gauge. Wave spectra measured in Zeebrugge have been reproduced in the laboratories. Results of small-scale model tests and full-scale measurement results have been compared. This comparison confirmed the MAST II outcome: wave run-up is underestimated by small-scale model tests. The difference between full-scale measurement results and small-scale model test results is the result of model effects. The porosity of the armor layer has a significant influence on wave run-up and may explain the dependency of wave run-up on the water level observed in Zeebrugge. An influence of the spectral shape has also been noticed.
• Rouck, J. D., Van, B., Troch, P., Van, J., Damme, L. V., Medina, J. R., Willems, M., & Frigaard, P. (2007). Wave run-up on the Zeebrugge rubble mound breakwater: Full-scale measurement results. Journal of Coastal Research, 23(3), 577-583.
  More info

  Abstract: Full-scale wave run-up measurements have been carried out on the Zeebrugge rubble mound breakwater in the frame of the EU-funded OPTICREST project. Wave run-up has been measured by a run-up gauge and by a so-called spiderweb system. The dimensionless wave run-up value Ru2%/Hm0 measured in Zeebrugge equals 1.77 for Iribarren number ξom = 3.63. An (apparent) influence of the water level on wave run-up has been observed. The porosity of the armor layer has a significant influence on wave run-up and may explain the dependency of wave run-up on the water level observed in Zeebrugge. Full-scale measurement results have been compared to literature data. The full-scale wave run-up data are in good agreement with the existing results of wave run-up tests with rip-rap slopes but are clearly higher than other wave run-up data resulting from tests with rubble mound breakwaters.
• Talebi, A., Uijlenhoet, R., & Troch, P. A. (2007). Soil moisture storage and hillslope stability. Natural Hazards and Earth System Science, 7(5), 523-534.
  More info

  Abstract: Recently, we presented a steady-state analytical hillslope stability model to study rain-induced shallow land-slides. This model is based on kinematic wave dynamics of saturated subsurface storage and the infinite slope stability assumption. Here we apply the model to investigate the effect of neglecting the unsaturated storage on the assessment of slope stability in the steady-state hydrology. For that purpose we extend the hydrological model to compute the soil pore pressure distribution over the entire flow domain. We also apply this model for hillslopes with non-constant soil depth to compare the stability of different hillslopes and to find the critical slip surface in hillslopes with different geometric characteristics. In order to do this, we incorporate more complex approaches to compute slope stability (Janbu's non-circular method and Bishop's simplified method) in the steady-state analytical hillslope stability model. We compare the safety factor (FS) derived from the infinite slope stability method and the more complex approach for two cases: with and without the soil moisture profile in the unsaturated zone. We apply this extended hillslope stability model to nine characteristic hillslope types with three different profile curvatures (concave, straight, convex) and three different plan shapes (convergent, parallel, divergent). Overall, we find that unsaturated zone storage does not play a critical role in determining the factor of safety for shallow and deep land-slides. As a result, the effect of the unsaturated zone storage on slope stability can be neglected in the steady-state hydrology and one can assume the same bulk specific weight below and above the water table. We find that steep slopes with concave profile and convergent plan shape have the least stability. We also demonstrate that in hillslopes with non-constant soil depth (possible deep landslides), the ones with convex profiles and convergent plan shapes have slip surfaces with the minimum safety factor near the outlet region. In general, when plan shape changes from divergent to convergent, stability decreases for all length profiles. Finally, we show that the applied slope stability methods and steady-state hydrology model based on the relative saturated storage can be used safely to investigate the relation between hillslope geometry and hillslope stability.
• Teuling, A. J., Hupet, F., Uijlenhoet, R., & Troch, P. A. (2007). Climate variability effects on spatial soil moisture dynamics. GEOPHYSICAL RESEARCH LETTERS, 34(6).
• Teuling, A. J., Hupet, F., Uijlenhoet, R., & Troch, P. A. (2007). Climate variability effects on spatial soil moisture dynamics. Geophysical Research Letters, 34(6).
• Teuling, A. J., Uijlenhoet, R., Hurkmans, R., Merlin, O., Panciera, R., Walker, J. P., & Troch, P. A. (2007). Dry-end surface soil moisture variability during NAFE'06. Geophysical Research Letters, 34(17).
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2007). Interactions of breaking waves with a current over cut cells. Journal of Computational Physics, 223(2), 865-897.
  More info

  Abstract: By design of the external and internal wave-current generators, the objective of this paper is to extend our efficient Navier-Stokes solver [T. Li, P. Troch, J. De Rouck, Wave overtopping over a sea dike, J. Comput. Phys. 198 (2004) 686-726] for modelling of interactions between breaking waves and a current over a cut-cell grid, based on a dynamic subgrid-scale (SGS) model. This solver is constructed by a novel VOF finite volume approach, coupled with surface tension. When studying waves following a positive current, our external generator creates the combined inflow motions of waves and a current, which is viewed as one type of wavy inflow conditions. For cases of waves against strong currents, our internal generator describes the opposing current, by incorporating the source function to the continuity and momentum equations as a net driving force, acting on the fluid elements lying within the finite thickness source region. The outgoing waves downstream are dissipated with a breaking-type wave absorber placed in the tank extremity. Five test cases recommended are of distinctly different applications of interest, characterized by overtopping of following waves over sloping and vertical structures. Under the grid refinement effects, the results in 2D and 3D are in close agreement with the experimental data available in terms of the surface wave. Additionally, the performance of convergence in computations is also investigated, including full discussion for waves on beaches between 2D and 3D. By visualization of the motions that describe the physics of turbulence, it has been shown that our solver can capture most of the significant features in wave-current interactions varying with three different current speeds (positive, zero, negative). © 2006 Elsevier Inc. All rights reserved.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2007). Numerical simulation of motions of moving bodies in waves. Proceedings of the International Offshore and Polar Engineering Conference, 2125-2133.
  More info

  Abstract: In this paper, we develop a mass-force coupling model for simulation of the motion of a moving body in waves, based on our highly efficient Navier-Stokes solver (Li et al., 2004; 2006), named LVOF. LVOF is constructed by a novel VOF finite volume cut-cell approach, coupled with a dynamic subgrid-scale (SGS) model. By explicitly tracking the interface as a set of curves in 2D or a planar interface in 3D (where the location of the object in the grid is described with coefficients of the volume and area fractions), we capture the solid-liquid phase front over a fixed Cartesian grid without smearing the information at the particle-fluid interface. The rigid body distributed over the particle domain is treated as a fluid. Furthermore, the dynamic coupling between the particle and fluid phases is realized by adding mass and force terms into the continuity and momentum equations as a net driving force, acting on varying fluid elements. Grid refinement studies are performed for test problems involving the wedge entry and motion of a body prescribed in waves. Additionally, issue about the convergence performance is addressed. Under the prescribed entry velocity, we also concern water entry of a circular cylinder. Very encouragingly, the results agree well with measurements available. It is demonstrated that most of typical features in complex flow patterns can be captured in waves superimposed on the following currents, by using LVOF. Copyright © 2007 by The International Society of Offshore and Polar Engineers(ISOPE).
• Troch, P., Durcik, M., Seneviratne, S., Hirschi, M., Teuling, A., Hurkmans, R., & Hasan, S. (2007). New data sets to estimate terrestrial water storage change. Eos, 88(45), 469-470.
• Willems, K., Sanchez-Arcilla, A., Aguar, J. G., Rouck, J. D., Troch, P., & Bolaños, R. (2007). Extreme waves revisited. Proceedings of the Coastal Engineering Conference, 802-811.
  More info

  Abstract: An important difficulty in the field of maritime engineering is the probabilistic nature of wave drivers. To quantify the magnitude of forces that a structure will be exposed to in its lifetime, a maritime engineer needs to have a good understanding of the extreme climate of the region. By conducting extreme wave analyses on previously gathered wave data one can estimate design values, but there will always be uncertainty present. The objective of this paper is evaluating that uncertainty. More specifically, we will formulate conclusions about the uncertainty that lies in the model as well as the method that is used to conduct the analyses. But the latter is also influenced by regional particularities. In order to have a better view on those regional particularities, we conducted our investigation with data from two distinct maritime environments: the NW Mediterranean and the Southern North Sea. A last point of interest is the effect of the amount of the recorded data on the uncertainty within extreme wave analyses. We will do this by conducting extreme wave analyses on well-chosen datasets: developed with different selection methods, representing different time periods, having different sizes. It will therefore be necessary to establish storm databases for both regions and with different methods. Besides conducting non-directional and directional wave analyses, we also look into other storm characteristics. The results presented in this paper do not only give additional insights in the way to conduct extreme wave analyses, but will also provide more insight in the storm behaviour of both regions, the evolution of storm characteristics in the past two decades and its implications on the uncertainty in extreme wave analyses. © 2007 World Scientific Publishing Co. Pte. Ltd.
• Bogaart, P. W., & Troch, P. A. (2006). Curvature distribution within hillslopes and catchments and its effect on the hydrological response. Hydrology and Earth System Sciences, 10(6), 925-936.
  More info

  Abstract: Topographic convergence and divergence are first order controls on the hillslope and catchment hydrological response, as evidenced by similarity parameter analyses. Hydrological models often do not take convergence as measured by contour curvature directly into account; instead they use comparable measures like the topographic index, or the hillslope width function. This paper focuses on the question how hillslope width functions and contour curvature are related within the Plynlimon catchments, Wales. It is shown that the total width function of all hillslopes combined suggest that the catchments are divergent in overall shape, which is in contrast to the perception that catchments should be overall convergent. This so-called convergence paradox is explained by the effect of skewed curvature distributions and extreme curvatures near the channel network. The hillslope-storage Bossiness (hsB) model is used to asses the effect of within-hillslope convergence variability on the hydrological response. It is concluded that this effect is small, even when the soil saturation threshold is exceeded. Also described in this paper is a novel algorithm to compute flow path lengths on hillslopes towards the drainage network, using the multi-directional flow redistribution method.
• Doncker, L. D., Troch, P., Verhoeven, R., Bal, K., & Meire, P. (2006). Influence of aquatic plants on the flow resistance and the hydraulic capacity of vegetated rivers. Proceedings of the International Conference on Fluvial Hydraulics - River Flow 2006, 1, 593-602.
  More info

  Abstract: Vegetation growth drastically influences water levels and flow patterns in lowland rivers. Rise of the water level can have consequences for the surrounding areas and varying velocity patterns can influence the morphology of the river. The universities of Ghent and Antwerp are carrying out research in the river Aa, the Grote Kaliebeek and the Desselse Nete (Antwerp, Belgium) in order to better understand the natural phenomena involved and to come to a more accurate determination of the different parameters. Field measurements are carried out to collect data on discharge, stage and amount and variation of aquatic weed growth. The variation of the friction factor (Manning coefficient), influenced by the varying amount of vegetation, is determined as a function of time and distance. Following a seasonal cycle, flow resistance increases with plant growth in spring, reaches a maximum in early summer and then decreases slowly to the minimum in winter. Knowledge of the variation of the biomass in the time will lead to appropriate use of roughness coefficients in modelling surface flow in rivers. © 2006 Taylor & Francis Group.
• Hasan, S., Troch, P. A., Boll, J., & Kroner, C. (2006). Modeling the hydrological effect in local gravity at Moxa, Germany. Journal of Hydrometeorology, 7(3), 346-354.
  More info

  Abstract: A superconducting gravimeter has observed with high accuracy (to within a few nm s-2) and high frequency (1 Hz) the temporal variations in the earth's gravity field near Moxa, Germany, since 1999. Hourly gravity residuals are obtained by time averaging and correcting for earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals are significantly affected by hydrological processes (interception, infiltration, surface runoff, and subsurface redistribution) in the vicinity of the observatory. In this study time series analysis and distributed hydrological modeling techniques are applied to understand the effect of these hydrological processes on observed gravity residuals. It is shown that the short-term response of gravity residuals to medium- to high-rainfall events can be efficiently modeled by means of a linear transfer function. This transfer function exhibits an oscillatory behavior that indicates fast redistribution of stored water in the upper layers (interception store, root zone) of the catchment surrounding the instrument. The relation between groundwater storage and gravity residuals is less clear and varies according to the season. High positive correlation between groundwater and gravity exists during winter months when the freezing of the upper soil layers immobilizes water stored in the unsaturated zone of the catchment. To further explore the spatiotemporal dynamics of the relevant hydrological processes and their relation to observed gravity residuals, a GIS-based distributed hydrological model is applied for the Silberleite catchment. Driven by observed atmospheric forcings (precipitation and potential evapotranspiration), the model allows the authors to compute the variation of water storage in three different layers: the interception store, the snow cover store, and the soil moisture store. These water storage dynamics are then converted to predicted gravity variation at the location of the superconducting gravimeter and compared to observed gravity residuals. During most of the investigated period (January 2000 to January 2004) predictions are in good agreement with the observed patterns of gravity dynamics. However, during some winter months the distributed hydrological model fails to explain the observations, which supports the authors' conclusion that groundwater variability dominates the hydrological gravity signal in the winter. More hydrogeological research is needed to include groundwater dynamics in the hydrological model. © 2006 American Meteorological Society.
• Hilberts, A. G., & Troch, P. A. (2006). Comment on "influence of capillarity on a simple harmonic oscillating water table: Sand column experiments and modeling" by Nick Cartwright et al.. Water Resources Research, 42(11).
• Hilberts, A., & Troch, P. A. (2006). Comment on "influence of capillarity on a simple harmonic oscillating water table: Sand column experiments and modeling" by Nick Cartwright et al.. Water Resources Research, 42(11).
• Hurkmans, R., Paniconi, C., & Troch, P. A. (2006). Numerical assessment of a dynamical relaxation data assimilation scheme for a catchment hydrological model. Hydrological Processes, 20(3), 549-563.
  More info

  Abstract: A dynamical relaxation scheme for assimilating observation data into a three-dimensional Richards equation-based numerical model was presented in Paniconi et al. (2003. Advances in Water Resources 26: 161-178). The technique, known as Newtonian relaxation or nudging, relies on a forcing term to reduce the difference between computed and observed values of a state variable such as soil moisture content. The forcing term contains data quality and nudging influence factors, and, importantly, spatio-temporal weighting functions that determine the manner and extent of spreading of a state variable beyond its measurement points and times. In this paper, a series of numerical experiments is run for a small catchment in southern Belgium to investigate the performance of the nudging algorithm. In a first set of runs for a short (10-day) simulation period, the model's sensitivity to influence radii and forcing strength parameters is examined. Here, we find that prediction errors decrease and numerical cost increases for increasing values of the parameters, except for the vertical radius of influence, where intermediate values produced the lowest prediction errors. Based on a compromise between numerical and physical results for this 10-day experiment, 'optimal' values were selected for these parameters, and a second, much longer (8-month) set of simulations is used to explore the effect of the observation frequency on the quality of the assimilation. Here, it is found that prediction errors are lowest at an intermediate frequency, whereas serious numerical difficulties occur at a high frequency. As could be expected, computational costs are highest when frequent observations are assimilated. However, since CPU times increase only very slowly as more observation datasets are added, we can conclude that the nudging method is computationally efficient, albeit quiet sensitive in terms of numerical performance to its parameter settings, and thus requires further study to devise more robust formulations of the algorithm. Copyright © 2005 John Wiley & Sons, Ltd.
• Margulis, S. A., Wood, E. F., & Troch, P. A. (2006). The terrestrial water cycle: Modeling and data assimilation across catchment scales. Journal of Hydrometeorology, 7(3), 309-311.
• Rouck, J. D., Geeraerts, J., Troch, P., Kortenhaus, A., Pullen, T., & Franco, L. (2006). New results on scale effects for wave overtopping at coastal structures. International Conference on Coastlines, Structures and Breakwaters 2005: Harmonising Scale and Detail - Proceedings of the International Conference on Coastlines, Structures and Breakwaters 2005, 2006, 29-43.
  More info

  Abstract: It is proven that wave run up on rough slopes is underestimated in small scale model tests due to scale / model effects. Given this fact, the same effects are suspected to be present for wave overtopping. A thorough comparison between prototype measurements of wave overtopping at three different coastal structures and scale model tests of these structures has been performed. The present paper gives the results from this comparison and presents a procedure to determine whether scale effects can be present in a certain situation. The procedure allows to calculate the magnitude of the scale and wind effect that can be expected. Since a lot of designs are based on physical model tests, this procedure has a broad range of applicability and its importance should be stressed.
• Teuling, A. J., Andel, S. V., Troch, P. A., & Hoitink, A. J. (2006). Entropy and river meander planform. Proceedings of the International Conference on Fluvial Hydraulics - River Flow 2006, 2, 1137-1146.
  More info

  Abstract: Equilibrium meander bends shift downstream with a constant speed while maintaining a coherent form. Based on a dynamical description of flow in alluvial river bends and a kinematic description of continuous bank erosion, Parker et al. (1983) derived a class of equilibrium meander planform shapes known as Kinoshita curves. These equilibria were found to be unstable, which has lead to the common idealized view that meanders alternately elongate by gradual bend erosion and shorten due to cut-off, and do not reach a true equilibrium. It is herein argued that the extremely slow rate of change of near-equilibrium meanders in conjunction with neglected aspects such as time variation of the threshold of sediment motion can be the reason why most undisturbed meanders found in nature are in fact near-equilibrium. It is therefore worthwhile to further examine and describe equilibrium meanders, which is the subject of the present study. Starting from the hypothesis that for equilibrium meanders the variance of entropy production is minimized, most probable planform parameter values are derived that determine how fattening and skewing (parameterized by cf and cs, respectively) of an equilibrium meander depend on sinuosity. Sinuosity, in turn, is mainly externally controlled. It is shown how the hypothesis ofminimumvariance of entropy production practically boils down to the assumption ofminimization of channel morphology change rates, revealing the mechanistic interpretation of the theory. The validity of our hypothesis is elucidated by a comparison with twenty four meander reaches of various geographical locations, and by the fact that for arbitrary sinuosities a unique minimum for the variance of entropy production in the (cf, cs)-plane exists. © 2006 Taylor & Francis Group,.
• Teuling, A. J., Seneviratne, S. I., Williams, C., & Troch, P. A. (2006). Observed timescales of evapotranspiration response to soil moisture. Geophysical Research Letters, 33(23).
• Teuling, A. J., Uijlenhoet, R., Hupert, F., & Troch, P. A. (2006). Impact of plant water uptake strategy on soil moisture and evapotranspiration dynamics during drydown. Geophysical Research Letters, 33(3).
• Teuling, A. J., Uijlenhoet, R., Hupet, F., Loon, E. V., & Troch, P. A. (2006). Estimating spatial mean root-zone soil moisture from point-scale observations. Hydrology and Earth System Sciences, 10(5), 755-767.
  More info

  Abstract: Root zone soil moisture is a key variable in many land surface hydrology models. Often, however, there is a mismatch in the spatial scales at which models simulate soil moisture and at which soil moisture is observed. This complicates model validation. The increased availability of detailed datasets on space-time variability of root-zone soil moisture allows for a posteriori analysis of the uncertainties in the relation between point-scale observations and the spatial mean. In this paper we analyze three comprehensive datasets from three different regions. We identify different strategies to select observation sites. For instance, sites can be located randomly or according to the rank stability concept. For each strategy, we present methods to quantify the uncertainty that is associated with this strategy. In general there is a large correspondence between the different datasets with respect to the relative uncertainties for the different strategies. For all datasets, the uncertainty can be strongly reduced if some information is available that relates soil moisture content at that site to the spatial mean. However this works best if the space-time dynamics of the soil moisture field are known. Selection of the site closest to the spatial mean on a single random date only leads to minor reduction of the uncertainty with respect to the spatial mean over seasonal timescales. Since soil moisture variability is the result of a complex interaction between soil, vegetation, and landscape characteristics, the soil moisture field will be correlated with some of these characteristics. Using available information, we show that the correlation with leaf area index or a wetness coefficient alone is insufficient to predict if a site is representative for the spatial mean soil moisture content.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2006). On the study of wave-current-structure interactions in a numerical wave tank. Proceedings of the International Offshore and Polar Engineering Conference, 356-362.
  More info

  Abstract: With a wave-current generator designed in a numerical wave tank (NWT), we extended our highly efficient Navier-Stokes solver (Li et al., 2004a;b) for modelling of wave-current-structure interactions. This solver (named LVOF) is constructed by a novel VOF finite volume approach that incorporates surface tension, coupled with a dynamic subgrid-scale (SGS) turbulence model. The numerical generator located in the inflow boundary oscillates vertically the combined motions of waves and currents starting from its static stage, while the outgoing waves downstream are dissipated by a breaking-type absorber placed in the tank extremity (or a numerical damping zone). Test cases concern a combination of wave propagation, current, shoaling, reflection and breaking, when overtopping of waves over a seadike and seawall, including the study in the channel wave motions following and opposing a current. By using LVOF, our results demonstrate that most of typical features in the wave-induced motions can be captured in waves superimposed on the following (or opposing) currents. By comparison, the velocity profile and the wave train are in good agreement with measurements available. Copyright © 2006 by The International Society of Offshore and Polar Engineers.
• Van, B., Rouck, J. D., Troch, P., Geeraerts, J., & Frigaard, P. (2006). Discussion: Wave run-up on rubble breakwaters: Spectral effects. Proceedings of the Institution of Civil Engineers: Maritime Engineering, 159(3), 129-130.
• Wojcik, R., Troch, P. A., Stricker, H., Torfs, P., Wood, E., Su, H., & Su, Z. (2006). Mixtures of Gaussians for uncertainty description in bivariate latent heat flux proxies. JOURNAL OF HYDROMETEOROLOGY, 7(3), 330-345.
• Wójcik, R., Troch, P. A., Stricker, H., Torfs, P., Wood, E., Su, H., & Su, Z. (2006). Mixtures of Gaussians for uncertainty description in bivariate latent heat flux proxies. Journal of Hydrometeorology, 7(3), 330-346.
  More info

  Abstract: This paper proposes a new probabilistic approach for describing uncertainty in the ensembles of latent heat flux proxies. The proxies are obtained from hourly Bowen ratio and satellite-derived measurements, respectively, at several locations in the southern Great Plains region in the United States. The novelty of the presented approach is that the proxies are not considered separately, but as bivariate samples from an underlying probability density function. To describe the latter, the use of Gaussian mixture density models - a class of nonparametric, data-adaptive probability density functions - is proposed. In this way any subjective assumptions (e.g., Gaussianity) on the form of bivariate latent heat flux ensembles are avoided. This makes the estimated mixtures potentially useful in nonlinear interpolation and nonlinear probabilistic data assimilation of noisy latent heat flux measurements. The results in this study show that both of these applications are feasible through regionalization of estimated mixture densities. The regionalization scheme investigated here utilizes land cover and vegetation fraction as discriminatory variables. © 2006 American Meteorological Society.
• Berne, A., Uijlenhoet, R., & Troch, P. A. (2005). Similarity analysis of subsurface flow response of hillslopes with complex geometry. Water Resources Research, 41(9), 1-10.
  More info

  Abstract: [1] The matter of the efficient and parsimonious parameterization of hillslope subsurface flow remains an important issue in catchment hydrological studies (Brutsaert, 1995). Insights into the influence of the shape and hydraulic characteristics of hillslopes is required to further our understanding and our ability to model catchment hydrological processes. Recently, Troch et al. (2003) introduced the hillslope-storage Boussinesq (HSB) equation to describe subsurface flow and saturation along geometrically complex hillslopes. The HSB equation can be linearized and further reduced to an advection-diffusion equation for subsurface flow in hillslopes with constant bedrock slopes and exponential width functions. This paper presents a dimensional analysis of the latter equation in order to study the moments of the characteristic response function (CRF), corresponding to the free drainage of this type of hillslope. These moments, in a dimensionless form, can be expressed as functions of a similarity parameter, hereafter called the hillslope Péclet number, and a group of dimensionless numbers accounting for the effects of the boundary and initial conditions. The analytical expressions for the first four central CRF moments are derived for two types of initial conditions. The analysis of their respective influences shows that the hillslope Péclet number is an efficient similarity parameter to describe the hillslope subsurface flow response. Moreover, comparison between the CRF moments predicted by means of our similarity analysis and empirical moments derived from outflow measurements for different types of laboratory hillslopes shows good agreement. Copyright 2005 by the American Geophysical Union.
• Bouma, J. J., François, D., & Troch, P. (2005). Risk assessment and water management. Environmental Modelling and Software, 20(2), 141-151.
  More info

  Abstract: In order to implement water management in a sustainable way, the related decision-making processes have to take the ecological and socio-economic consequences into account. In The Netherlands, policy makers struggle with the question of how they can deal with flood risks. This paper presents some results of a research project sponsored by the Dutch Ministry of Water management in order to develop a risk assessment approach that assists decision-makers in dealing with flood risks. It shows that dealing with risk in decision-making related to water management manifests itself in different ways. One aspect is the incorporation of risk in the process of valuation of socio-economic effects. Another aspect is the incorporation of the valued socio-economic effects into the decision-making process. The paper shows that different attitudes towards risk determine to a large extent how the valued effects are assessed. This element has been widely discussed in the literature. The results are innovative in that they also show that risk attitudes and the understanding of the risk concept interfere with the outcome of the decision-making process in the field of water management. The paper provides an approach to how the concept of risk can be operationalized in different ways by decision-makers in dealing with flood risks. The approach is applied in two case studies. The results show that different institutional contexts impose different ways of dealing with risks which may significantly change over time (discount rates, risk attitudes, relevance of ecological effects, etc.). © 2004 Elsevier Ltd. All rights reserved.
• Hilberts, A. G., Troch, P. A., & Paniconi, C. (2005). Storage-dependent drainable porosity for complex hillslopes. Water Resources Research, 41(6), 1-13.
  More info

  Abstract: In hydraulic groundwater theory the parameter drainable porosity f (a storage coefficient that accounts for the effect of the unsaturated zone on water table dynamics) is usually treated as a constant. For shallow unconfined aquifers the value of this parameter, however, depends on the depth to the water table and the water retention characteristics of the soil. In this study an analytical expression for f as a function of water table depth is derived under the assumption of quasi-steady state hydraulic equilibrium, in this way accounting, in part, for the effects of the unsaturated zone on groundwater dynamics. The derived expression is implemented in the nonlinear hillslope-storage Boussinesq (HSB) model (Troch et al., 2003) to simulate the drainage response of complex hillslopes. The model's behavior is analyzed by comparison to (1) the HSB model with a constant value for f and (2) measurements of water tables and outflow hydrographs on a 6.0 x 2.5 x 0.5 m laboratory hillslope experiment. The comparison is conducted for a pure drainage case on two different hillslope shapes (linearly convergent and divergent) and for three different slope inclinations (5%, 10%, and 15%). Comparison 1 is run in an uncalibrated and a fully calibrated mode, and it enables us to evaluate the effect of a dynamic, state-dependent value for f on model output. Comparison 2 allows us to test the HSB model on several hillslope configurations and to analyze whether the concept of a storage-dependent/enhances the model performance. The comparison of the HSB models to the measurements from the laboratory hillslopes shows that it is possible to capture the general features of the outflow hydrograph during a drainage experiment using either one of the HSB models. Overall, the original (constant f) HSB model, with one fitting parameter more than the revised HSB model, shows a slightly better fit on the hydrographs when compared to the revised (variable f) HSB model. However, the peak outflow values (the first few minutes after initiation of the experiments) are better captured by the revised HSB model. The revised HSB model's performance in simulating water table movements is much more accurate than that of the original HSB model. The improved match of the revised HSB model to piezometric measurements is worth stressing because the ability to model water tables is a key attribute of the model, making it possible to investigate phenomena such as saturation excess runoff. Also noteworthy is the good match between the revised HSB model and the outflow measurements, without any calibration, for the divergent slopes. The changing values of the calibrated drainable porosity parameter for the original HSB model as different configurations are simulated (slope angle, plan shape, initial conditions), together with the ability of the revised HSB model to more accurately simulate water table dynamics, clearly demonstrates the importance of regarding drainable porosity as a dynamic, storage-dependent parameter. Copyright 2005 by the American Geophysical Union.
• Teuling, A. J., & Troch, P. A. (2005). Improved understanding of soil moisture variability dynamics. Geophysical Research Letters, 32(5), 1-4.
  More info

  Abstract: Different trends of soil moisture variability with mean moisture content have been reported from field observations. Here we explain these trends for three different data sets by showing how vegetation, soil and topography controls interact to either create or destroy spatial variance. Improved understanding of these processes is needed for the transformation of point-scale measurements and parameterizations to scales required for climate studies, operational weather forecasting, and large scale hydrological modeling. Copyright 2005 by the American Geophysical Union.
• Teuling, A. J., Uijlenhoet, R., & Troch, P. A. (2005). On bimodality in warm season soil moisture observations. Geophysical Research Letters, 32(13), 1-4.
  More info

  Abstract: It has recently been suggested that the bimodality in warm season soil moisture observations in Illinois is evidence of a soil moisture-precipitation feedback. Other studies however provide little evidence for a strong feedback in this region. Here we show that seasonality in the meteorological conditions in combination with the nonlinearity of the soil moisture response alone can induce this bimodality. The existence of preferred wet and dry soil moisture states may have implications for the understanding and modeling of soil moisture dynamics in mid-latitude regions. Copyright 2005 by the American Geophysical Union.
• Van, B., Rouck, J. D., Troch, P., Geeraerts, J., & Frigaard, P. (2005). Wave run-up on rubble breakwaters: Spectral effects. Proceedings of the Institution of Civil Engineers: Maritime Engineering, 158(2), 59-67.
  More info

  Abstract: Seven sets of data for wave run-up on a rubble mound breakwater were combined and re-analysed, with full-scale, large-scale and small-scale model test results being taken into account. The dimensionless wave run-up value Ru2%/Hm0 was considered, where Ru2% is the wave run-up height exceeded by 2% of the wave run-up events and Hm0 is the significant wave height. The wave run-up data sets were compared and a clear influence of the spectral shape, characterised by the spectral width parameter ε, on wave run-up was noticed: high values of ε correspond to high values of Ru2%/Hm0 and vice versa. Differences in wave run-up results between the various data sets could be explained by a difference in spectral width observed within these data sets. A multi-regression formula was fitted to all wave run-up data. The formula is valid for permeable rubble mound breakwaters covered with either grooved cubes or rip-rap with a slope steeper than 1 : 2, surging waves and a JONSWAP-type wave spectrum.
• Wood, E. F., Boll, J., Bogaart, P., & Troch, P. (2005). The need for a virtual hydrologic laboratory for PUB. IAHS-AISH Publication, 189-203.
• Wood, E. F., Boll, J., Bogaart, P., & Troch, P. (2005). The need for a virtual hydrologic laboratory for PUB. Predictions in Ungauged Basins: International Perspectives on the State of the Art and Pathways Forward, 301, 189-203.
• Berne, A., Uijlenhoet, R., Troch, P., & Paniconi, C. (2004). Travel time distributions of subsurface flow along complex hillslopes with exponential width functions. Developments in Water Science, 55(PART 2), 1465-1477.
  More info

  Abstract: Recently, Troch et al. [10] introduced the hillslope-storage Boussinesq (hsB) equation to describe subsurface flow and saturation along complex hillslopes. They demonstrated that numerical solutions of the hsB equation account explicitly for plan shape of the hillslope, by introducing the hillslope width function, and for profile curvature through bedrock angle and the hillslope soil depth function (see also Paniconi et al. [7] and Hilberts et al. [4]). This paper presents an analytical solution of the linearized hsB equation applicable to hillslopes with constant bedrock slope and exponential width functions. Then, the first four moments of the impulse response function (travel time distribution) of such hillslopes are derived using the Laplace transform of the partial differential equation describing the groundwater flow. These moments are explicitly related to the hydraulic (porosity, conductivity) and geometric (bedrock slope, width function, and soil depth) parameters of a hillslope. The zeroth moment can obviously be interpreted as the total outflow volume, and the (normalized) first moment as the mean response time of the hillslope. The second, third, and fourth moments have interpretations in terms of the relative width, asymmetry, and peakedness, respectively, of the hydrograph. The paper examines the effect of the geometric properties of hillslopes on the travel time distribution in a dimensionless context. © 2004 Elsevier B.V.
• Hilberts, A. G., Loon, E. V., Troch, P. A., & Paniconi, C. (2004). The hillslope-storage Boussinesq model for non-constant bedrock slope. Journal of Hydrology, 291(3-4), 160-173.
  More info

  Abstract: In this study the recently introduced hillslope-storage Boussinesq (hsB) model is cast in a generalized formulation enabling the model to handle non-constant bedrock slopes (i.e. bedrock profile curvature). This generalization extends the analysis of hydrological behavior to hillslopes of arbitrary geometrical shape, including hillslopes having curved profile shapes. The generalized hsB model performance for a free drainage scenario is evaluated by comparison to a full three-dimensional Richards equation (RE) based model. The model results are presented in the form of dimensionless storage profiles and dimensionless outflow hydrographs. In addition, comparison of both models to a storage based kinematic wave (KW) model enables us to assess the relative importance of diffusion processes for different hillslope shapes, and to analyze the influence of profile curvature on storage and flow patterns specifically. The comparison setup consists of a set of nine gentle (5% bedrock slope) and nine steep (30% bedrock slope) hillslopes of varying plan shape and profile curvature. Interpretation of the results shows that for highly conductive soils the simulated storage profiles and outflow hydrographs of the generalized hsB model and RE model match remarkably for 5% bedrock slope and for all plan and profile curvatures. The match is slightly poorer on average for 30% bedrock slope, in particular, on divergently shaped hillslopes. In the assessment of the influence of hydraulic diffusion, we find good agreement in simulation results for the KW model compared to results from the generalized hsB model and the RE model for steep divergent and uniform hillslopes, due to a relatively low ratio between water table gradient and bedrock slope compared to convergent or gentle hillslopes. Overall, we demonstrate that, in addition to bedrock slope, hillslope shape as represented by plan and profile curvature is an important control on subsurface flow response. © 2004 Elsevier B.V. All rights reserved.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2004). Large eddy simulation of wave overtopping on nonuniform cartesian cut-cell grids. Proceedings of the International Offshore and Polar Engineering Conference, 276-284.
  More info

  Abstract: Overtopping of water waves over the crest of vertical and sloping coastal structures is simulated with large-eddy simulation (LES) in this paper. The computations are conducted in a numerical wave tank, based on our recently developed solver. It involves a time-implicit cell-staggered approximately-factored volume-of-fluid (VOF) finite volume (FV) approach on a nonuniform Cartesian cut-cell grid. Additionally, the Godunov-type high-order up-wind schemes are introduced for discretization of the convective fluxes, while the coupling of the pressure with the velocity is realized by a projection method. A static Smagorinsky model and dynamic one are used for description of the subgrid-scale (SGS) stress. The surface tension effects are considered as a body force according to the continuous surface force manner. When flows are driven by a wave generator located at the inlet, the results for regular and irregular waves indicate that the LES technique predicts most of the significant features of the breaking waves during overtopping process. By comparison, computations agree well with measurements available under grid refinements. Copyright © 2004 by The International Society of Offshore and Polar Engineers.
• Tingqiu, L. i., Troch, P., & Rouck, J. D. (2004). Wave overtopping over a sea dike. Journal of Computational Physics, 198(2), 686-726.
  More info

  Abstract: This paper describes a solver on the simulation of overtopping of water waves over sloping and vertical structures in a numerical wave tank (NWT). It involves a time-implicit cell-staggered approximately factored VOF finite volume (FV) approach for solution of unsteady incompressible Navier-Stokes (NS) equations with a free surface on nonuniform Cartesian cut-cell grids. The Godunov-type high-order upwind schemes are introduced for discretization of the convective fluxes, while the coupling of the pressure with the velocity is realized by a projection method. The effects of turbulence are incorporated with a subgrid-scale (SGS) model. A novel VOF solver is proposed for the capture of a free surface undergoing severe topological deformation related with breaking waves. Only an approximation for the free-surface boundary conditions neglects the viscous stress but surface tension is modelled as a body force. A blend of second- and fourth-order artificial damping terms is designed for enhancement of the numerical stability. Additionally, the cut-cell techniques are utilized for handling an arbitrary geometry, and an absorbing-generating boundary condition for a wave generator is applied. The calculated results are represented in terms of the surface elevation versus time at certain locations and the velocity fields created by regular and irregular waves. Furthermore, the convergence behavior, the grid refinement effects, the study of different SGS models, the surface tension and Reynolds number effects and the role of a turbulence model under breaking waves are discussed, including a comparison with measurements available. © 2004 Elsevier Inc. All rights reserved.
• Troch, P. A., H., A., & G., A. (2004). Analytical solution of the linearized hillslope-storage Boussinesq equation for exponential hillslope width functions. Water Resources Research, 40(8), W086011-W086016.
  More info

  Abstract: This technical note presents an analytical solution to the linearized hillslope-storage Boussinesq equation for subsurface flow along complex hillslopes with exponential width functions and discusses the application of analytical solutions to storage-based subsurface flow equations in catchment studies.
• Troch, P. A., Van, L. A., & Hilberts, A. (2004). Analytical solution of the linearized hillslope-storage Boussinesq equation for exponential hillslope width functions. Water Resources Research, 40(8), W086011-W086016.
• Troch, P., Geeraerts, J., Van, B., Rouck, J. D., Damme, L. V., Allsop, W., & Franco, L. (2004). Full-scale wave-overtopping measurements on the Zeebrugge rubble mound breakwater. Coastal Engineering, 51(7), 609-628.
  More info

  Abstract: Field measurements of wave overtopping over a rubble mound breakwater have been carried out at Zeebrugge, Belgium, during the period 1999-2003. The overtopping volumes of water are collected in an overtopping tank located on the breakwater crest behind the access road. A short side of the tank is made of a weir, allowing the collected water to flow out continuously, and allowing measurements to be made for long duration. Calculation of the inflow discharge is based on the outflow discharge over the weir and the volume in the tank. This calculation requires an accurate measurement of the water depth inside the tank. The water depth is measured indirectly using a pressure sensor near the bottom. The measurement setup for wave overtopping at the breakwater is described in detail. Eight-wave records with wave propagation normal to the breakwater have been used in the analysis of the field data. Wave heights range between 2.6 and 3.9 m (i.e., up to 63% of the design wave height) for wave records with a typical duration of 1-2 h. The measured average overtopping rate q has been determined for all records using three methods (q
• Jimmy, G., Peter, T., Julien, R. D., Luc, D. V., & Tim, P. (2003). Hazards resulting from wave overtopping full scale measurements. Coastal Structures 2003 - Proceedings of the Conference, 481-493.
  More info

  Abstract: A fully operational system to measure hazards resulting from waves overtopping the Zeebrugge rubble mound breakwater is discussed. The measurement site and the specific set-up used for wave overtopping measurements is also presented. The available link between measured forces and velocities on the one hand side and both overtopping volume/rates and incident wave conditions on the other side has been shown. It is suggested that more linking between measured forces and measured overtopping volumes/rates is necessary to give guidance on tolerable overtopping rates-volumes.
• Montaldo, N., Toninelli, V., Albertson, J. D., Mancini, M., & Troch, P. A. (2003). The effect of background hydrometeorological conditions on the sensitivity of evapotranspiration to model parameters: Analysis with measurements from an Italian alpine catchment. Hydrology and Earth System Sciences, 7(6), 848-861.
  More info

  Abstract: Recent developments have made land-surface models (LSMs) more complex through the inclusion of more processes and controlling variables, increasing numbers of parameters and uncertainty in their estimates. To overcome these uncertainties, prior to applying a distributed LSM over the whole Toce basin (Italian Alps), a field campaign was carried out at an experimental plot within the basin before exploring the skill and parameter importance (sensitivity) using the TOPLATS model, an existing LSM. In the summer and autumn of 1999, which included both wet (atmosphere controlled) and dry (soil controlled) periods, actual evapotranspiration estimates were performed using Bowen ratio and, for a short period, eddy correlation methods. Measurements performed with the two methods are in good agreement. The calibrated LSM predicts actual evapotranspiration quite well over the whole observation period. A sensitivity analysis of the evapotranspiration to model parameters was performed through the global multivariate technique during both wet and dry periods of the campaign,. This approach studies the influence of each parameter without conditioning on certain values of the other variables. Hence, all parameters are varied simultaneously using, for instance, a uniform sampling strategy through a Monte Carlo simulation framework. The evapotranspiration is highly sensitive to the soil parameters, especially during wet periods. However, the evapotranspiration is also sensitive to some vegetation parameters and, during dry periods, wilting point is the most critical for evapotranspiration predictions. This result confirms the importance of correct representation of vegetation properties which, in water-limited conditions, control evapotranspiration. © EGU.
• Paniconi, C., Troch, P. A., Emiel, E., & G., A. (2003). Hillslope-storage Boussinesq model for subsurface flow and variable source areas along complex hillslopes: 2. Intercomparison with a three-dimensional Richards equation model. Water Resources Research, 39(11), SBH41-SBH413.
  More info

  Abstract: The Boussinesq equation for subsurface flow in an idealized sloping aquifer of unit width has recently been extended to hillslopes of arbitrary geometry by incorporating the hillslope width function w(x) into the governing equation, where x is the flow distance along the length of the hillslope [Troch et al., 2003]. Introduction of a source/sink term N allows simulation of storm-interstorm sequences in addition to drainage processes, while a function Sc(x) representing the maximum subsurface water storage can be used to account for surface saturation response in variable source areas activated by the saturation excess mechanism of runoff generation. The model can thus simulate subsurface flow and storage dynamics for nonidealized (more realistic) hillslope configurations. In this paper we assess the behavior of this relatively simple, one-dimensional model in a series of intercomparison tests with a fully three-dimensional Richards equation model. Special attention is given to the discretization and setup of the boundary and initial conditions for seven representative hillslopes of uniform, convergent, and divergent plan shape. Drainage and recharge experiments are conducted on these hillslopes for both gentle (5%) and steep (30%) bedrock slope angles. The treatment and influence of the drainable porosity parameter are also considered, and for the uniform (idealized) hillslope case the impact of the unsaturated zone is examined by running simulations for different capillary fringe heights. In general terms, the intercomparison results show that the hillslope-storage Boussinesq model is able to capture the broad shapes of the storage and outflow profiles for all of the hillslope configurations. In specific terms, agreement with the Richards equation results varies according to the scenario being simulated. The best matches in outflow hydrographs were obtained for the drainage experiments, suggesting a greater influence of the unsaturated zone under recharge conditions due to transmission of water throughout the hillslope. In the spatiotemporal water table response a better match was observed for convergent than divergent hillslopes, and the bedrock slope angle was not found to greatly influence the quality of the agreement between the two models. On the basis of the intercomparison experiments we make some suggestions for further development and testing of the hillslope-storage model.
• Paniconi, C., Troch, P. A., Van, L. E., & Hilberts, A. (2003). Hillslope-storage Boussinesq model for subsurface flow and variable source areas along complex hillslopes: 2. Intercomparison with a three-dimensional Richards equation model. Water Resources Research, 39(11), SBH41-SBH413.
• Rouck, J. D., Van, B., Geeraerts, J., Troch, P., Damme, L. V., Kortenhaus, A., & Medina, J. (2003). Full scale wave overtopping measurements. Coastal Structures 2003 - Proceedings of the Conference, 494-506.
  More info

  Abstract: The full scale infrastructure to measure wave overtopping at the Zeebrugge rubble mound breakwater is discussed. The measurement site and the specific set-up used for wave overtopping measurements is also described. Waveovertopping has been measured successfully at full scale, at the Zeebrugge breakwater during eight storm events. Prototype average overtopping rates from all eight recorded storms are also found within the 95% confidence interval of the prediction formula by van der Meer.
• Schuurmans, J. M., Troch, P. A., Veldhuizen, A. A., Bastiaanssen, W. G., & Bierkens, M. F. (2003). Assimilation of remotely sensed latent heat flux in a distributed hydrological model. Advances in Water Resources, 26(2), 151-159.
  More info

  Abstract: This paper addresses the question of whether remotely sensed latent heat flux estimates over a catchment can be used to improve distributed hydrological model water balance computations by the process of data assimilation. The data used is a series of NOAA- NOAAAVHRR AVHRR satellite images for the Drentse Aa catchment in the Netherlands for the year 1995. These 1 × 1 km resolution images are converted into latent heat flux estimates using SEBAL (Surface Energy Balance Algorithm for Land [J Hydrol 2000;229:87]). The physically-based distributed model SIMGRO (SIM SIMulation of GRO GROundwater flow and surface water levels [J Hydrol 1997;192:158]) is used to compute the water balance of the Drentse Aa catchment for that same year. Comparison between model-derived and remotely sensed area-averaged evapotranspiration estimates show good agreement, but spatial analysis of the model latent heat flux estimates indicate systematic underestimation in areas with higher elevation. A constant gain Kalman filter data assimilation algorithm is used to correct the internal state variables of the distributed model whenever remotely sensed latent heat flux estimates are available. It was found that the spatial distribution of model latent heat flux estimates in areas with higher elevation were improved through data assimilation. © 2002 Elsevier Science Ltd. All rights reserved.
• Troch, P. A., Paniconi, C., & Emiel, E. (2003). Hillslope-storage Boussinesq model for subsurface flow and variable source areas along complex hillslopes: 1. Formulation and characteristic response. Water Resources Research, 39(11), SBH31-SBH312.
  More info

  Abstract: Hillslope response to rainfall remains one of the central problems of catchment hydrology. Flow processes in a one-dimensional sloping aquifer can be described by Boussinesq's hydraulic groundwater theory. Most hillslopes, however, have complex three-dimensional shapes that are characterized by their plan shape, profile curvature of surface and bedrock, and the soil depth. Field studies and numerical simulation have shown that these attributes are the most significant topographic controls on subsurface flow and saturation along hillslopes. In this paper the Boussinesq equation is reformulated in terms of soil water storage rather than water table height. The continuity and Darcy equations formulated in terms of storage along the hillslope lead to the hillslope-storage Boussinesq (HSB) equation for subsurface flow. Solutions of the HSB equation account explicitly for plan shape of the hillslope by introducing the hillslope width function and for profile curvature through the bedrock slope angle and the hillslope soil depth function. We investigate the behavior of the HSB model for different hillslope types (uniform, convergent, and divergent) and different slope angles under free drainage conditions after partial initial saturation (drainage scenario) and under constant rainfall recharge conditions (recharge scenario). The HSB equation is solved by means of numerical integration of the partial differential equation. We find that convergent hillslopes drain much more slowly compared to divergent hillslopes. The accumulation of moisture storage near the outlet of convergent hillslopes results in bell-shaped hydrographs. In contrast, the fast draining divergent hillslopes produce highly peaked hydrographs. In order to investigate the relative importance of the different terms in the HSB equation, several simplified nonlinear and linearized versions are derived, for instance, by recognizing that the width function of a hillslope generally shows smooth transition along the flow direction or by introducing a fitting parameter to account for average storage along the hillslope. The dynamic response of these reduced versions of the HSB equation under free drainage conditions depend strongly on hillslope shape and bedrock slope angle. For flat slopes (of the order of 5%), only the simplified nonlinear HSB equation is able to capture the dynamics of subsurface flow along complex hillslopes. In contrast, for steep slopes (of the order of 30%), we see that all the reduced versions show very similar results compared to the full version. It can be concluded that the complex derivative terms of width with respect to flow distance play a less dominant role with increasing slope angle. Comparison with the hillslope-storage kinematic wave model of Troch et al. [2002] shows that the diffusive drainage terms of the HSB model become less important for the fast draining divergent hillslopes. These results have important implications for the use of simplified versions of the HSB equation in landscapes and for the development of appropriate analytical solutions for subsurface flow along complex hillslopes.
• Troch, P., Tingqiu, L. i., Rouck, J. D., & Ingram, D. (2003). Wave Interaction with a Sea Dike Using a VOF Finite-Volume Method. Proceedings of the International Offshore and Polar Engineering Conference, 1670-1677.
  More info

  Abstract: This paper represents a solver for numerical simulation of breaking waves, developed at Ghent University using an implicit cell-staggered VOF finite volume approach. The mathematical model is based on unsteady incompressible Navier-Stokes (NS) equations with a free surface. A flux-difference splitting approach with the MUSCL type (or the ENO scheme) and a central-difference scheme are applied for evaluation of the inviscid and viscous fluxes, respectively. A projection method is involved for coupling of the pressure and the velocity. A free surface is tracked with the VOF method, in which the approximate dynamic boundary conditions are implemented. In addition, second- and fourth-order artificial damping terms are introduced to the velocity normal to the cell face. A Sommerfeld radiation condition is implemented at the open boundary to dissipate the energy of outgoing waves. More-over, cut-cell techniques are utilized for treatment of an arbitary geometry. The solver can capture many physical phenomena during the interaction of waves with a dike, when a wave run-up and overtopping over an impermeable sea dike are performed in a numerical wave tank.
• Loon, E. V., & Troch, P. A. (2002). Tiknohov regularization as a tool for assimilating soil moisture data in distributed hydrological models. Hydrological Processes, 16(2), 531-556.
  More info

  Abstract: Discharge, water table depth, and soil moisture content have been observed at a high spatial and temporal resolution in a 44 ha catchment in Costa Rica over a period of 5 months. On the basis of the observations in the first 3 months (period A), two distinct soil moisture models are identified and calibrated: a linear stochastic time-varying state-space model, and a geo-statistical model. Both models are defined at various spatial and temporal resolutions. For the subsequent period of 2 months (period B), four different ways to predict the soil moisture dynamics in the catchment are compared: (1) the application of the dynamic models in open-loop form; (2) a re-calibration of the dynamic models with soil moisture data in period B, and subsequent prediction in open-loop form; (3) prediction with the geostatistical models, using the soil moisture data in period B; (4) prediction by combining the outcomes of (1) and (3) via generalized cross-validation. The last method, which is a form of data assimilation, compares favourably with the three alternatives. Over a range of resolutions, the predictions by data assimilation have overall uncertainties that are approximately half that of the other prediction methods and have a favourable error structure (i.e. close to Gaussian) over space as well as time. In addition, data assimilation gives optimal predictions at finer resolutions compared with the other methods. Compared with prediction with the models in open-loop form, both re-calibration with soil moisture observations and data assimilation result in enhanced discharge predictions, whereas the prediction of ground water depths is not improved. Copyright © 2002 John Wiley and Sons, Ltd.
• Pauwels, V., Hoeben, R., Verhoest, N., De, T. F., & Troch, P. A. (2002). Improvement of TOPLATS-based discharge predictions through assimilation of ERS-based remotely sensed soil moisture values. Hydrological Processes, 16(5), 995-1013.
• R., V., Hoeben, R., E., N., P., F., & Troch, P. A. (2002). Improvement of TOPLATS-based discharge predictions through assimilation of ERS-based remotely sensed soil moisture values. Hydrological Processes, 16(5), 995-1013.
  More info

  Abstract: In this paper, we investigate the possibility to improve discharge predictions from a lumped hydrological model through assimilation of remotely sensed soil moisture values. Therefore, an algorithm to estimate surface soil moisture values through active microwave remote sensing is developed, bypassing the need to collect in situ ground parameters. The algorithm to estimate soil moisture by use of radar data combines a physically based and an empirical backscatter model. This method estimates effective soil roughness parameters, and good estimates of surface soil moisture are provided for bare soils. These remotely sensed soil moisture values over bare soils are then assimilated into a hydrological model using the statistical correction method. The results suggest that it is possible to determine soil moisture values over bare soils from remote sensing observations without the need to collect ground truth data, and that there is potential to improve model-based discharge predictions through assimilation of these remotely sensed soil moisture values. Copyright © 2002 John Wiley & Sons, Ltd.
• Troch, P., Loon, E. V., & Hilberts, A. (2002). Analytical solutions to a hillslope-storage kinematic wave equation for subsurface flow. Advances in Water Resources, 25(6), 637-649.
  More info

  Abstract: Hillslope response has traditionally been studied by means of the hydraulic groundwater theory. Subsurface flow from a one-dimensional hillslope with a sloping aquifer can be described by the Boussinesq equation [Mem. Acad. Sci. Inst. Fr. 23 (1) (1877) 252-260]. Analytical solutions to Boussinesq's equation are very useful to understand the dynamics of subsurface flow processes along a hillslope. In order to extend our understanding of hillslope functioning, however, simple models that nonetheless account for the three-dimensional soil mantle in which the flow processes take place are needed. This three-dimensional soil mantle can be described by its plan shape and by the profile curvatures of terrain and bedrock. This plan shape and profile curvature are dominant topographic controls on flow processes along hillslopes. Fan and Bras [Water Resour. Res. 34 (4) (1998) 921-927] proposed a method to map the three-dimensional soil mantle into a one-dimensional storage capacity function. Continuity and a kinematic form of Darcy's law lead to quasi-linear wave equations for subsurface flow solvable with the method of characteristics. Adopting a power function of the form proposed by Stefano et al. [Water Resour. Res. 36 (2) (2000) 607-617] to describe the bedrock slope, we derive more general solutions to the hillslope-storage kinematic wave equation for subsurface flow, applicable to a wide range of complex hillslopes. Characteristics drainage response functions for nine distinct hillslope types are computed. These nine hillslope types are obtained by combining three plan curvatures (converging, uniform, diverging) with three bedrock profile curvatures (concave, straight, convex). We demonstrate that these nine hillslopes show quite different dynamic behaviour during free drainage and rainfall recharge events. © 2002 Elsevier Science Ltd. All rights reserved.
• Troch, P., Rouck, J. D., & Schüttrumpf, H. (2002). Numerical simulation of wave overtopping over a smooth impermeable sea dike. Advances in Fluid Mechanics, 32, 715-724.
  More info

  Abstract: Numerical simulations of wave overtopping over a smooth impermeable sea dike are carried out using VOFbreak2, a numerical model that solves the unsteady, incompressible, Navier-Stokes equations. The results from the simulations are compared with physical model data. Good agreement is obtained for the average overtopping rates. Results are very sensitive to the choice of the computational grid. More research is required on simulation of wave breaking on the dike slope and the flow in a thin layer over the dike crest.
• Van, L. E., & Troch, P. A. (2002). Tiknohov regularization as a tool for assimilating soil moisture data in distributed hydrological models. Hydrological Processes, 16(2), 531-556.
• Verhoest, N. E., Pauwels, V. R., Troch, P. A., & P., F. (2002). Analytical solution for transient water table heights and outflows from inclined ditch-drained terrains. Journal of Irrigation and Drainage Engineering, 128(6), 358-364.
  More info

  Abstract: This paper presents two analytical solutions of the linearized Boussinesq equation for an inclined aquifer, drained by ditches, subjected to a constant recharge rate. These solutions are based on different initial conditions. First, the transient solution is obtained for an initially fully saturated aquifer. Then, an analytical expression is derived for the steady state solution by allowing time to approach infinity. As this solution represents the groundwater table shape more realistically, this water table profile is used as an initial condition in the derivation of the second analytical solution for the groundwater table height, and the in- and outflow into the ditches. The solutions allow the calculation of the transient behavior of the groundwater table, and its outflow, due to changing percolation rates or water level heights in both ditches.
• Loon, E. E., & Troch, P. A. (2001). Directives for 4-D soil moisture data assimilation in hydrological modelling. IAHS-AISH Publication, 257-268.
• Loon, E. v., & Troch, P. A. (2001). Directives for 4-D soil moisture data assimilation in hydrological modelling. IAHS-AISH Publication, 257-268.
  More info

  Abstract: Data assimilation is a procedure to provide time-dependent spatially-distributed estimates of a dynamic system using observations from various sources and with various physical constraints in an efficient way. Mathematically, it can be seen as a state estimation procedure. The spatio-temporal prediction of soil moisture is pre-eminently a problem that can be dealt with by data assimilation techniques. Even though there is considerable literature on data assimilation in the environmental sciences, the application to soil moisture estimation is still new. To date only the problem of integrating remotely sensed data or field-observations over a small area with a one-dimensional soil moisture model of the root zone has been studied. In all cases the assimilation technique comprises simplifications or variants of the weak-constraint variational technique (equivalent to the Kalman smoother). Problems involving more spatial dimensions and more diverse information sources have not yet been dealt with. This is partly because the dimensionality of the problem prohibits a straightforward extension of the common algorithms, i.e. new data assimilation algorithms need to be developed. The lack of appropriate data sets and regularization tools is also a serious impediment. As a first step towards applying soil moisture data assimilation to problems of a higher dimension, this study outlines the desirable structure of 4-D hydrological data assimilation algorithms, and discusses the consequences for data handling and the specification of hydrological models.
• Western, A., Sadek, T., Wang, L., Grayson, R., Turral, H., & Troch, P. (2001). Is SAR capable of mapping small-scale spatial patterns of soil moisture?. International Geoscience and Remote Sensing Symposium (IGARSS), 1, 40-42.
  More info

  Abstract: We assess the potential for measuring spatial patterns of soil moisture using SAR at spatial resolutions down to 15m. Highly detailed ground data on soil moisture and dielectric constant were collected in the 10.5 ha Tarrawarra experimental catchment in south-eastern Australia. C-band SAR measurements by ERS-1, ERS-2 and AirSAR provided no useful information on the spatial moisture pattern. Empirical comparisons suggest that L and P-band AirSAR data contain useful information on the soil moisture pattern, but this could not be extracted using a semi-empirical inversion algorithm. The spatial average moisture was successfully obtained from the L-band AirSAR data.
• E., N., & Troch, P. A. (2000). Some analytical solutions of the linearized Boussinesq equation with recharge for a sloping aquifer. Water Resources Research, 36(3), 793-800.
  More info

  Abstract: Subsurface flow from a hillslope can be described by the hydraulic groundwater theory as formulated by the Boussinesq equation. Several attempts have been made to solve this partial differential equation, and exact solutions have been found for specific situations. In the case of a sloping aquifer, Brutsaert [1994] suggested linearizing the equation to calculate the unit response of the hillslope. In this paper we first apply the work of Brutsaert by assuming a constant recharge to the groundwater table. The solution describes the groundwater table levels and the outflow in function of time. Then, an analytical expression is derived for the steady state solution by allowing time to approach infinity. This steady state water table is used as an initial condition to derive another analytical solution of the Boussinesq equation. This can then be used in a quasi steady state approach to compute outflow under changing recharge conditions.
• Herpe, Y. V., & Troch, P. A. (2000). Spatial and temporal variations in surface water nitrate concentrations in a mixed land use catchment under humid temperate climatic conditions. Hydrological Processes, 14(14), 2439-2455.
  More info

  Abstract: Streamwater nitrate (NO3-) concentrations along the main stream and at the outlet of several subcatchments within the 114.3 km2 Zwalm watershed in Flanders, Belgium, have been monitored regularly since 1991. Land use within the Zwalm catchment is predominantly agricultural, with forested regions in the south and urban concentrations in the north-east of the catchment. Streamwater NO3- concentrations increased with increases in stream discharge rates, but in general, discharge rate explained only about 30% of the variation in NO3- concentrations. The low R2 values were attributed to the observed anticlockwise hysteresis in the NO3- concentration-discharge relationship and to differences in NO3- concentrations between both seasonal flow and various flow regimes, with winter flow explaining 51% of the variation in NO3- concentrations, whereas summer flow explained only 28% of the variation. A hypothesis was formulated in which flow regime accounts for the seasonal variation in NO3- export, postulating that the catchment seasonally alternates between two hydrological stages. The first stage occurs during wet winter periods, when the catchment drains as a single source area, whereas the second stage occurs during dry summer periods, when the groundwater store disconnects into separate subcatchments. This causes NO3- concentration peaks to be more delayed during summer storm events compared with winter storm events. Regarding flow regimes, differences between high and low flow conditions and between increasing and stable/decreasing flow eere not as pronounced a differences between seasons. In contrast to the estimation of NO3- concentrations, discharge was a strong predictor (R2 = 0.71) of the NO3- flux within the tributaries of the Zwalm catchment. The NO3- concentrations in the main stream increased with decreasing elevation, whereas the seasonal concentration patterns along the main channel were similar to those observed at the outlet. NO3- concentrations varied considerably among catchments and showed a high variability over time, although in general, the variation in NO3- concentration was higher between catchments than within catchments. The impact of land use is clearly reflected in the streamwater NO3- concentrations, although NO3- concentration patterns were also affected by topography and, to a lesser extent, by soil type. A gradual increase in NO3- concentrations at the outlet of the Zwalm catchment could be observed throughout the 1991 - 1998 study period, providing evidence for the general trends of increase in Flanders, which are attributed to the intensification of agricultural activities. Copyright (C) 2000 John Wiley and Sons, Ltd.
• Hoeben, R., & Troch, P. A. (2000). Assimilation of active microwave measurements for soil moisture profile retrieval under laboratory conditions. International Geoscience and Remote Sensing Symposium (IGARSS), 3, 1271-1273.
  More info

  Abstract: We discuss the potential of retrieving information on the soil moisture profile from measurements of the surface soil moisture content through active microwave observations. Here we use active microwave observations of the surface soil moisture content in a data assimilation framework to show that this allows the retrieval of the entire soil moisture profile. The data assimilation procedure demonstrated is based on the Kalman filter technique. Kalman filtering allows reconstruction of the state vector when at least part of the state variables are observed regularly. The dynamic model of the system used here is based on the 1D Richards equation. The observation equation is based on the Integral Equation Model and is used to link the radar observations to surface soil moisture content. Recently, reported about laboratory experiments investigating the use of active microwave observations to estimate surface soil moisture content. We apply the data assimilation scheme to the radar measurements of these experiments to retrieve the entire soil moisture profile in the soil sample used, and compare these results with the soil moisture profile measurements (using TDR). It is shown that with a limited number of radar measurements accurate retrieval of the entire soil moisture profile is possible.
• Hoeben, R., & Troch, P. A. (2000). Assimilation of active microwave observation data for soil moisture profile estimation. Water Resources Research, 36(10), 2805-2819.
  More info

  Abstract: This paper discusses the potential of retrieving information about the soil moisture profile from measurements of the surface soil moisture content through active microwave observations of the Earth. Recently, Mancini et al. [1999] have shown through laboratory experiments that the volumetric moisture content of the first few centimeters of a bare soil can be determined within 5% vol accuracy by means of C and L band active microwave observations and inverse modeling. Here we use active microwave observations of the surface soil moisture content in a data assimilation framework to show that this allows the retrieval of the root zone soil moisture profile. The data assimilation procedure developed is based on the Kalman filter technique. Kalman filtering allows reconstruction of the state vector of a system when this system is represented by a dynamic model and when at least part of the state variables are observed regularly. The dynamic model of the system used here is based on the one-dimensional Richards equation. The observation equation is based on the Integral Equation Model [Fung et al., 1992; Fung, 1994] and is used to link the radar observations to surface soil moisture content. It is shown that even in the presence of model and observation noise and infrequent observations, accurate retrieval of the entire moisture profile is possible for a bare soil.
• Paniconi, C., Troch, P. A., Mancini, M., & Dessena, M. A. (2000). Soil moisture mapping from ASAR imagery for the Flumendosa and Meuse River basins. European Space Agency, (Special Publication) ESA SP, 1150-1160.
  More info

  Abstract: The soil moisture mapping and the spatial and temporal characterization of river basins based on Synthetic Aperture Radar (SAR) imagery were discussed. The river basins under study were Sardinia, Italy, based Flumendosa and the larger Meuse basin. The statistical analysis of the processed SAR image provided aid in the development of an aggregation methodology for the generation of large scale soil moisture maps. The utilization of principle component transformation approach during the multitemporal analysis of the obtained satellite images was also discussed.
• Schüttrumpf, H., Troch, P., Van, B., Rouck, J. D., & Oumeraci, H. (2000). Prototype run-up velocities at zeebrugge breakwater. Coastal Engineering 2000 - Proceedings of the 27th International Conference on Coastal Engineering, ICCE 2000, 276, 2018-2029.
  More info

  Abstract: Wave run-up measurements at the rubble mound breakwater of Zeebrugge were analysed to obtain wave run-up and wave run-down velocities at prototype scale. A simple energy equation was applied to predict wave run-up and wave run-down velocities and calibrated by using field data. In addition, existing methods to calculate wave-run-up velocities were reviewed and discussed.
• Troch, P., Rouck, J. D., & Frigaard, P. (2000). Performance of numerical boundary condition based on active wave absorption system. Coastal Engineering 2000 - Proceedings of the 27th International Conference on Coastal Engineering, ICCE 2000, 276, 505-518.
  More info

  Abstract: The implementation and performance of a new active wave generating-absorbing boundary condition for a numerical model based on the Volume Of Fluid (VOF) method for tracking free surfaces is presented. This numerical boundary condition AWAVOF is based on an active wave absorption system that was first developed in the context of physical wave flume experiments, using a wave paddle. The method applies to regular and irregular waves. Velocities are measured at one location inside the computational domain. The reflected wave train is separated from the incident wave field in front of a structure by means of digital filtering and subsequent superposition of the measured velocity signals. The incident wave signal is corrected, so that the reflected wave is effectively absorbed at the boundary. The effectiveness of the active wave generating-absorbing boundary condition is proved using numerical simulations with VOFbreak2.
• Verhoest, N. E., & Troch, P. A. (2000). Erratum: Some analytical solutions of the linearized Boussinesq equation with recharge for a sloping aquifer (Water Resources Research (2000) 36:3 (793-800)). Water Resources Research, 36(7), 1989-.
• Verhoest, N. E., Hoeben, R., P., F., & Troch, P. A. (2000). Soil moisture inversion from ERS and SIR-C imagery at the Zwalm catchment, Belgium. International Geoscience and Remote Sensing Symposium (IGARSS), 5, 2041-2043.
  More info

  Abstract: Several models have been presented in the recent past which should allow soil moisture inversion from bare soil radar backscattering. Three widely used models (i.e. the IEM, the models of Dubois et al. and of Oh et al.) have been applied to ERS and SIR-C data obtained over the Zwalm catchment in Belgium. Results show an inability of the models to estimate surface soil moisture accurately through direct inversion. However, applying the method of effective roughness parameters on the multi-temporal ERS tandem mission data resulted in a significant improvement of the soil moisture retrieval. The same method applied to multi-frequency SIR-C data was not able to improve the estimations. It is believed that the inversions suffer from the high soil roughness sensitivity of the backscattering at higher incidence angles.
• Verhoest, N., & Troch, P. A. (2000). Some analytical solutions of the linearized Boussinesq equation with recharge for a sloping aquifer. Water Resources Research, 36(3), 793-800.
• Herpe, Y. V., Troch, P. A., Callewier, L., & Troch, F. D. (1999). A conceptual model for simulation of catchment scale nitrate transport. IAHS-AISH Publication, 181-191.
  More info

  Abstract: A conceptual catchment-scale model for simulating nitrate transport in rural watersheds is presented. The model consists of a hydrological part and a nitrate transport module. The latter comprises two functions: a production function controlling nitrate release from the unsaturated zone and a transfer function controlling the discharge of nitrate in the surface water. The production function simulates surface runoff and nitrate leaching towards the saturated zone in response to effective rainfall, duration of the leaching period and initial soil nitrate content of the leaching period. The transfer function defines a proportional relation between the catchment soil saturation deficit and the nitrate concentration in the surface water. The model is found to be applicable for two different catchments under humid temperate climatic conditions.
• Mancini, M., Hoeben, R., & Troch, P. A. (1999). Multifrequency radar observations of bare surface soil moisture content: A laboratory experiment. Water Resources Research, 35(6), 1827-1838.
  More info

  Abstract: This paper reports on a laboratory experiment that investigates the use of active microwave observations to estimate volumetric soil moisture content. The experiment, held in 1995, was set up at the European Microwave Signature Laboratory, Joint Research Centre of the European Communities, Ispra (Italy). Full polarimetric radar observations of a 2 m diameter cylindric container filled with a sandy loam soil were performed. During successive wetting and drying cycles, different soil moisture profiles were generated and observed in situ by means of time domain reflectometry probes. The radar data are analyzed based on the Integral Equation Model that simulates radar backscattering given known surface characteristics, such as moisture content and roughness. This allows the evaluation of the predictive power of the simulation model. We find general good agreement between measurements and simulations, but problems occur at high incidence angles. The model is then used to invert soil moisture information from radar measurements. It is shown that, in spite of the complexity of the model involved, it is possible to retrieve under certain circumstances reliable soil moisture estimates with similar accuracies as the in situ measurements.
• Troch, P., & Rouck, J. D. (1999). An active wave generating-absorbing boundary condition for VOF type numerical model. Coastal Engineering, 38(4), 223-247.
  More info

  Abstract: The objective of the present work is to discuss the implementation of an active wave generating-absorbing boundary condition for a numerical model based on the Volume Of Fluid (VOF) method for tracking free surfaces. First an overview of the development of VOF type models with special emphasis in the field of coastal engineering is given. A new type of numerical boundary condition for combined wave generation and absorption in the numerical model VOFbreak2 is presented. The numerical boundary condition is based on an active wave absorption system that was first developed in the context of physical wave flume experiments, using a wave paddle. The method applies to regular and irregular waves. Velocities are measured at one location inside the computational domain. The reflected wave train is separated from the incident wave field in front of a structure by means of digital filtering and subsequent superposition of the measured velocity signals. The incident wave signal is corrected, so that the reflected wave is effectively absorbed at the boundary. The digital filters are derived theoretically and their practical design is discussed. The practical use of this numerical boundary condition is compared to the use of the absorption system in a physical wave flume. The effectiveness of the active wave generating absorbing boundary condition finally is proved using analytical tests and numerical simulations with VOFbreak2.
• Van Herpe, Y., Troch, P. A., Callewier, L., & De, T. F. (1999). A conceptual model for simulation of catchment scale nitrate transport. IAHS-AISH Publication, 181-191.
• Herpe, Y. V., Troch, P. A., Callewier, L., & Quinn, P. F. (1998). Application of a conceptual catchment scale nitrate transport model on two rural river basins. Environmental Pollution, 102(SUPPL. 1), 569-577.
  More info

  Abstract: A conceptual catchment scale model for simulating nitrate transport in rural river basins has been developed. The model consists of a hydrological part based on the TOPMODEL and a nitrate-leaching module. This module consists of two functions: the SLIM-concept controlling the release of nitrate from the soil root zone and second, a transfer function based on the 'flushing hypothesis' controlling the appearance of nitrate in the stream channel network. The SLIM-concept divides the soil into layers with mobile and immobile categories of water and dissolved solids. Movement of water and dissolved solids between the different layers occurs in response to effective rainfall. The transfer function defines a proportional relation between the decline in catchment mean groundwater table and the nitrate concentrations in the stream channel network. Comparison with field data shows reliable simulation results for two different rural catchments, although improvements can be expected when topographical data and field data on the nitrate content in the soil profile at the onset of winter drainage are taken into account.
• Rouck, J. D., Verdonck, R., Troch, P., Damme, L. V., Schlutter, F., & Ronde, J. D. (1998). Wave run-up and overtopping: prototype versus scale models. Proceedings of the Coastal Engineering Conference, 1, 1039-1052.
  More info

  Abstract: The determination of the crest level is one of the most important points in the design of sloping coastal structures. The crest level of sloping coastal structures is governed by wave run-up and overtopping. Recent measurement results of run-up on prototype have indicated that wave run-up may be underpredicted by scale model tests. So full scale measurements of wave run-up is necessary. At the same time the overtopping discharge on a prototype breakwater will be measured. Within the MAST III - OPTICREST project, these measurements will be carried out at coastal structures at two locations: Zeebrugge (Belgium) and Petten (The Netherlands). The results obtained from these prototype measurements will be compared with those from scale model tests and will be used to calibrate numerical models. This paper also presents the contents of the OPTICREST project.
• Schoups, G., Troch, P. A., & Verhoest, N. (1998). Soil moisture influences on the radar backscattering of sugar beet fields. Remote Sensing of Environment, 65(2), 184-194.
  More info

  Abstract: The objective of this article is to investigate the possibility of soil moisture retrieval from radar backscatter data in sugar beet fields. The analysis is based on a simulation study using two models capable of computing electromagnetic backscattering from a vegetated surface, viz., the model developed by Karam et al. (199.5) and the model developed by Lang (1981). First, we validate the models based on data from the AGRISCATT'88 field campaign, held in Flevoland, The Netherlands. The data collected during this campaign allows us to test the model predictions under different soil surface and canopy conditions and for different radar configurations. In general, both models are capable of mimicking the change in backscattering due to changes in radar configuration and surface-vegetation characteristics. Next, both models are subjected to a sensitivity analysis with respect to different surface and canopy parameters. Based on this sensitivity analysis, it is concluded that estimates of surface soil moisture content under a medium sugar beet cover (15 cm high crop)from L-band radar observations are only possible within 10% accuracy. For a fully developed sugar beet field (50 cm high crop), soil moisture retrieval is not possible.
• Troch, P., & Rouck, J. D. (1998). Development of two-dimensional numerical wave flume for wave interaction with rubble mound breakwaters. Proceedings of the Coastal Engineering Conference, 2, 1638-1649.
  More info

  Abstract: The numerical wave flume VOFbreak for simulation of wave interaction with a rubble mound breakwater is presented. The key innovations are a porous flow model and wave boundary conditions. The porous flow is implemented using a Forchheimer model. At the boundaries waves are generated using a combined wave generation-absorption technique and are absorped using a numerical sponge layer.
• Troch, P., Rouck, J. D., & Damme, L. V. (1998). Instrumentation and prototype measurements at the Zeebrugge rubble mound breakwater. Coastal Engineering, 35(1-2), 141-166.
  More info

  Abstract: The prototype monitoring system at Zeebrugge (Belgium), instrumented for the acquisition of field data on waves interacting with a rubble mound breakwater, is presented. To date, the monitoring system has been successfully put into operation and the acquired field data used for the calibration of physical and numerical models. The instrumentation and the data acquisition sections of the monitoring system are described. Experience of more than ten years is made available to those who deal with instrumentation in harsh maritime conditions. Two instrumentation systems are presented in more detail: pore pressure sensors for the measurement of internal pore pressures and stepgauges for the measurement of the wave run-up and run-down. Algorithms used for analysis of acquired field data are included.
• Verhoest, N. E., Troch, P. A., Paniconi, C., & P., F. (1998). Mapping basin scale variable source areas from multitemporal remotely sensed observations of soil moisture behavior. Water Resources Research, 34(12), 3235-3244.
  More info

  Abstract: Soil moisture is an important and highly variable component of the hydrologic cycle. Active microwave remote sensing offers the potential for frequent observation of soil moisture at basin and regional scales. Notwithstanding recent advances, the goal of obtaining accurate and reliable measurements or maps of soil moisture from these instruments remains elusive. The main difficulties for active sensors such as synthetic aperture radar (SAR) are the combined effects of soil moisture, surface roughness, and vegetation on the backscattered signal. We show that it is possible to separate soil moisture information from the other physical factors that dominate the radar backscattering, such as topography and land cover, through a principal component analysis of a time series of eight European Remote Sensing (ERS) SAR images. The soil moisture patterns observed in one of the principal components are consistent with the rainfall-runoff dynamics of a catchment and reflect the variable source areas occuring in the vicinity of the river network.
• Hoeben, R., Troch, P. A., Zhongbo, S. u., Mancini, M., & Chen, K. (1997). Sensitivity of radar backscattering to soil surface parameters: A comparison between theoretical analysis and experimental evidence. International Geoscience and Remote Sensing Symposium (IGARSS), 3, 1368-1370.
  More info

  Abstract: The understanding of the sensitivity of radar backscattering to surface parameters is essential in applying microwave remote sensing to the retrieval of geo- and bio-physical parameters. A theoretical model, the Integral Equation Model, is used to investigate the sensitivity of radar backscattering to soil surface parameters. This model is first tested against a dataset retrieved under well controlled conditions at the European Microwave Signature Laboratory, Joint Research Centre, Ispra, Italy. Then the surface roughness parameters are normalized with respect to wavelength and incidence angle to improve our insight into the sensitivity of radar observations to surface roughness. In this way the roughness space can be subdivided in two regions where surface slope controls the dependency of the signal to roughness.
• Paniconi, A., Verhoest, ., & Troch, P. A. (1997). Soil moisture mapping from multitemporal analys of ERS SAR images. Earth Observation Quarterly, 23-27.
• Schoups, G., Troch, P. A., & Verhoest, N. (1997). Radar bBackscattering sensitivity to soil moisture content of sugar beet fields. Proceedings of SPIE - The International Society for Optical Engineering, 3222, 131-142.
  More info

  Abstract: The objective of this paper is to investigate the possibility of soil moisture retrieval from radar backscatter data in sugar beet fields. The analysis is based on a simulation study using two models capable of computing electromagnetic backscattering from a vegetated surface, viz. the model developed by Karam et al. and the model developed by Lang. First, we validate the models based on data from the AGRISCATT'88 field campaign, held in Flevoland, The Netherlands. The data collected during this campaign allows us to test the model predictions under different soil surface and canopy conditions and for different radar configurations. In general, both models are capable of mimicing the change in backscattering due changes in radar configuration and surface-vegetation characteristics. Next, both models are subjected to a sensitivity analysis with respect to different surface and canopy parameters. Based on this sensitivity analysis it is concluded that estimates of surface soil moisture content under a medium sugar beet cover (15 cm high crop) from L-band radar observations is only possible within 10% accuracy. For a fully developed sugar beet field (50 cm high crop), soil moisture retrieval is not possible.
• Schoups, G., Troch, P. A., & Verhoest, N. (1997). Radar backscattering sensitivity to soil moisture content of sugar beet fields. Earth Surface Remote Sensing. Proc. SPIE conference, London, 1997, 131-142.
• Su, Z., Troch, P. A., & De, T. F. (1997). A method for retrieving soil moisture using active microwave data. Physics and Chemistry of the Earth, 22(3-4), 235-239.
• Su, Z., Troch, P. A., & De, T. F. (1997). Remote sensing of bare surface soil moisture using EMAC/ESAR data. ESA - Workshop Preliminary Proceedings, 136, 53-70.
• Su, Z., Troch, P. A., & De, T. F. (1997). Remote sensing of bare surface soil moisture using EMAC/ESAR data. International Journal of Remote Sensing, 18(10), 2105-2124.
• Su, Z., Troch, P. A., & Troch, F. D. (1997). A method for retrieving soil moisture using active microwave data. Physics and Chemistry of the Earth, 22(3-4), 235-239.
  More info

  Abstract: In this paper we present a method of effective roughness parameters for soil moisture retrieval using SAR (Synthetic Aperture Radar) data. The method is based on simultaneous retrieval of surface roughness parameters and soil moisture by means of inverting a theoretical backscattering model using multiple SAR measurements as inputs. First results of surface soil moisture retrieval are presented, using data from the European Multisensor Airborne Campaign / Experimental Synthetic Aperture Radar (EMAC/ESAR) collected on April 9, 1994 in the Zwalm catchment, Belgium. Promising results for retrieved soil moisture confirm the validity of the proposed method. © 1997 Published by Elsevier Science Ltd.
• Su, Z., Troch, P. A., & Troch, F. D. (1997). Remote sensing of bare surface soil moisture using EMAC/ESAR data. ESA - Workshop Preliminary Proceedings, 136, 53-70.
  More info

  Abstract: In this paper we present first results of bare surface soil moisture retrieval using data from the European Multisensor Airborne Campaign/Experimental Synthetic Aperture Radar (EMAC/ESAR) collected on April 19, 1994 in the Zwalm catchment, Belgium. Data from EMAC Reflective Optics System Imaging Spectrometer (ROSIS) collected on July 12, 1994 over the same catchment were used to develop land use maps. Concurrent to the EMAC/ESAR overflights field data were collected in two subcatchments of the Zwalm catchment. The paper first presents the data processing procedures used for the radar images. Then we apply a theoretical backscattering model to investigate the sensitivity of EMAC/ESAR backscattering coefficients to surface parameters (topography, surface roughness, vegetation and soil moisture). By comparing the predicted backscattering coefficients to the observed ones, we can conclude that classical measurement techniques for surface roughness parameters in remote sensing campaigns are not accurate enough for retrieving soil moisture using theoretical models. A method based on simultaneous retrieval of surface roughness parameters and soil moisture using multiple ESAR measurements is hence proposed. Promising results for retrieved soil moisture confirm the validity of the proposed method.
• Su, Z., Troch, P. A., & Troch, F. D. (1997). Remote sensing of bare surface soil moisture using EMAC/ESAR data. International Journal of Remote Sensing, 18(10), 2105-2124.
  More info

  Abstract: In this paper we present first results of bare surface soil moisture retrieval using data from the European Multisensor Airborne Campaign/ Experimental Synthetic Aperture Radar (EMAC ESAR) collected on 9 April 1994 in the Zwalm catchment, Belgium. Data from EMAC Reflective Optics System Imaging Spectrometer (ROSIS) collected on 12 July 1994 over the same catchment were used to develop land use maps. Concurrent to the EMAC/ESAR overflights field data were collected in two subcatchments of the Zwalm catchment. The paper first presents the data processing procedures used for the radar images. Then we apply a theoretical backscattering model to investigate the sensitivity of EMAC/ESAR backscattering coefficients to surface parameters (topography, surface roughness, vegetation and soil moisture). By comparing the predicted backscattering coefficients to the observed ones, we can conclude that classical measurement techniques for surface roughness parameters in remote sensing campaigns are not accurate enough for retrieving soil moisture using theoretical models. A method based on simultaneous retrieval of surface roughness parameters and soil moisture using multiple ESAR measurements is hence proposed. Promising results for retrieved soil moisture confirm the validity of the proposed method.
• Troch, P. (1997). VOFbreak², a numerical model for simulation of wave interaction with rubble mound breakwater. Proceedings, Congress of the International Association of Hydraulic Research, IAHR, B pt 2, 1366-1371.
  More info

  Abstract: A new free-surface flow model, VOFbreak2, is presented. This numerical model obtains finite difference solutions for incompressible flow on and in coastal structures, such as rubble mound breakwaters. The key innovation is the implementation of a porous flow model, which represents the flow in the coarse granular rock material of breakwaters. Other features include the VOF free-surface treatment, incident wave boundaries, portability of the code and adequate post-processing tools. The unique possibility to validate the model with prototype data from field monitoring is discussed.
• Troch, P. A., Troch, F. D., Grayson, R., Western, A., Derauw, D., & Barbier, C. (1997). Spatial organization of hydrological processes in small catchments derived from advanced SAR image processing: Field work and preliminary results. European Space Agency, (Special Publication) ESA SP, 93-97.
  More info

  Abstract: The presented research focusses on the use of active microwave observations to retrieve hydrologically relevant information of surface characteristics (i.e. soil moisture and surface roughness) in river catchments. Given the availability of pairs of SAR data from the tandem mission the following research issues are addressed: (1) development and testing of improved retrieval algorithms for surface characteristics based on the combined use of phase and magnitude information of the return signal from active microwave sensors; (2) use of high resolution field collected data and remotely sensed data to test and validate theories for the catchment scale estimation of soil moisture integrated over soil depth. In particular questions to be investigated include: (2a) what spatial resolution is required for estimation of spatial average soil moisture patterns over a range of scales; (2b) what temporal resolution is required for accurate estimation of the time series of soil moisture.; (2c) what spatial and temporal resolution of data is required to obtain information about the dynamics of soil moisture redistribution within the soil profile using distributed hydrological modelling; (3) study of the influence that spatial organization of soil moisture and vegetation on SAR-based soil moisture retrieval, and of the ability to identify such organization using ERS data. In order to accomplish these objectives extensive field campaigns are organized in two small experimental catchments (Tarrawarra near Melbourne, Australia and Wijlegemse beek near Gent, Belgium). For both catchments a number of ERS-1/2 tandem scenes have been collected. Both Single Look Complex (SLC) and Precision Image (PRI) data will be required to carry out the different steps in the proposed project.
• Troch, P. A., Zhongbo, S. u., Colombo, P., & Masi, F. D. (1997). Active microwave soil moisture sensing under vegetation cover. Proceedings of SPIE - The International Society for Optical Engineering, 2959, 84-93.
  More info

  Abstract: Our understanding of the derivation of soil moisture content from observing the interaction between electromagnetic waves and bare soil on the one hand, and vegetated terrain on the other has developed at different rates. The retrieval of soil moisture from radar measurements for bare surfaces is possible by means of inversion algorithms based on theoretical surface scattering models (e.g. Su et al. , 1996). The interaction between electromagnetic waves and vegetated terrain involves both surface and volume scattering. The development of theoretical models for vegetated terrain is therefore extremely difficult. One such attempt was initiated by Lang (1981) and resulted in the development of a backscattering model following the wave approach (Lin et al., 1994). We use this model to investigate the effect of different crop parameters on the radar signal. This results in the definition of the conditions under which retrieval of soil moisture is still possible. These conditions are expressed both in terms of vegetation parameters (height, density, water content) and antenna configuration (frequency, polarization, incidence angle). ©2004 Copyright SPIE - The International Society for Optical Engineering.
• Troch, P., Somer, M. D., Rouck, J. D., Damme, L. V., Vermeir, D., Martens, J., & Hove, C. V. (1997). Full scale measurements of wave attenuation inside a rubble mound breakwater. Proceedings of the Coastal Engineering Conference, 2, 1916-1929.
  More info

  Abstract: At the Zeebrugge harbour (Belgium) a cross-section of the N.W.-breakwater has been instrumented for the study of physical processes related to the behaviour of a prototype rubble mound breakwater in random wave conditions. Within the EC MAST programme (project MAS02-CT92-0023) this monitoring system has been re-engineered and extended to a high-quality full scale data acquisition centre (Troch et al., 1995). The development of the prototype monitoring system to a world-wide unique system with respect to the infrastructure available at Zeebrugge, the instrumentation installed on site, and the data management developed, is briefly summarized. Filed measurements of wave attack in front of the breakwater, and pore pressure response inside the breakwater core, have been analyzed in order to determine the hydraulic response of the full scale breakwater. Analysis results on wave run-up/run-down measurements, phreatic set-up calculations, and pore pressure wave attenuation are presented here in more detail.
• Verhoest, N., Troch, P. A., & De, T. F. (1997). On the applicability of Bartlett-Lewis rectangular pulses models in the modeling of design storms at a point. Journal of Hydrology, 202(1-4), 108-120.
• Verhoest, N., Troch, P. A., & P., F. (1997). On the applicability of Bartlett-Lewis rectangular pulses models in the modeling of design storms at a point. Journal of Hydrology, 202(1-4), 108-120.
  More info

  Abstract: This paper discusses the applicability of three versions of the Bartlett-Lewis rectangular pulses model of temporal rainfall for the calculation of design storms. We consider the original model, the modified model (developed in order to improve the zero depth probability) and the modified gamma model. This last model was recently suggested by Onof and Wheater [Onof, C. and Wheater, H.S., J. Hydrol., 157 (1994) 177-195] to improve the representation of extreme rainfall events. The data set used here is 27 years of 10 min rainfall records observed at Uccle (Belgium) between 1967 and 1993. First, the performance of the three models to preserve first- and second-order moments is evaluated. Overall, the modified Bartlett-Lewis model fits best the observed time series. Then, the models are applied to extrapolation of data sets for extreme value frequency analysis of rainfall in order to improve estimates of design intensities for return periods up to 100 years. For the data used here the modified Bartlett-Lewis gamma model does not produce the expected result: an improved representation of extreme rainfall events is not observed. Finally, interstorm variability, important in design storm selection, is analyzed based on time distribution behavior during heavy storms. It is found that all three models represent reasonably well the internal storm structure, but that the average storm duration is underestimated.
• Verhoest, N., Troch, P. A., Deckmyn, J., Paniconi, C., & Troch, F. D. (1997). Spatial soil moisture mapping through multi-temporal analysis of ERS-SAR pri data. European Space Agency, (Special Publication) ESA SP, 99-106.
  More info

  Abstract: The scattering of microwaves from soil depends on several surface characteristics, such as the roughness, vegetation and the moisture content of the top layer. Knowledge of the temporal and spatial distribution of this last parameter is of major importance to hydrologic, meteorologic and climatologic modelling. However accurate measurements of the spatial distribution of soil moisture with classical methods have always been a difficult task. Owing to its dependency on soil moisture and its spatial character, radar remote sensing holds much promise. Several empirical and physically based scattering models have been proposed to retrieve soil moisture values from SAR data, but problems occur with the identification of the roughness and vegetation parameters. This can be partly overcome through the use of multi-frequency and/or multi-polarization radar, but this option is often not available on spaceborne platforms. However, single frequency and single polarization data allows one to map saturation-prone areas using a multi-temporal analysis. The use of multi-temporal data makes it possible to retrieve spatial soil moisture patterns within the studied catchment by applying statistical methods to the time series of images. Two methods for the analysis of a winter time series of ERS-1 and ERS-2 images, for which constant roughness and vegetation conditions can be assumed, are suggested. The first method is based on the temporal coefficient of variation. Since the variability of soil moisture is expected to be smaller near a stream then further upslope from the stream, a smaller temporal coefficient of variation of the returned signal is observed near streams. The second method makes use of principal component analysis of the winter time series of images. Both methods lead to a representation of the spatial distribution of the soil moisture at the catchment scale. However, principal component transformation performs better since it can separate the soil moisture component in the backscattered signal from other influencing factors such as topography and land use.
• Walker, J. P., Troch, P. A., Mancini, M., Willgoose, G. R., & Kalma, J. D. (1997). Profile soil moisture estimation using the modified IEM. International Geoscience and Remote Sensing Symposium (IGARSS), 3, 1263-1265.
  More info

  Abstract: A variable transition rate factor is proposed for the modified IEM, such that it uses a variable dielectric profile down to the radar observation depth. A theoretical observation depth model is also proposed. It is shown that radar observation depth calculated by this model agrees with values noted in literature, and that backscattering simulations using the variable transition rate factor compare well with data collected in the European Microwave Signature Laboratory (EMSL) experiments.
• Altese, E., Bolognani, O., Mancini, M., & Troch, P. A. (1996). Retrieving soil moisture over bare soil from ERS 1 synthetic aperture radar data: Sensitivity analysis based on a theoretical surface scattering model and field data. Water Resources Research, 32(3), 653-661.
  More info

  Abstract: In order to assess the retrieval of soil moisture from ERS 1 (European Remote Sensing Satellite) synthetic aperture radar (SAR) data, an inversion procedure based on the integral equation model (IEM) [Fung et al., 1992] is developed. First, the IEM is used to analyze the sensitivity of radar echoes (in terms of the backscattering coefficient σ0) to the surface parameters (roughness and dielectric constant) under ERS 1 SAR configuration. Results obtained for random rough bare soil fields show that the effect of surface roughness is very strong, particularly in the case of smooth surfaces, and that the sensitivity of σ0 to dielectric constant is independent of the radar configuration and the roughness conditions. This means that the range of variation of backscattering with respect to the dielectric constant variation of dry to wet soil remains the same (about 5 dB) for any roughness condition and radar configuration. The possibility of applying the inversion procedure to retrieve soil moisture is investigated using a set of data collected in a test site situated near Naples, Italy, during the Sele Synthetic Aperture Radar experiment (SESAR) campaign (November 1993). Simultaneous with ERS 1 overpasses, dielectric constant and roughness measurements were taken over two flat bare fields. From this analysis it is found that the inversion of backscattering from ERS 1 SAR into soil moisture is not reliable without accurate information on roughness if the surface is smooth. In this case it is observed that the sensitivity to the roughness parameters is much higher than the sensitivity to dielectric constant, so that even a small error in the measurement of this parameter can affect the retrieved value of soil moisture significantly. The inversion procedure provides more reliable soil moisture estimates when surfaces rougher than those analyzed in the field experiment are considered.
• Debruyckere, L. F., Franks, S. W., Beven, K. J., Troch, P. A., & Troch, F. D. (1996). Towards the upscaling of local surface flux models. Physics and Chemistry of the Earth, 21(3 SPEC. ISS.), 183-188.
  More info

  Abstract: Estimation of regional latent and sensible heat fluxes requires the upscaling of local models. One approach is to develop soil-vegetation-atmosphere transfer (SVAT) schemes at different scales (field, catchment and regional scale; e.g. Famiglietti and Wood (1994)). SVAT schemes at larger scales try to aggregate latent and sensible heat fluxes based on knowledge about the spatial distribution (GIS based) or the statistical-dynamic description of atmospheric forcing and internal state variables. Before one can approach this important problem of upscaling, it is necessary to study the impact of the parameters of the field scale SVAT model on the prediction of local fluxes. In this paper, we show results of a Monte Carlo sensitivity analysis performed on a local SVAT model, with data retrieved during the Autumn of 1995 in an experimental catchment in Belgium. During this field campaign, several parameters of the energy and water balance were measured by means of a Bowen ratio system, while soil moisture data were retrieved on a regular basis using an automatic TDR system. The results of the performed sensitivity analysis are presented and evaluated; conclusions are drawn with respect to the upscaling of local SVAT models to the larger scale. © 1997 Elsevier Science Ltd.
• Gyasi-Agyei, Y., P., F., & Troch, P. A. (1996). A dynamic hillslope response model in a geomorphology based rainfall-runoff model. Journal of Hydrology, 178(1-4), 1-18.
  More info

  Abstract: This paper presents a technique for the determination of a dynamic hillslope instantaneous unit hydrograph (IUH) in concert with a variable saturation excess runoff production model using a grid-based digital elevation model (DEM). The total channel network responsible for routing the runoff produced on the catchment is divided into two parts: the main channel network and the hillslope channel network. The hillslope IUH, which routes water from the hillslopes to the main channel network, is essentially the solution of the linear advection-dispersion routing model weighted by the hillslope travel distance distribution of saturated pixels to the main channel network. The shape of the hillslope travel distance is found to consist of an initial spike, representing saturated pixels on the main channel network, and an exponential decay function for those pixels on the hillslope. However, the proportion of saturated pixels on the main channel network varies with total saturated pixels, causing an inverse change of scale of the spike and the exponential decay part. As the number of saturated pixels changes during a storm event, the hillslope IUH is dynamic. The main channel network IUH is also modelled by the linear advection-dispersion model weighted by the normalized width function of the main channel network. Convolution of the hillslope and main channel network IUHs gives the catchment IUH, which is also dynamically changing with the degree of saturation. It is demonstrated that the direct runoff hydrograph is sensitive to the variation of the degree of saturation within and between storm events.
• Su, Z., Troch, P. A., & Troch, F. D. (1996). Remote sensing of soil moisture using EMAC/ESAR data. International Geoscience and Remote Sensing Symposium (IGARSS), 2, 1303-1305.
  More info

  Abstract: In this paper we present first results of surface soil moisture retrieval using data from the European Multisensor Airborne Campaign / Experimental Synthetic Aperture Radar (EMAC/ESAR) collected on April 9, 1994 in the Zwalm catchment, Belgium. We apply a theoretical backscattering model to investigate the sensitivity of EMAC/ESAR backscattering coefficients to surface parameters. By comparing the predicted backscattering coefficients to the observed ones, we can conclude that current measurement techniques for surface roughness parameters in remote sensing campaigns are not accurate enough for retrieving soil moisture using theoretical models. A method based on simultaneous retrieval of surface roughness parameters and soil moisture using multiple ESAR measurements is hence proposed. Promising results on retrieved soil moisture confirm the validity of the proposed method.
• Troch, P. A., Su, Z., & De, T. F. (1996). Remote sensing of surface soil moisture using EMAC/ESAR data. Earth Observation Quarterly, 17-21.
• Troch, P. A., Su, Z., & Troch, F. D. (1996). Remote sensing of surface soil moisture using EMAC/ESAR data. Earth Observation Quarterly, 17-21.
  More info

  Abstract: During the European Multisensor Airborne Campaign 1994 (EMAC 94), the Experimental Synthetic Aperture Radar (ESAR) and the Reflective Optics System Imaging Spectrometer (ROSIS) were flown over an experimental catchment in Belgium. Concurrent to the ESAR overflights, field data were collected in two subcatchments of the Zwalmbeek. The main objective of this remote-sensing experiment was to retrieve spatial information of surface soil moisture content. An inversion algorithm, based on the Integral Equation Model (Fung et al., 1992), was developed to compute field-averaged soil moisture values from two independent radar images. Good agreement between remotely sensed soil moisture and field observations is obtained. Information on soil moisture patterns is then used to calibrate a distributed catchment-scale water balance model. The model allows to compute, based on observed meteorological variables, soil moisture patterns prior and after SAR observations.
• Giacomelli, A., Bacchiega, U., Troch, P. A., & Mancini, M. (1995). Evaluation of surface soil moisture distribution by means of SAR remote sensing techniques and conceptual hydrological modelling. Journal of Hydrology, 166(3-4), 445-459.
  More info

  Abstract: This paper discusses the attempts to derive surface soil moisture information for two catchments under different climates in Europe based on active microwave remote sensing techniques and conceptual hydrological modelling. The two catchments were selected as test sites during the MAC-EUROPE'91 campaign. The first catchment, Slapton Wood, is situated in south-west England. The second catchment, Virginiolo, is situated in Tuscany, Italy. For both sites, multitemporal full polarimetric AIRSAR (C-, L- and P-band) data are available for the summer of 1991. Based on ground-truth data collected during the flights, simple SAR-soil moisture relationships are established. This allows the estimation of the spatial variation of surface soil moisture at the field scale. From hydrological and meteorological data acquired during the experiment, a conceptual water and energy balance model was calibrated. Simulation results for soil moisture are then compared with SAR-based soil moisture estimates. The comparison between sampled, modelled and SAR-derived soil moisture at the transect scale is acceptable, but the spatial patterns of soil moisture predicted by the conceptual model and the SAR images are different owing to the influence of vegetation. The results are also useful in pointing out some of the major problems encountered in the application of SAR data at the catchment scale. © 1995.
• Mancini, M., Vandersteene, F., Troch, P. A., Bolognani, O., Terzaghi, G., D'Urso, G., & Wuthrich, M. (1995). Experimental setup at the EMSL for the retrieval of soil moisture profiles using multifrequency polarimetric data. International Geoscience and Remote Sensing Symposium (IGARSS), 3, 2023-2025.
  More info

  Abstract: Recently, an integrated research programme on the scattering properties of non vegetated terrains has been established at the European Microwave Signature Laboratory (EMSL) of the Joint Research Centre of European Communities [1]. Part of this programme consists of the experimental research on retrieval of soil moisture profiles. The experiment was setup with the objective to create, under controlled conditions, different datasets which enable the study of soil moisture retrieval from microwave observations and the capability to reconstruct soil moisture profiles. Data sets consist of moisture and temperature profiles in a sandy soil using Time Domain Reflectometry (TDR) and Thermo-Couples (TC), in combination with monostatic, multifrequency (1-10 GHz), polarimetric radar measurements. This article describes the experimental setup at EMSL and outlines the methodology used for data analysis. Results of TDR measurements are presented and compared with numerical simulation results.
• Nesti, G., Pampaloni, P., Coppo, P., Hallikainen, M., Mancini, M., Troch, P., & Shonermark, M. v. (1995). Experimental research at the EMSL on scattering properties of non vegetated terrains. International Geoscience and Remote Sensing Symposium (IGARSS), 3, 2020-2022.
  More info

  Abstract: An experimental research programme on the scattering properties of non vegetated terrains has been established at the European Microwave Signature Laboratory (EMSL), integrating different proposals from external users. The programme concerns the investigation of different aspects, including validation of surface scattering models, retrieval of soil moisture profiles, radar response of frozen/thawed soil and wave penetration in low lossy media. Mono and bi-static polarimetric scattering measurements on samples of artificial dielectric material and real soil are performed in the frequency band 1.5-18 GHz. The planned experiments are described and the outcomes of preliminary measurements are discussed.
• Su, Z., Troch, P. A., Troch, F. P., & Schultz, G. A. (1995). Remote sensing in change detection and study of scale problems in a European mesoscale river basin. Proceedings of SPIE - The International Society for Optical Engineering, 2585, 200-211.
  More info

  Abstract: The objectives of the presented work are on developing methods for extracting hydrologically relevant information from remote sensing data. Recognizing the difficulties in applying former land use and land cover classification systems for hydrological studies of river basins, a land use and land cover classification system for the Sauer River Basin, the Ruhr University Bochum-Land Use and Land Cover Classification System (RUB-LUCS), has been developed for providing distributed information for hydrological modeling, for detection of distributed land use changes and for study of scale problems in land use and land use change detection. Applying this system to Landsat data land use time series have been created for hydrological modeling of effects of man-made changes in the Sauer River Basin. To answer the question, what spatial resolution should be used in characterizing land use and land use changes in hydrological modeling of a mesoscale river basin, a study on scale problems has been conducted. As a result, a hydrological significant resolution is found as 1 km by km.
• Su, Z., Troch, P. A., Troch, F. P., Nachtergale, L., & Cosyn, B. (1995). Soil moisture mapping using ERS-1/SAR in the Zwalm catchment. Proceedings of SPIE - The International Society for Optical Engineering, 2585, 112-122.
  More info

  Abstract: In this paper we present some results of surface soil moisture retrieval using data from ERS- 1/SAR collected in 1994. Concurrent to ERS-1/SAR overflights field data were collected over two subcatchments of the Zwalm catchment in Belgium. After presenting a data processing procedure we apply a theoretical backscattering model to the data set. By comparing the calculated backscattering coefficients to the observed ones, we conclude that the measurements of surface roughness parameters in current remote sensing campaigns are not accurate enough for retrieving soil moisture using theoretical backscattering models. A method based on simultaneous retrieval of surface roughness parameters and soil moisture using multiple ERS- 1/SAR measurements is hence proposed. Promising results on retrieved soil moisture confirm the validity of the proposed method.
• Troch, P. A., De, T. F., Mancini, M., & Wood, E. F. (1995). Stream network morphology and storm response in humid catchments. Hydrological Processes, 9(5-6), 575-587.
• Troch, P. A., Troch, F. D., Mancini, M., & Wood, E. F. (1995). Stream network morphology and storm response in humid catchments. Hydrological Processes, 9(5-6), 575-587.
  More info

  Abstract: Applies the physically based mathematical model of stream network morphology, developed by De Vries (1977), to the Zwalmbeek catchment, Belgium. Based on this model and for different climatic conditions (expressed in terms of rainfall characteristics) the first-order stream spacing model and for different climatic conditions (expressed in terms of rainfall characteristics) the first-order stream spacing versus average water-table depth relationship is calculated. From field observations, digital elevation model derived channel network drainage densities and flood event analysis it is concluded that the 1% exceedance probability rainfall can be suggested as representative for the shaping of climatic conditions in the catchment under study. -from Authors
• Benalaya, A., Sebei, H., De Troch, F., Troch, P., & Ennabli, N. (1994). Estimation des p??riodicit??s et de la tendance des temp??ratures moyennes mensuelles en tunisie. Hydrological Sciences Journal, 39(6), 593-603.
• Benalaya, A., Sebel, H., Troch, F. D., Troch, P., & Ennabli, N. (1994). Estimation of periodicities and trend in monthly mean temperatures in Tunisia. Hydrological Sciences Journal/Journal des Sciences Hydrologiques, 39(6), 593-603.
  More info

  Abstract: Data of monthly mean temperatures collected between 1901 and 1988 at six meteorological stations in Tunisia have been studied to estimate their dominant periodicities and their trends. One significant periodicity of 12 months was found in the original series by using the method developed by Siddiqui & Wang (1984) -from English summary
• Lin, D. -., Wood, E. F., Troch, P. A., Mancini, M., & Jackson, T. J. (1994). Comparisons of remotely sensed and model-simulated soil moisture over a heterogeneous watershed. Remote Sensing of Environment, 48(2), 159-171.
  More info

  Abstract: Soil moisture estimates from a distributed hydrologic model and two microwave airborne sensors (Push Broom Microwave Radiometer and Synthetic Aperture Radar) are compared with ground measurements on two different scales, using data collected during a field experiment over a 7.4-k m2 heterogeneous watershed located in central Pennsylvania. It is found that both microwave sensors and the hydrologic model successfully reflect the temporal variation of soil moisture. Watershed-averaged soil moistures estimated by the microwave sensors are in good agreement with ground measurements. The hydrologic model initialized by streamflow records yields estimates that are wetter than observations. The preliminary test of utilizing remotely sensed information as a feedback to correct the initial state of the hydrologic model shows promising results. © 1994.
• Troch, P. A., De, T. F., & Brutsaert, W. (1994). Correction to ???Effective water table depth to describe initial conditions prior to storm rainfall in humid regions??? by Peter A. Troch, Fran??ois P. De Troch, and Wilfried Brutsaert. Water Resources Research, 30(2), 591-591.
• Troch, P. A., Smith, J. A., Wood, E. F., & P., F. (1994). Hydrologic controls of large floods in a small basin: central Appalachian case study. Journal of Hydrology, 156(1-4), 285-309.
  More info

  Abstract: This paper reports the results of empirical and model-based analysis of extreme flood events observed in a small basin. The study catchment, WE-38 Mahantango Creek (7.2 km2), is situated in the North Appalachian Valley and Ridge province of eastern Pennsylvania. Data from four rain gauges and one water level station are available at 5 min intervals. From the observations, 12 flood events were selected for detailed analysis. The data include tropical storm Agnes (21-24 June 1972), which was responsible for one of the most devastating floods in the region. Model-based analysis of hydrologic response is used to study the dominating runoff processes in the catchment. In this study, we use a distributed version of Topmodel to model runoff generation, and a lumped hillslope and channel routing model to model overland flow and channel flow. The runoff generation model relies on a topographic index to predict saturation excess runoff and on Philip's infiltration equation to predict infiltration excess runoff. The runoff routing model is based on the channel network width function and on the drainage basin hillslope function. The relative roles of initial conditions, soil properties and rainfall rates in determining hydrologic response in the basin are investigated. The flood frequency distribution seems to be insensitive to scaled maximum rainfall intensity. However, the flood frequency distribution is strongly affected by the scaled initial storage capacity. Simulated hydrograph characteristics, such as peak discharge, are very sensitive to the overland flow velocity parameter in the routing model. © 1994.
• Velghe, T., Troch, P. A., De, T. F., & Velde, J. (1994). Evaluation of cluster???based rectangular pulses point process models for rainfall. Water Resources Research, 30(10), 2847-2857.
• Velghe, T., Troch, P. A., Troch, F. D., & Van, J. (1994). Evaluation of cluster-based rectangular pulses point process models for rainfall. Water Resources Research, 30(10), 2847-2857.
  More info

  Abstract: This technical note presents a comparison of cluster-based point rainfall models using the historical hourly rainfall data observed between 1949 and 1976 at Denver, Colorado. The geometric Neyman-Scott model yields better results compared to the Poisson Neyman-Scott model. Moreover, the Bartlett-Lewis model is shown to be very sensitive to the sets of moment equations used in the parameter estimation. This sensitivity is not observed in the Neyman-Scott scheme and is believed to be a drawback for applying the Bartlett-Lewis model in hydrologic simulation studies. -from Authors
• Troch, P. A., De, T. F., & Brutsaert, W. (1993). Effective water table depth to describe initial conditions prior to storm rainfall in humid regions. Water Resources Research, 29(2), 427-434.
• Troch, P. A., Mancini, M., Paniconi, C., & Wood, E. F. (1993). Evaluation of a distributed catchment scale water balance model. Water Resources Research, 29(6), 1805-1817.
  More info

  Abstract: The conceptual model relies on a topographic index to predict saturation excess runoff and on Philip's infiltration equation to predict infiltration excess runoff. The numerical model solves the three-dimensional Richards equation describing flow in variably saturated porous media, and handles seepage face boundaries, infiltration excess and saturation excess runoff production, and soil driven and atmosphere driven surface fluxes. It is found that water table dynamics as predicted by the conceptual model are close to the observations in a shallow water well and therefore, that a linear relationship between a topographic index and the local water table depth is found to be a reasonable asumption for catchment scale modeling. However, the hydraulic equilibrium assumption is not valid for the upper 100 cm layer of the unsaturated zone and a conceptual model that incorporates a root zone is suggested. Furthermore, theoretical subsurface flow characteristics from the conceptual model are found to be different from field observations, numerical simulation results, and theoretical baseflow recession characteristics based on Boussinesq's groundwater equation. -from Authors
• Troch, P. A., Smith, J. A., Wood, E. F., & De, T. F. (1993). Empirical and model based analysis of extreme flood events in a humid region.
• Troch, P. A., Smith, J. A., Wood, E. F., & Troch, F. D. (1993). Empirical and model based analysis of extreme flood events in a humid region. Array.
  More info

  Abstract: This paper reports the results of empirical and model based analysis of extreme flood events observed in a small basin situated in a humid region. Based on second order analysis of observed rainfall we have identified a cluster point rainfall model for each month separately. Hydrograph analysis provides information about the characteristics of the hydrologic response during flood events. Model based analysis of hydrologic response is used to study the dominating runoff processes in the catchment. In this study, we use a distributed version of Topmodel (Beven & Kirkby, 1979; Sivapalan et al., 1987) to model runoff generation. The runoff generation model relies on a topographic index to predict saturation excess runoff and on Philip's infiltration equation to predict infiltration excess runoff. The relative roles of initial conditions, soil properties, and rainfall rate in determining hydrologic response in the basin are investigated. The flood frequency distribution seems to be quite insensitive to scaled maximum rainfall intensity. However, in the catchment under study, the flood frequency distribution is very much affected by the scaled initial storage capacity. (Authors)
• Troch, P. A., Smith, J. A., Wood, E. F., & Troch, F. D. (1993). Empirical and model based analysis of extreme flood events in a humid region. Extreme hydrological events. Proc. international symposium, Yokohama, 1993, 245-256.
  More info

  Abstract: Based on second order analysis of observed rainfall a cluster point rainfall model is identified for each month. Hydrograph analysis provides information about the characteristics of the hydrologic response during flood events. Model based analysis of hydrologic response is used to study the dominating runoff processes in the catchment. A distributed version of Topmodel is used to model runoff generation. The runoff generation model relies on a topographic index to predict saturation excess runoff and on Philip's infiltration equation to predict infiltration excess runoff. The relative roles of initial conditions, soil properties, and rainfall rate in determining hydrologic response in the basin are investigated. The flood frequency distribution seems to be quite insensitive to scaled maximum rainfall intensity. However the flood frequency distribution is very much affected by the scaled initial storage capacity. -from Authors
• Troch, P. A., Troch, F. D., & Brutsaert, W. (1993). Effective water table depth to describe initial conditions prior to storm rainfall in humid regions. Water Resources Research, 29(2), 427-434.
  More info

  Abstract: The estimation of the initial storage capacity prior to a given flood event is essential to obtain useful results from storm runoff prediction models based on saturation excess overland flow. It is shown how this effective depth to the water table can be related to streamflow measurements at the outlet of the basin. The analysis is based on Boussinesq's standard hydraulic groundwater theory. The main feature of the present formulation is that it allows the estimation of catchment-scale parameters, namely the aquifer hydraulic conductivity and the average depth to the impervious layer. The estimation of these parameters is based on a drought flow analysis which is consistent with the hydraulic groundwater theory used to develop the described technique. This hydraulic theory is found to be applicable for a catchment under humid temperate climate conditions, namely the Zwalm catchment situation in East-Flanders, Belgium. -from Authors
• Wood, E. F., Lin, D. -., Mancini, M., Thongs, D., Troch, P. A., Jackson, T. J., Famiglietti, J. S., & Engman, E. T. (1993). Intercomparisons between passive and active microwave remote sensing, and hydrological modeling for soil moisture. Advances in Space Research, 13(5), 167-176.
  More info

  Abstract: Soil moisture estimates from a distributed hydrological model and two microwave remote sensors (Push Broom Microwave Radiometer and Synthetic Aperture Radar) were compared with the ground measurements collected during the MAC-HYDRO'90 experiment over a 7.4-km2 watershed in central Pennsylvania. Various information, including rainfall, soil properties, land cover, topography and remote sensing imagery, were integrated and analyzed using an image integration technique. It is found that the hydrological model and both microwave sensors successfully pick up the temporal variation of soil moisture. Results also indicate the spatial soil moisture pattern can be remotely sensed within reasonable accuracy using existing algorithms. Watershed averaged soil moisture estimates from the hydrological model are wetter than remotely sensed data. It is difficult to conclude which instrument yield better performance for the studied case. The choice will be based on the intended applications and information that is available. © 1993.
• Haba??eb, H., Troch, P. A., & De, T. F. (1991). A coupled rainfall-runoff and runoff-routing model for adaptive real-time flood forecasting. Water Resources Management, 5(1), 47-61.
• Habaïeb, H., Troch, P. A., & Troch, F. D. (1991). A coupled rainfall-runoff and runoff-routing model for adaptive real-time flood forecasting. Water Resources Management, 5(1), 47-61.
  More info

  Abstract: This paper describes an adaptive hydrologic modelling technique for real-time flood forecasting. The modelling approach is based on a linear stochastic time-varying representation of the rainfall-runoff process and on the Muskingum routing method formulated as an optimal linear filtering problem. The most general stochastic rainfall-runoff model used for linear forecasting is known as the transfer function noise model. An on-line identification procedure based on an extension of the recursive Instrumental Variable estimator is discussed. The routing procedure, based on the Muskingum method, is written in a state-space representation. This allows real-time updating of the state and the system parameters by means of Kalman filtering. The described method is used to forecast extreme flood events for the River Ourthe (drainage basin: approx 3626 km2), one of the main tributaries of the River Meuse, Belgium. The method is compared with stationary modelling procedures and its superiority based on objective forecasting criteria is demonstrated. © 1991 Kluwer Academic Publishers.
• Troch, P. A., Troch, F. D., & Erdeghem, D. V. (1991). Operational flood forecasting on the River Meuse using on-line identification. Array.
  More info

  Abstract: Operational flood forecasting of the River Meuse in Belgium is based on both hydrologic and hydraulic modelling. The hydrologic models take into account the rainfall-runoff relationships for the main subcatchments. This allows the handling of the spatially-variable hydrologic behaviour of the total basin. Classical modelling procedures such as a time-invariant stochastic approach, cannot handle problems related to the changing dynamics of the hydrologic processes. This paper discusses a methodology based on on-line estimation of parameters, to model short variations in the response of the main subcatchments of the Meuse. The variation of the parameters is modelled by means of a random walk method. Some objective criteria for evaluation forecasting performance are introduced. It can be concluded that, in general, adaptive modelling improves the real-time performance within the linear framework. (A)
• Troch, P. A., Troch, F. D., & Erdeghem, D. V. (1991). Operational flood forecasting on the River Meuse using on-line identification. Hydrology for the water management of large river basins. Proc. symposium, Vienna, 1991, 379-389.
  More info

  Abstract: Operational flood forecasting on the River Meuse in Belgium is based on both hydrologic and hydraulic modelling. The hydrologic models take into account the rainfall-runoff relationships for the main subcatchments. This allows to handle the spatially-variable hydrologic behaviour of the total basin. Classical modelling procedures such as a time-invariant stochastic approach, cannot handle problems related to the changing dynamics of the hydrologic processes. This paper discusses a methodology based on on-line estimation of parameters, to model short variations in the response of the main subcatchments of the Meuse. The variation of the parameters is modelled by means of a random walk method. Some objective criteria for evaluation forecasting performance are introduced. It can be concluded that, in general, adaptive modelling improves the real-time performance within the linear framework. -Authors
• Troch, P. A., Troch, F. D., & Erdeghem, D. V. (1991). Operational flood forecasting on the River Meuse using on-line identification. IAHS Publication (International Association of Hydrological Sciences), 379-389.
  More info

  Abstract: Operational flood forecasting on the River Meuse in Belgium is based on both hydrologic and hydraulic modelling. The hydrologic models take into account the rainfall-runoff relationships for the main subcatchments. This allows to handle the spatially-variable hydrologic behaviour of the total basin. Classical modelling procedures such as a time-invariant stochastic approach, cannot handle problems related to the changing dynamics of the hydrologic processes. This paper discusses a methodology based on on-line estimation of parameters, to model short variations in the response of the main subcatchments of the Meuse. The variation of the parameters is modelled by means of a random walk method. Some objective criteria for evaluation forecasting performance are introduced. It can be concluded that, in general, adaptive modelling improves the real-time performance within the linear framework.
• Troch, P. A., Troch, F. D., & Hyfte, J. V. (1991). Modelling the time-dependent nature of the rainfall-runoff relationship using on-line identification. Hydrological applications of weather radar, 519-530.
  More info

  Abstract: This paper focusses on the problem of real-time calibration of the time-variant rainfall-runoff relationship. Two different approaches to adaptive modelling of dynamic systems, i.e. firstly the introduction of a "forgetting' factor and secondly the use of an additive Q matrix into the recursive algorithms for the linear parmameter estimation problem, are compared. It is found that, from an operational standpoint, the use of an additive Q matrix leads to better forecasting performance. The choice of the additional design parameters however is not trivial and in this paper it is based on a simulation study using several storm events for subcatchments of the river Meuse, Belgium. -Authors
• Troch, P. A., Troch, F. D., & Laureys, J. (1991). Calibration of a water resources simulation model by means of spatially disaggregated runoff data. Computer Methods in Water Resources II, 549-561.
  More info

  Abstract: This paper describes a calibration procedure of a water resources simulation model based on the geomorphologic instantaneous unit hydrograph (giuh). The simulation model will be used as a tool in the planning phase of land consolidatation projects. In order to improve water management in rural catchments situated in the land consolidation area, different alternatives concerning structural measures (such as location and capacity of storage basins) need to be investigated. The selection between alternatives is based on, among other things, environmental impact considerations. One of the main problems in hydrological simulation for small (< 50 km2) rural catchments in Flanders (Belgium) is the lack of discharge measurements. Recently, the problem of prediction for ungauged river basins has been studied through physically meaningful stochastic theories such as the giuh. This giuh-technique is used in the case study presented in the paper. The rainfall-runoff relationship is identified using historical discharge data recorded at a downstream gauging station. The only unknown parameter in the giuh is a parameter representative for the velocity of the water particles in the channel network. This velocity is assumed to be constant throughout the network. Based on this assumption it is possible to calibrate the giuh model for subcatchments upstream from the gauging station. Once the dynamic hydrologic behaviour of the catchment is determined, a flood routing model which can take into account different interior boundary conditions is developed. This simulation model is used to quantify the effects of structural measures such as the implementation of storage basins.
• Troch, F. D., Heynderickx, J., Troch, P. A., & Erdeghem, D. V. (1990). On the usefulness of weather radar data in real-time hydrological forecasting in Belgium. Weather radar networking: seminar on COST Project 73, 462-470.
  More info

  Abstract: Describing rainfall-runoff relationships a linear stochastic black-box modelling technique is chosen, yielding what is known as a transfer function noise model. An important parameter in this representation of the real system is the dead time or concentration time of the system. This parameter directly influences the forecasting horizon. Efforts to extend this forecasting horizon are concentrated on the development of procedures to estimate future precipitation. Research can be directed along two main directions: statistical analysis (e.g. rainfall generators) and forecasting techniques based on meteorologic and weather radar information. Assuming that the error made in estimating precipitation intensities is acceptable, hydrological forecasting can benefit from this information. As a first attempt to incorporate radar information, one can try to develop some decision making procedure to choose between rainfall scenarios. A simulation study is used to appreciate the usefulness of incorporating weather radar data in the flood forecasting model of the river Meuse. -from Authors

Proceedings Publications

• Schillaci, E., Favre, F., Troch, P., & Oliva, A. (2021). Numerical simulation of fluid structure interaction in free-surface flows: the WEC case.
• Cueva, A., Volkmann, T. H., Haren, J., Troch, P. A., & Meredith, L. K. (2019). Net exchange of carbonyl sulfide, carbon monoxide, and carbon dioxide in a highly oligotrophic basaltic soil: a mesocosm study.. In Geophysical Research Abstracts, 21.
• Meredith, L., Cueva, A., Volkmann, T., U'Ren, J., Singer, E., Haren, J., & Troch, P. (2019). Carbonyl sulfide (COS) as a tracer for plant carbon and water cycling: how do recent models from COS science perform in a controlled ecosystem?. In Geophysical Research Abstracts, 21.
• Meredith, L., Spivey, P., Troch, P. A., Volkmann, T., Sengupta, A., & Youngerman, C. (2019, April). Assessing changes in landscape-level microbial communities with noninvasive methods for dynamic mapping. In Joint Genome Institute Annual User Meeting.
• Teuling, A. J., Van, A. S., Troch, P. A., & Hoitink, A. (2006). Entropy and river meander planform.
• Wood, E. F., Boll, J., Bogaart, P., & Troch, P. (2005). The need for a virtual hydrologic laboratory for PUB.
• Western, A., Sadek, T., Wang, L., Grayson, R., Turral, H., & Troch, P. (2001). Is SAR capable of mapping small-scale spatial patterns of soil moisture?.
• Hoeben, R., & Troch, P. A. (2000). Assimilation of active microwave measurements for soil moisture profile retrieval under laboratory conditions.
• Paniconi, C., Troch, P. A., Mancini, M., & Dessena, M. A. (2000). Soil moisture mapping from ASAR imagery for the Flumendosa and Meuse River basins.
• Verhoest, N. E., Hoeben, R., De, T., & Troch, P. A. (2000). Soil moisture inversion from ERS and SIR-C imagery at the Zwalm catchment, Belgium.
• Hoeben, R., Troch, P. A., Su, Z., Mancini, M., & Chen, K. (1997). Sensitivity of radar backscattering to soil surface parameters: A comparison between theoretical analysis and experimental evidence.
• Schoups, G., Troch, P. A., & Verhoest, N. (1997). Radar bBackscattering sensitivity to soil moisture content of sugar beet fields.
• Troch, P. (1997). VOFbreak2, a numerical model for simulation of wave interaction with rubble mound breakwater.
• Troch, P. A., De, T. F., Grayson, R., Western, A., Derauw, D., & Barbier, C. (1997). Spatial organization of hydrological processes in small catchments derived from advanced SAR image processing: Field work and preliminary results.
• Troch, P. A., Su, Z., Colombo, P., & De Masi, F. (1997). Active microwave soil moisture sensing under vegetation cover.
• Verhoest, N., Troch, P. A., Deckmyn, J., Paniconi, C., & De, T. F. (1997). Spatial soil moisture mapping through multi-temporal analysis of ERS-SAR pri data.
• Walker, J. P., Troch, P. A., Mancini, M., Willgoose, G. R., & Kalma, J. D. (1997). Profile soil moisture estimation using the modified IEM.
• Wu, T. D., Chen, K. S., Fung, A. K., Su, Z., Trouch, P., Hoeben, R., & Mancini, M. (1997). Reappraisal of the validity of IEM model.
• Su, Z., Troch, P. A., & De, T. F. (1996). Remote sensing of soil moisture using EMAC/ESAR data.
• D'Urso, G., Giacomelli, A., Mancim, M., & Troch, P. (1995). Remote sensing of surface soil moisture from a spaceborne SAR sensor over the Sele plain.
• Mancini, M., Vandersteene, F., Troch, P. A., Bolognani, O., Terzaghi, G., D'Urso, G., & Wuthrich, M. (1995). Experimental setup at the EMSL for the retrieval of soil moisture profiles using multifrequency polarimetric data.
• Nesti, G., Pampaloni, P., Coppo, P., Hallikainen, M., Mancini, M., Troch, P., & Shonermark, M. (1995). Experimental research at the EMSL on scattering properties of non vegetated terrains.
• Su, Z., Troch, P. A., Troch, F. P., & Schultz, G. A. (1995). Remote sensing in change detection and study of scale problems in a European mesoscale river basin.
• Su, Z., Troch, P. A., Troch, F. P., Nachtergale, L., & Cosyn, B. (1995). Soil moisture mapping using ERS-1/SAR in the Zwalm catchment.
• Troch, P. A., De, T. F., & Laureys, J. (1991). Calibration of a water resources simulation model by means of spatially disaggregated runoff data.
• Troch, P. A., De, T. F., & Van Erdeghem, D. (1991). Operational flood forecasting on the River Meuse using on-line identification.

Presentations

• Chorover, J. D., Troch, P. A., Root, R. A., Amistadi, M. K., Wang, Y., & Mollaneda, J. (2019, Dec). Transport Induced Mineral Dissolution Through Intensive Hydrological Cycles in Incipient Basalt Hillslopes. AGU Fall Meeting. San Francisco, CA: AGU.
• Enquist, B. J., Troch, P. A., Van Haren, J. L., Saleska, S. R., McDowell, N., Leavitt, S. W., Duran, S., & Michaletz, S. (2019, Aug.). Re-evaluating a stable isotope (δ18O) approach for estimating the temperature of photosynthesis. Ecological Society of America Annual Meeting. Louisville, Kentucky: Ecological Society of America.
• Ruiz, J., Troch, P. A., Chorover, J. D., Sengupta, A., Van Haren, J. L., Tfaily, M. M., Hunt, E., Webb, C., Volk, M., & Dontsova, K. M. (2017, December 2017). Carbon and nitrogen accumulation and fluxes on Landscape Evolution Observatory (LEO) slopes. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Troch, P. A., Chorover, J. D., Toyoda, J., Chu, R. K., Hunt, E., Tfaily, M. M., & Dontsova, K. M. (2019, December 2019). B21H-2303: Spatial differences and temporal change in organic matter composition across artificial hillslope during incipient soil formation.. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Durcik, M., Troch, P. A., Zeng, X., & Arevalo Borquez, J. A. (2019, January). Monitoring and Understanding the Atmosphere in an Enclosed Environment. 99th AMS Annual Meeting. Phoenix, AZ.
• Ferriere, R. H., Troch, P. A., Van Haren, J. L., Barron-Gafford, G. A., Gelabert, A., Daval, D., Barre, P., Hunt, E., Massol, F., Llavata, M., Chollet, S., Le Galliard, J., Villasenor, E., Juarez, S., & Dontsova, K. M. (2019, January). Influence of Climate on Plant-Rock Interactions during Early Soil Development.. Science Society of America (SSSA) International Soils Meeting “Soils Across Latitudes”. San Diego, CA: Science Society of America.
• Troch, P. A., Meredith, L., & Cueva, A. (2018, May). Biosphere 2 – Landscape Evolution Observatory: Un experimento a gran escala. Programa Mexicano del Carbono 9th Simposio Internacional del Carbono en Mexico. Sonora, Mexico.
• Volkmann, T. H., Troch, P. A., Youngerman, C., Sengupta, A., & Meredith, L. (2018, August). Noninvasive methods for dynamically mapping microbial populations across an artificial landscape. ISME General Assembly. Leipzig, Germany.
• Dontsova, K. M., Volk, M., Webb, C., Hunt, E., Tfaily, M. M., Van Haren, J. L., Sengupta, A., Chorover, J. D., Troch, P. A., & Ruiz, J. (2017, December 2017). Carbon and nitrogen accumulation and fluxes on Landscape Evolution Observatory (LEO) slopes. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Troch, P. A., Zeng, X., Wang, Y., Van Haren, J. L., Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pelletier, J. D., Niu, G., Monson, R. K., Meredith, L., Alves Meira Neto, A., Matos, K. A., Maier, R. M., Kim, M., Hunt, E. A., , Harman, C. J., et al. (2017, December). Controlled Experiments of Hillslope Co-evolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological change. AGU International Annual Meeting. New Orleans, LA: American Geophysical Union (AGU).
• Villasenor, E., Dontsova, K. M., Juarez, S., Le Galliard, J., Chollet, S., Llavata, M., Massol, F., Barré, P., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2017, December 2017). The effect of elevated CO2 and temperature on nutrient uptake by plants grown in basaltic soil. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Juarez, S., Dontsova, K. M., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2016, April 2016). Effect of elevated CO2 and temperature on abiotic and biologically-driven basalt weathering and C sequestration. 2016 EGU General Assembly. Vienna, Austria: European Geosciences Union.
• Juarez, S., Dontsova, K. M., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2016, October 2016). Effect of CO2 and temperature on basalt weathering and microbial activity.. International Conference on Ecological Sciences sfecologie2016. Marseille, France.
• Marcais, J., Gupta, H. V., Troch, P. A., & deDreusy, J. (2016, Fall). Coupling machine learning with mechanistic models to study runoff production and river flow at the hillslope scale. 2016 Fall Meeting of the American Geophysical Union.
  More info

  Marçais J, H Gupta, P Troch & JR de Dreuzy (2016), Coupling machine learning with mechanistic models to study runoff production and river flow at the hillslope scale, Session NG013: The Interface between Models and Data, 2016 Fall Meeting of the American Geophysical Union, San Francisco CA, Dec 12-16
• Chorover, J. D., Chorover, J. D., Pelletier, J. D., Pelletier, J. D., Breshears, D. D., Breshears, D. D., Mcintosh, J. C., Mcintosh, J. C., Rasmussen, C., Rasmussen, C., Brooks, P. D., Brooks, P. D., Barron-Gafford, G. A., Barron-Gafford, G. A., Gallery, R. E., Gallery, R. E., Ferre, P. A., Ferre, P. A., Meixner, T., , Meixner, T., et al. (2014, September). The Catalina-Jemez CZO: Transformative Behavior of Energy, Water and Carbon in the Critical Zone II. Interactions between Long and Short Term Processes that Control Delivery of Critical Zone Services.. National Critical Zone Observatory All-Hands Meeting.
• Ruiz, J., Barron-Gafford, G. A., Van Haren, J. L., Dontsova, K. M., Troch, P. A., & Chorover, J. D. (2014, December). Rapid CO2 consumption during incipient weathering of a granular basaltic hillslope in the Landscape Evolution Observatory, Biosphere 2.. American Geophysical Union’s Annual Fall Meeting.
• Troch, P. A., Barron-Gafford, G. A., Dontsova, K. M., Fang, Y., Niu, Y., Pangle, L. A., Tuller, M., & Van Haren, J. L. (2014, December). Monitoring and Modeling Water, Energy and Carbon Fluxes at the Hillslope Scale in the Landscape Evolution Observatory.. AGU International Annual Meeting. San Francisco, CA: American Geophysical Union.
• Zaharescu, D., Dontsova, K. M., Burghelea, C., Maier, R. M., Huxman, T. E., & Chorover, J. D. (2014, December). Cracking the Code of Soil Genesis. The Early Role of Rare Earth Elements. American Geophysical Union (AGU) Fall Meeting. San Francisco, CA.

Poster Presentations

• Troch, P. A., Durcik, M., Neto, A. M., Pitaluga, F., Almagro, A., & Oliveira, P. T. (2020, May). CABra: a novel large-scale dataset for Brazilian catchments. EGU General Assembly 2020. Vienna, Austria.
  More info

  We present the Catchments Attributes for Brazil (CABra) dataset. This is the first large-scale dataset for Brazilian catchments and includes data for 1,252 catchments in seven main classes of catchment attributes (CA: streamflow, groundwater, geology, soil, topography, climate, and land-use and land-cover). We have collected and synthetized data from multi-sources (ground stations data, remote sensed data, and gridded data. CABra contains catchments over the six Brazilian biomes: Amazon, Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal. We delineated all catchments using the coordinates of each streamflow station provided by the Brazilian Water Agency (ANA, in Portuguese). We only considered stations with more than 10 years of data records and less than 20% of missing data. Catchment areas range from 9 to 4,670,000 km² and the mean daily streamflow varies from 0.006 to 170,271 m³ s-1. We also calculated several hydrological signatures – based on distribution, frequency and duration, and dynamics of daily streamflow – and climate indices. Additionally, this dataset includes boundary shapefiles, centroids latitude and longitude, and drainage area for each catchment, aside from more than 50 attributes within each CA class. The CABra intends to fill a huge gap of multisource data collection in Brazil. This dataset plays an important role towards a better understanding of the climate-landscape-hydrology related drivers in a country of continental dimensions and heterogeneous landscape characteristics. Moreover, we described the collection and processing methods and discussed the limitations of each of our multiple data sources. Aside from being a potential tool for large-scale studies in hydrology, our extensive dataset is of main importance for the development of high-quality hydrologic studies in Brazil.
• Meredith, L., Troch, P. A., Maier, R. M., Chorover, J. D., Neilson, J. W., Dontsova, K. M., Volkmann, T., Stegen, J., Barberan, A., & Sengupta, A. (2018, August). Structural and functional response of incipient basaltic microbial community to shifts in soil moisture regime. Goldschmidt. Boston, MA.
• Meredith, L., Troch, P. A., Maier, R. M., Chorover, J. D., Neilson, J. W., Dontsova, K. M., Volkmann, T., Stegen, J., Barberan, A., & Sengupta, A. (2019, January). Structural and Functional Response of Microbial Community in an Oligotrophic Basalt Soil System to Shifts in Rainfall Regimes. Soil Science Society of America (SSSA) International Soils Meeting “Soils Across Latitudes”. San Diego, CA: Soil Science Society of America.
• Meredith, L., Troch, P. A., Volkmann, T. H., & Cueva, A. (2018, March). Variability and Environmental Controls of Negative Soil CO2 Fluxes: Insights from a Large Scale Experimental Hillslope. CALS Poster Forum. Tucson, AZ.
• Meredith, L., Troch, P. A., Volkmann, T. H., Cueva, A., & Pappas, J. (2018, August). Net soil exchange of CO2 and CO in a mesocosm experiment with incipient basaltic tephra. UROC and AZDM poster presentations. Tucson, AZ.
• Troch, P. A., Chorover, J. D., Harman, C., Dontsova, K. M., Meredith, L., Wang, Y., Sengupta, A., Meira Neto, A., Matos, K., Hunt, E., Bugaj, A., Abramson, N., Volkmann, T., & Kim, M. (2018, December). H13N-1958 Experimental observation of a hillslope-scale rank StorAge Selection function: Process controls on its functional form, time variability, and hysteresis.. American Geophysical Union fall meeting. Washington, DC: American Geophysical Union.
• Troch, P. A., Chorover, J. D., Hunt, E., Dontsova, K. M., Wang, Y., & Hitzelberger, M. (2018, August). Coupling Hydrologic Processes and Geochemical Weathering Patterns in a Fully Controlled Basaltic Soil Lysimeter. 2018 Undergraduate Research Opportunities Consortium (UROC) symposium. Tucson, AZ: UA Graduate college.
• Troch, P. A., Chorover, J. D., Hunt, E., Dontsova, K. M., Wang, Y., & Hitzelberger, M. (2018, December). ED13E-0792: Coupling Hydrologic Processes and Geochemical Weathering Patterns in a Fully Controlled Basaltic Soil Lysimeter. American Geophysical Union fall meeting. Washington, DC: American Geophysical Union.
• Cueva, A., Volkmann, T. H., Sengupta, A., Troch, P. A., & Meredith, L. (2017, Dec). Linking genes to ecosystem trace gas fluxes in a large-scale model system. AGU International Annual Meeting. New Orleans, LA.
  More info

  Soil microorganisms mediate biogeochemical cycles through biosphere-atmosphere gas exchange with significant impact on atmospheric trace gas composition. Improving process-based understanding of these microbial populations and linking their genomic potential to the ecosystem-scale is a challenge, particularly in soil systems, which are heterogeneous in biodiversity, chemistry, and structure. In oligotrophic systems, such as the Landscape Evolution Observatory (LEO) at Biosphere 2, atmospheric trace gas scavenging may supply critical metabolic needs to microbial communities, thereby promoting tight linkages between microbial genomics and trace gas utilization. This large-scale model system of three initially homogenous and highly instrumented hillslopes facilitates high temporal resolution characterization of subsurface trace gas fluxes at hundreds of sampling points, making LEO an ideal location to study microbe-mediated trace gas fluxes from the gene to ecosystem scales. Specifically, we focus on the metabolism of ubiquitous atmospheric reduced trace gases hydrogen (H2), carbon monoxide (CO), and methane (CH4), which may have wide-reaching impacts on microbial community establishment, survival, and function. Additionally, microbial activity on LEO may facilitate weathering of the basalt matrix, which can be studied with trace gas measurements of carbonyl sulfide (COS/OCS) and carbon dioxide (O-isotopes in CO2), and presents an additional opportunity for gene to ecosystem study. This work will present initial measurements of this suite of trace gases to characterize soil microbial metabolic activity, as well as links between spatial and temporal variability of microbe-mediated trace gas fluxes in LEO and their relation to genomic-based characterization of microbial community structure (phylogenetic amplicons) and genetic potential (metagenomics). Results from the LEO model system will help build understanding of the importance of atmospheric inputs to microorganisms pioneering fresh mineral matrix. Additionally, the measurement and modeling techniques that will be developed at LEO will be relevant for other investigators linking microbial genomics to ecosystem function in more well-developed soils with greater complexity.
• Kaur, R., Sengputa, A., Meredith, L., & Troch, P. A. (2017, Dec). Spatial and temporal heterogeneity of microbial life in artificial landscapes. AGU International Annual Meeting. New Orleans, LA.
  More info

  The Landscape Evolution Observatory (LEO) project at Biosphere 2 consists of three replicated artificial landscapes which are sealed within a climate-controlled glass house. LEO is composed of basaltic soil material with low organic matter, nutrients, and microbes. The landscapes are built to resemble zero-order basins and enable researchers to observe hydrological, biological, and geochemical evolution of landscapes in a controlled environment. This study is focused on capturing microbial community dynamics in LEO soil, pre- and post-controlled rainfall episodes. Soil samples were collected from six different locations and at five depths in each of the three slopes followed by DNA extraction from 180 samples and sent for amplicon and minimal draft metagenome sequencing. The average concentration of DNA recovered from each sample was higher in the post-rainfall samples than the pre-rainfall samples, a trend consistent in all three slopes. The sequence data will be evaluated to reveal heterogeneity of the soil microbes, providing a more exact narrative of the microbes present in each slope and the spatiotemporal trends of microbial life in the landscapes. Next, functional traits will be predicted from the community data and metagenomes to determine whether consistent changes occur with respect to wetting and drying episodes. Together, these results will highlight the relevance of a unique terrestrial ecosystem research infrastructure in supporting interdisciplinary hydrobiogeochemical research.
• Meredith, L., Sengupta, A., Troch, P. A., & Volkmann, T. H. (2017, Dec). Noninvasive methods for dynamic mapping of microbial populations across the landscape. AGU International Annual Meeting. New Orleans, LA.
  More info

  Soil microorganisms drive key ecosystem processes, and yet characterizing their distribution and activity in soil has been notoriously difficult. This is due, in part, to the heterogeneous nature of their response to changing environmental and nutrient conditions across time and space. These dynamics are challenging to constrain in both natural and experimental systems because of sampling difficulty and constraints. For example, soil microbial sampling at the Landscape Evolution Observatory (LEO) infrastructure in Biosphere 2 is limited in efforts to minimize soil disruption to the long term experiment that aims to characterize the interacting biological, hydrological, and geochemical processes driving soil evolution. In this and other systems, new methods are needed to monitor soil microbial communities and their genetic potential over time. In this study, we take advantage of the well-defined boundary conditions on hydrological flow at LEO to develop a new method to nondestructively characterize in situ microbial populations. In our approach, we sample microbes from the seepage flow at the base of each of three replicate LEO hillslopes and use hydrological models to ‘map back’ in situ microbial populations. Over the course of a 3-month periodic rainfall experiment we collected samples from the LEO outflow for DNA and extraction and microbial community composition analysis. These data will be used to describe changes in microbial community composition over the course of the experiment. In addition, we will use hydrological flow models to identify the changing source region of discharge water over the course of periodic rainfall pulses, thereby mapping back microbial populations onto their geographic origin in the slope. These predictions of in situ microbial populations will be ground-truthed against those derived from destructive soil sampling at the beginning and end of the rainfall experiment. Our results will show the suitability of this method for long-term, non-destructive monitoring of the microbial communities that contribute to soil evolution in this large-scale model system. Furthermore, this method may be useful for other study systems with limitations to destructive sampling including other model infrastructures and natural landscapes.
• Troch, P. A., Dwivedi, R., Liu, T., Alves Meira Neto, A., Roy, T., Valdes, R., Durcik, M., Arciniega, S. S., & Brena-Naranjo, J. A. (2017, December). Catchment-scale groundwater recharge and vegetation water use efficiency. 2017 AGU Fall Meeting, Abstract H51B-1260. New Orleans.
  More info

  Precipitation undergoes a two-step partitioning when it falls on the land surface. At the land surface and in the shallow subsurface, rainfall or snowmelt can either runoff as infiltration/saturation excess or quick subsurface flow. The rest will be stored temporarily in the root zone. From the root zone, water can leave the catchment as evapotranspiration or percolate further and recharge deep storage (e.g. fractured bedrock aquifer). Quantifying the average amount of water that recharges deep storage and sustains low flows is extremely challenging, as we lack reliable methods to quantify this flux at the catchment scale. It was recently shown, however, that for semi-arid catchments in Mexico, an index of vegetation water use efficiency, i.e. the Horton index (HI), could predict deep storage dynamics. Here we test this finding using 247 MOPEX catchments across the conterminous US, including energy-limited catchments. Our results show that the observed HI is indeed a reliable predictor of deep storage dynamics in space and time. We further investigate whether the HI can also predict average recharge rates across the conterminous US. We find that the HI can reliably predict the average recharge rate, estimated from the 50th percentile flow of the flow duration curve. Our results compare favorably with estimates of average recharge rates from the US Geological Survey. Previous research has shown that HI can be reliably estimated based on aridity index, mean slope and mean elevation of a catchment (Voepel et al., 2011). We recalibrated Voepel’s model and used it to predict the HI for our 247 catchments. We then used these predicted values of the HI to estimate average recharge rates for our catchments, and compared them with those estimated from observed HI. We find that the accuracies of our predictions based on observed and predicted HI are similar. This provides an estimation method of catchment-scale average recharge rates based on easily derived catchment characteristics, such as climate and topography, and free of discharge measurements.
• Van Haren, J. L., Sanchez-Canete, E., Juarez, S., Howard, E., Dontsova, K. M., Le Galliard, J., Barron-Gafford, G. A., Volkmann, T., & Troch, P. A. (2017, December). Projected effects of vegetation and organic matter on soil carbon dynamics after rainfall in a model basalt landscape. American Geophysical Union fall meeting. New Orleans, LA: American Geophysical Union.
• Volkmann, T. H., Sengupta, A., Pangle, L. A., Abramson, N., Barron-Gafford, G. A., Breshears, D. D., Bugaj, A., Chorover, J. D., Dontsova, K. M., Durcik, M., Ferre, P. A., Harman, C. J., Hunt, E. A., Kim, M., Maier, R. M., Matos, K. A., Alves Meira Neto, A., Meredith, L., Monson, R. K., , Niu, G., et al. (2017, December). Controlled Experiments of Hillslope Co-evolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological change. AGU International Annual Meeting. New Orleans, LA: American Geophysical Union (AGU).
• Dontsova, K. M., Juarez, S., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2016, June 2016). Basalt Weathering under Controlled Conditions as Influenced by Biota, Temperature, and CO2. The 26th Goldschmidt Conference. Yokohama, Japan: The European Association for Geochemistry and Geochemical Society.
• Hingley, R., Dontsova, K. M., Juarez, S., Hunt, E., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2016, December 2016). Effects of Climate Change and Vegetation Type on Carbon and Nitrogen Accumulation during Incipient Soil Formation. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Umanzor, M., Wang, Y., Dontsova, K. M., Chorover, J. D., & Troch, P. A. (2016, December 2016). A Centimeter‐Scale Investigation of Geochemical Hotspots in a Soil Lysimeter. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Juarez, S., Dontsova, K. M., Le Galliard, J., Chollet, S., Cros, A., Llavata, M., Barre, P., Massol, F., Gelabert, A., Daval, D., Troch, P. A., Barron-Gafford, G. A., Van Haren, J. L., & Ferriere, R. H. (2015, 20-24 Sep 2015). Abiotic and biologically-­‐driven basalt weathering and carbon sequestration under changing climate. 5th International Symposium on Soil Organic Matter. Göttingen (DE).
• Chang, H. I., Troch, P. A., Castro, C. L., & Mukherjee, R. (2014, June). Regional climate and streamflow projections in North America under IPCC CMIP5 scenarios. 3rd Lund Regional-scale Climate Modeling Workshop. Lund, Sweden: Lund University.
• Troch, P. A., Barron-Gafford, G. A., Dontsova, K. M., Fang, Y., Niu, Y., Pangle, L., Tuller, M., & Van Haren, J. L. (2014, December). Monitoring and Modeling Water, Energy and Carbon Fluxes at the Hillslope Scale in the Landscape Evolution Observatory. 2014 American Geophysical Union (AGU) Fall Meeting. San Francisco, CA.
• Troch, P. A., Barron-Gafford, G. A., Dontsova, K. M., Fang, Y., Niu, Y., Pangle, L., Tuller, M., & Van Haren, J. L. (2014, December). Monitoring and Modeling Water, Energy and Carbon Fluxes at the Hillslope Scale in the Landscape Evolution Observatory. American Geophysical Union (AGU) Fall Meeting. San Francisco, CA.
• Wu, R., Niu, Y., Chorover, J. D., Dontsova, K. M., & Troch, P. A. (2014, December). Reactive Transport Modelling of Mineral Evolution in the Biosphere 2 Hillslope Experiment. 2014 American Geophysical Union (AGU) Fall Meeting. San Francisco, CA.
• Wu, R., Niu, Y., Chorover, J. D., Dontsova, K. M., & Troch, P. A. (2014, December). Reactive Transport Modelling of Mineral Evolution in the Biosphere 2 Hillslope Experiment. American Geophysical Union (AGU) Fall Meeting. San Francisco, CA.
• Barron-Gafford, G. A., Minor, R. L., van Haren, J., Dontsova, K. M., & Troch, P. A. (2013, December). Precipitation pulse dynamics of carbon sequestration and efflux in highly weatherable soils. Annual Meeting of the American Geophysical Union. San Francisco, CA: American Geophysical Union.
  More info

  Soils are the primary pool for terrestrial carbon on Earth, and loss of that carbon to the atmosphere or hydrosphere represents a significant efflux that can impact a host of other downstream processes. Soil respiration (Rsoil), the efflux of CO2 to the atmosphere, represents the major pathway by which carbon is lost from the soil system in more weathered soils. However, in newly formed soils, chemical weathering can significantly deplete soil CO2 concentrations. As vegetation colonizes these soils, multiple interacting and contradictory pathways evolve such that soil CO2 concentrations increase in response to plant inputs but are decreased through chemical reactions. Furthermore, abiotic drivers of soil temperature and moisture likely differentially affect these processes. Understanding the bio-geo-chemical drivers and feedbacks associated with soil CO2 production and efflux in the critical zone necessitates an integrated science approach, drawing on input from plant physiologists, bio- and geochemists, and hydrologists. Here, we created a series of 1-meter deep mesocosms filled with granular basalt that supported either a woody mesquite shrub, a bunchgrass, or was left as bare soil. Use of multiple plant functional types allowed us to explore the impacts of plant structure (primarily rooting profiles) on critical zone function in terms of water and carbon exchange surrounding precipitation pulse dynamics. Each mesocosm was outfitted with an array of soil moisture, temperature, water potential, and CO2 concentration sensors at the near-surface, 30, 55, and 80cm depths to quantify patterns of soil moisture and respiratory CO2 efflux in response to rainfall events of varying magnitude and intervening periods of drought. Five replicates of each were maintained under current ambient or projected (+4oC) air temperatures. In addition, we used minirhizotrons to quantify the response of roots to episodic rainfall and confirm differences among plant types and collected soils solution samples to quantify dissolved inorganic carbon (DIC), pH, and other solute concentrations.Importantly, we found Rsoil dynamics to be nearly in direct contrast to our classic understanding of patterns of soil CO2 efflux after rain events. Rsoil rates declined immediately upon wetting and gradually increased to pre-rain rates as the soils dried. Investigation into soil CO2 profile data showed that CO2 concentrations just below the surface declined significantly from near-ambient levels to near ~50ppm, which would directly impact rates of Rsoil. We detected differences among plant functional types in terms of rooting depth, water use, photosynthetic uptake, base rates of Rsoil, the time required to return to pre-rain rates of Rsoil, and the rates of soil weathering. Combining aboveground measurements of carbon uptake with these belowground estimates of carbon pools and efflux will allow us to make much more informed projections of carbon dynamics within highly weatherable soils across a range of global climate change projections and plant functional types.Experiment webpage: http://www.u.arizona.edu/~gregbg/Research__Biosphere_2_Mesocosm.htmlParent project webpage: http://leo.b2science.org/
• Breshears, D. D., Breshears, D. D., Field, J. P., Field, J. P., Law, D. J., Law, D. J., Brooks, P. D., Brooks, P. D., Chorover, J., Chorover, J. D., Pelletier, J. D., Pelletier, J. D., Troch, P. A., Troch, P. A., Lopez Hoffman, L., Lopez Hoffman, L. -., Rasmussen, C., Rasmussen, C. -., Papuga, S. A., , Papuga, S. A., et al. (2013, October 2013). Bridging from soil to ecosystem goods and services provided by the Critical Zone. AGU Chapman Conference: Soil-mediated drivers of coupled biogeochemical and hydrological processes across scales. Tucson.

Others

• Destouni, G., Bahr, J., Bierkens, M. F., Clark, M., Hall, J., Islam, S., Kollet, S., Luce, C. H., Lundquist, J., Mackay, D. S., & others, . (2021). Thank you to our 2020 reviewers.
• Clark, M., Bahr, J., Bierkens, M. F., Hall, J., Kollet, S., Luce, C. H., Lundquist, J., Mackay, D. S., Meerveld, I., Sanchez-Vila, X., & others, . (2020). Thank you to our 2019 reviewers.