Computers Geosciences Uncertainty and Sensitivity in Surface Dynamics Modeling

COMPUTERS & GEOSCIENCES Uncertainty and Sensitivity in Surface Dynamics Modeling

CSDMS annual meeting 2014 Uncertainty and Sensitivity in Surface Dynamics Modeling took place May 20-22, 2014 in Boulder Colorado. One of the outcomes was a special issue of Computers & Geosciences, volume 90 part B, ISSN 0098-3004, published April, 2015. Below is an overview of the papers with their abstracts.
We would like to thank all authors as well as the reviewers for their effort!

Content

Uncertainty and Sensitivity in Surface Dynamics Modeling Albert J. Kettner and James P.M. Syvitski

No abstract is available for this article. Albert J. Kettner and James P.M. Syvitski, 2013. Uncertainty and Sensitivity in Surface Dynamics Modeling, Computers & Geosciences, V.90, Part B, 1-5. DOI: 10.1016/j.cageo.2016.03.003

Uncertainty quantification in modeling earth surface processes: more applicable for some types of models than for others A. Brad Murray, Nicole M. Gasparini, Evan B. Goldstein, and Mick van der Wegen

In Earth-surface science, numerical models are used for a range of purposes, from making quantitatively accurate predictions for practical or scientific purposes (‘simulation’ models) to testing hypotheses about the essential causes of poorly understood phenomena (‘exploratory’ models). We argue in this contribution that whereas established methods for uncertainty quantification (UQ) are appropriate (and crucial) for simulation models, their application to exploratory models are less straightforward, and in some contexts not relevant. Because most models fall between the end members of simulation and exploratory models, examining the model contexts under which UQ is most and least appropriate is needed. Challenges to applying state-of-the-art UQ to Earth-surface science models center on quantifying ‘model-form’ uncertainty—the uncertainty in model predictions related to model imperfections. These challenges include: 1) the difficulty in deterministically comparing model predictions to observations when positive feedbacks and associated autogenic dynamics (a.k.a. ‘free’ morphodynamics) determine system behavior over the timescales of interest (a difficulty which could be mitigated in a UQ approach involving statistical comparisons); 2) the lack of available data sets at sufficiently large space and/or time scales; 3) the inability to disentangle uncertainties arising from model parameter values and model form in some cases; and 4) the inappropriateness of model ‘validation’ in the UQ sense for models toward the exploratory end member of the modeling spectrum. A. Brad Murray, Nicole M. Gasparini, Evan B. Goldstein, and Mick van der Wegen, 2013. Uncertainty quantification in modeling earth surface processes: more applicable for some types of models than for others, Computers & Geosciences, V.90, Part B, 6-16. DOI: 10.1016/j.cageo.2016.02.008

Morphological impact of a storm can be predicted three days ahead F. Baart, M. van Ormondt, J.S.M. van Thiel de Vries, and M. van Koningsveld

People living behind coastal dunes depend on the strength and resilience of dunes for their safety. Forecasts of hydrodynamic conditions and morphological change on a timescale of several days can provide essential information to protect lives and property. In order for forecasts to protect they need be relevant, accurate, provide lead time, and information on confidence. Here we show how confident one can be in morphological predictions of several days ahead. The question is answered by assessing the forecast skill as a function of lead time. The study site in the town of Egmond, the Netherlands, where people depend on the dunes for their safety, is used because it is such a rich data source, with a history of forecasts, tide gauges and bathymetry measurements collected by video cameras. Even though the forecasts are on a local scale, the methods are generally applicable. It is shown that the intertidal beach volume change can be predicted up to three days ahead. F. Baart, M. van Ormondt, J.S.M. van Thiel de Vries, and M. van Koningsveld, 2013. Morphological impact of a storm can be predicted three days ahead, Computers & Geosciences, V.90, Part B, 17-23. DOI: 10.1016/j.cageo.2015.11.011

Shelf sediment transport during hurricanes Katrina and Rita Kehui Xu, Rangley C. Mickey, Qin Chen, Courtney K. Harris, Robert D. Hetland, Kelin Hu, and Jiaze Wang

Hurricanes can greatly modify the sedimentary record, but our coastal scientific community has rather limited capability to predict hurricane-induced sediment deposition. A three-dimensional sediment transport model was developed in the Regional Ocean Modeling System (ROMS) to study seabed erosion and deposition on the Louisiana shelf in response to Hurricanes Katrina and Rita in the year 2005. Sensitivity tests were performed on both erosional and depositional processes for a wide range of erosional rates and settling velocities, and uncertainty analysis was done on critical shear stresses using the polynomial chaos approximation method. A total of 22 model runs were performed in sensitivity and uncertainty tests. Estimated maximum erosional depths were sensitive to the inputs, but horizontal erosional patterns seemed to be controlled mainly by hurricane tracks, wave–current combined shear stresses, seabed grain sizes, and shelf bathymetry. During the passage of two hurricanes, local resuspension and deposition dominated the sediment transport mechanisms. Hurricane Katrina followed a shelf-perpendicular track before making landfall and its energy dissipated rapidly within about 48 h along the eastern Louisiana coast. In contrast, Hurricane Rita followed a more shelf-oblique track and disturbed the seabed extensively during its 84-h passage from the Alabama–Mississippi border to the Louisiana–Texas border. Conditions to either side of Hurricane Rita’s storm track differed substantially, with the region to the east having stronger winds, taller waves and thus deeper erosions. This study indicated that major hurricanes can disturb the shelf at centimeter to meter levels. Each of these two hurricanes suspended seabed sediment mass that far exceeded the annual sediment inputs from the Mississippi and Atchafalaya Rivers, but the net transport from shelves to estuaries is yet to be determined. Future studies should focus on the modeling of sediment exchange between estuaries and shelves and the field measurement of erosional rates and settling velocities. Kehui Xu, Rangley C. Mickey, Qin Chen, Courtney K. Harris, Robert D. Hetland, Kelin Hu, and Jiaze Wang, 2013. Shelf sediment transport during hurricanes Katrina and Rita, Computers & Geosciences, V.90, Part B, 24-39. DOI: 10.1016/j.cageo.2015.10.009

Reprint of: A numerical investigation of fine sediment resuspension in the wave boundary layer—Uncertainties in particle inertia and hindered settling Zhen Cheng, Xiao Yu, Tian-Jian Hsu, and S. Balachandar

The wave bottom boundary layer is a major conduit delivering fine terrestrial sediments to continental margins. Hence, studying fine sediment resuspensions in the wave boundary layer is crucial to the understanding of various components of the earth system, such as carbon cycles. By assuming the settling velocity to be a constant in each simulation, previous turbulence-resolving numerical simulations reveal the existence of three transport modes in the wave boundary layer associated with sediment availabilities. As the sediment availability and hence the sediment-induced stable stratification increases, a sequence of transport modes, namely, (I) well-mixed transport, (II) formulation of lutocline resembling a two-layer system, and (III) completely laminarized transport are observed. In general, the settling velocity is a flow variable due to hindered settling and particle inertia effects. Present numerical simulations including the particle inertia suggest that for a typical wave condition in continental shelves, the effect of particle inertia is negligible. Through additional numerical experiments, we also confirm that the particle inertia tends (up to the Stokes number St = 0.2) to attenuate flow turbulence. On the other hand, for flocs with lower gelling concentrations, the hindered settling can play a key role in sustaining a large amount of suspended sediments and results in the laminarized transport (III). For the simulation with a very significant hindered settling effect due to a low gelling concentration, results also indicate the occurrence of gelling ignition, a state in which the erosion rate is always higher than the deposition rate. A sufficient condition for the occurrence of gelling ignition is hypothesized for a range of wave intensities as a function of sediment/floc properties and erodibility parameters. Zhen Cheng, Xiao Yu, Tian-Jian Hsu, and S. Balachandar, 2013. Reprint of: A numerical investigation of fine sediment resuspension in the wave boundary layer—Uncertainties in particle inertia and hindered settling, Computers & Geosciences, V.90, Part B, 40-56. DOI: 10.1016/j.cageo.2015.11.003

Sensitivity of a third generation wave model to wind and boundary condition sources and model physics: A case study from the South Atlantic Ocean off Brazil coast S. Mostafa Siadatmousavi, Felix Jose, and Graziela Miot da Silva

Three different packages describing the white capping dissipation process, and the corresponding energy input from wind to wave were used to study the surface wave dynamics in South Atlantic Ocean, close to the Brazilian coast. A host of statistical parameters were computed to evaluate the performance of wave model in terms of simulated bulk wave parameters. Wave measurements from a buoy deployed off Santa Catarina Island, Southern Brazil and data along the tracks of Synthetic Aperture Radars were compared with simulated bulk wave parameters; especially significant wave height, for skill assessment of different packages. It has been shown that using a single parameter representing the performance of source and sink terms in the wave model, or relying on data from only one period of simulations for model validation and skill assessment would be misleading. The model sensitivity to input parameters such as time step and grid size were addressed using multiple datasets. The wind data used for the simulation were obtained from two different sources, and provided the opportunity to evaluate the importance of input data quality. The wind speed extracted from remote sensing satellites was compared to wind datasets used for wave modeling. The simulation results showed that the wind quality and its spatial resolution is highly correlated to the quality of model output. Two different sources of wave information along the open boundaries of the model domain were used for skill assessment of a high resolution wave model for the study area. It has been shown, based on the sensitivity analysis, that the effect of using different boundary conditions would decrease as the distance from the open boundary increases; however, the difference were still noticeable at the buoy location which was located 200–300 km away from the model boundaries; but restricted to the narrow band of the low frequency wave spectrum. S. Mostafa Siadatmousavi, Felix Jose, and Graziela Miot da Silva, 2013. Sensitivity of a third generation wave model to wind and boundary condition sources and model physics: A case study from the South Atlantic Ocean off Brazil coast, Computers & Geosciences, V.90, Part B, 57-65. DOI: 10.1016/j.cageo.2015.09.025

Understanding hydrological flow paths in conceptual catchment models using uncertainty and sensitivity analysis Eva M. Mockler, Fiachra E. O’Loughlin, and Michael Bruen

Increasing pressures on water quality due to intensification of agriculture have raised demands for environmental modeling to accurately simulate the movement of diffuse (nonpoint) nutrients in catchments. As hydrological flows drive the movement and attenuation of nutrients, individual hydrological processes in models should be adequately represented for water quality simulations to be meaningful. In particular, the relative contribution of groundwater and surface runoff to rivers is of interest, as increasing nitrate concentrations are linked to higher groundwater discharges. These requirements for hydrological modeling of groundwater contribution to rivers initiated this assessment of internal flow path partitioning in conceptual hydrological models. In this study, a variance based sensitivity analysis method was used to investigate parameter sensitivities and flow partitioning of three conceptual hydrological models simulating 31 Irish catchments. We compared two established conceptual hydrological models (NAM and SMARG) and a new model (SMART), produced especially for water quality modeling. In addition to the criteria that assess streamflow simulations, a ratio of average groundwater contribution to total streamflow was calculated for all simulations over the 16 year study period. As observations time-series of groundwater contributions to streamflow are not available at catchment scale, the groundwater ratios were evaluated against average annual indices of base flow and deep groundwater flow for each catchment. The exploration of sensitivities of internal flow path partitioning was a specific focus to assist in evaluating model performances. Results highlight that model structure has a strong impact on simulated groundwater flow paths. Sensitivity to the internal pathways in the models are not reflected in the performance criteria results. This demonstrates that simulated groundwater contribution should be constrained by independent data to ensure results within realistic bounds if such models are to be used in the broader environmental sustainability decision making context. Eva M. Mockler, Fiachra E. O’Loughlin, and Michael Bruen, 2013. Understanding hydrological flow paths in conceptual catchment models using uncertainty and sensitivity analysis, Computers & Geosciences, V.90, Part B, 66-77. DOI: 10.1016/j.cageo.2015.08.015

Reprint of: Active subspaces for sensitivity analysis and dimension reduction of an integrated hydrologic model Jennifer L. Jefferson, James M. Gilbert, Paul G. Constantine, and Reed M. Maxwell

Integrated hydrologic models coupled to land surface models require several input parameters to characterize the land surface and to estimate energy fluxes. Uncertainty of input parameter values is inherent in any model and the sensitivity of output to these uncertain parameters becomes an important consideration. To better understand these connections in the context of hydrologic models, we use the ParFlow-Common Land Model (PF-CLM) to estimate energy fluxes given variations in 19 vegetation and land surface parameters over a 144-hour period of time. Latent, sensible and ground heat fluxes from bare soil and grass vegetation were estimated using single column and tilted-v domains. Energy flux outputs, along with the corresponding input parameters, from each of the four scenario simulations were evaluated using active subspaces. The active subspace method considers parameter sensitivity by quantifying a weight for each parameter. The method also evaluates the potential for dimension reduction by identifying the input–output relationship through the active variable – a linear combination of input parameters. The aerodynamic roughness length was the most important parameter for bare soil energy fluxes. Multiple parameters were important for energy fluxes from vegetated surfaces and depended on the type of energy flux. Relationships between land surface inputs and output fluxes varied between latent, sensible and ground heat, but were consistent between domain setup (i.e., with or without lateral flow) and vegetation type. A quadratic polynomial was used to describe the input–output relationship for these energy fluxes. The reduced-dimension model of land surface dynamics can be compared to observations or used to solve the inverse problem. Considering this work as a proof-of-concept, the active subspace method can be applied and extended to a range of domain setups, land cover types and time periods to obtain a reduced-form representation of any output of interest, provided that an active subspace exists. Jennifer L. Jefferson, James M. Gilbert, Paul G. Constantine, and Reed M. Maxwell, 2013. Reprint of: Active subspaces for sensitivity analysis and dimension reduction of an integrated hydrologic model, Computers & Geosciences, V.90, Part B, 78-89. DOI: 10.1016/j.cageo.2015.11.002

Hydrological model uncertainty due to spatial evapotranspiration estimation methods Xuan Yu, Anna Lamačová, Christopher Duffy, Pavel Krám, and Jakub Hruška

Evapotranspiration (ET) continues to be a difficult process to estimate in seasonal and long-term water balances in catchment models. Approaches to estimate ET typically use vegetation parameters (e.g., leaf area index [LAI], interception capacity) obtained from field observation, remote sensing data, national or global land cover products, and/or simulated by ecosystem models. In this study we attempt to quantify the uncertainty that spatial evapotranspiration estimation introduces into hydrological simulations when the age of the forest is not precisely known. The Penn State Integrated Hydrologic Model (PIHM) was implemented for the Lysina headwater catchment, located 50°03′N, 12°40′E in the western part of the Czech Republic. The spatial forest patterns were digitized from forest age maps made available by the Czech Forest Administration. Two ET methods were implemented in the catchment model: the Biome-BGC forest growth sub-model (1-way coupled to PIHM) and with the fixed-seasonal LAI method. From these two approaches simulation scenarios were developed. We combined the estimated spatial forest age maps and two ET estimation methods to drive PIHM. A set of spatial hydrologic regime and streamflow regime indices were calculated from the modeling results for each method. Intercomparison of the hydrological responses to the spatial vegetation patterns suggested considerable variation in soil moisture and recharge and a small uncertainty in the groundwater table elevation and streamflow. The hydrologic modeling with ET estimated by Biome-BGC generated less uncertainty due to the plant physiology-based method. The implication of this research is that overall hydrologic variability induced by uncertain management practices was reduced by implementing vegetation models in the catchment models. Xuan Yu, Anna Lamačová, Christopher Duffy, Pavel Krám, and Jakub Hruška, 2013. Hydrological model uncertainty due to spatial evapotranspiration estimation methods, Computers & Geosciences, V.90, Part B, 90-101. DOI: 10.1016/j.cageo.2015.05.006

Multi-scale characterization of topographic anisotropy S.G. Roy, P.O. Koons, B. Osti, P. Upton, and G.E. Tucker

We present the every-direction variogram analysis (EVA) method for quantifying orientation and scale dependence of topographic anisotropy to aid in differentiation of the fluvial and tectonic contributions to surface evolution. Using multi-directional variogram statistics to track the spatial persistence of elevation values across a landscape, we calculate anisotropy as a multiscale, direction-sensitive variance in elevation between two points on a surface. Tectonically derived topographic anisotropy is associated with the three-dimensional kinematic field, which contributes (1) differential surface displacement and (2) crustal weakening along fault structures, both of which amplify processes of surface erosion. Based on our analysis, tectonic displacements dominate the topographic field at the orogenic scale, while a combination of the local displacement and strength fields are well represented at the ridge and valley scale. Drainage network patterns tend to reflect the geometry of underlying active or inactive tectonic structures due to the rapid erosion of faults and differential uplift associated with fault motion. Regions that have uniform environmental conditions and have been largely devoid of tectonic strain, such as passive coastal margins, have predominantly isotropic topography with typically dendritic drainage network patterns. Isolated features, such as stratovolcanoes, are nearly isotropic at their peaks but exhibit a concentric pattern of anisotropy along their flanks. The methods we provide can be used to successfully infer the settings of past or present tectonic regimes, and can be particularly useful in predicting the location and orientation of structural features that would otherwise be impossible to elude interpretation in the field. Though we limit the scope of this paper to elevation, EVA can be used to quantify the anisotropy of any spatially variable property. S.G. Roy, P.O. Koons, B. Osti, P. Upton, and G.E. Tucker, 2013. Multi-scale characterization of topographic anisotropy, Computers & Geosciences, V.90, Part B, 102-116. DOI: 10.1016/j.cageo.2015.09.023

Predicting uncertainty in sediment transport and landscape evolution – the influence of initial surface conditions G.R. Hancock, T.J. Coulthard, and J.B.C. Lowry

Open channel flow containing sediment suspension subjects itself to a density gradient in the vertical direction, i.e. density self-stratification, due to the tendency for suspended sediment to settle. Velocity and concentration profiles under the effect of density stratification may differ significantly from the conventional logarithmic and Rousean distributions associated with open channel flow. It is hence important to include this effect into flow computations in order to accurately predict flow characteristics such as the resistance coefficient, near-bed sediment concentration, flow and sediment discharge. In this study we introduce a software, StratSedOC, for such purpose. The application contains a user-friendly interface which allows users to evaluate and visualize the differences in the velocity, concentration and eddy viscosity profiles when stratification effects are taken into account. In addition to the standard logarithmic/Rousean formulation, the model uses three turbulence closures, i.e. an algebraic model (Smith–McLean) and two differential models (k-ε and Mellor–Yamada). The software application can also be used to study the effect of sediment mixtures on flow stratification under different boundary conditions for near-bed sediment concentration. Comparison among the model and experimental results suggests that the Mellor–Yamada model predicts a damping effect on the eddy viscosity which is similar to the Smith–McLean model, while the k-ε model consistently predicts weaker stratification effects. Based on this result, a modified boundary condition for the k-ε model is then proposed. G.R. Hancock, T.J. Coulthard, and J.B.C. Lowry, 2013. Predicting uncertainty in sediment transport and landscape evolution – the influence of initial surface conditions, Computers & Geosciences, V.90, Part B, 117-130. DOI: 10.1016/j.cageo.2011.12.004

Morphodynamic modeling using the Telemac finite-element system Catherine Villaret, Jean-Michel Hervouet, Rebekka Kopmann, Uwe Merkel and Alan G. Davies

The open-source finite-element system Telemac has been applied to simulate various complex hydrodynamic and morphodynamic situations including waterways, curved channels, recirculating flows and wave-induced littoral transport. In the applications presented here, the sediment transport model is mainly restricted to the transport of non-cohesive sediments, which relies on classical semi-empirical concepts including sand grading effects, parameterization of secondary currents and wave effects. In comparison with other comprehensive modeling systems (Delft-3D, Mike-21, etc.), the main originality lies in the efficiency and flexibility of the finite elements. Thanks to the optimization of numerical schemes, parallelism, as well as tremendous progress in the performance of computers, bed evolution can be calculated on basin scale (10–100 km) and for the medium term (years to decades), without the use of hydrodynamic filtering methods. As a novelty in release 6.0, we present a method of feedback for the bed roughness, which reduces uncertainty in the prediction of both transport rates and flow velocities. Catherine Villaret, Jean-Michel Hervouet, Rebekka Kopmann, Uwe Merkel and Alan G. Davies, 2013. Morphodynamic modeling using the Telemac finite-element system, Computers & Geosciences, V.90, Part B, 105-113. DOI: 10.1016/j.cageo.2011.10.004

A numerical model to develop long-term sediment budgets using isotopic sediment fingerprints Enrica Viparelli, J. Wesley Lauer, Patrick Belmont and Gary Parker

Developing accurate long-term, basin-scale sediment budgets using isotopic sediment fingerprints requires a sediment routing model that not only accounts for a range of sediment source terms (e.g. tributaries, surface erosion and erosion of bluffs and terraces) but also considers the variation in time of volume and tracer concentration for the sediment stored in the floodplain. This is accomplished here using a tracer routing model that accounts for production and decay of radioisotopes in the floodplain. The numerical model focuses on the average (i.e. across many hydrographs or years) budget of sediment and tracers at reach scale. To account for storage and remobilization of bulk sediment and/or tracer material, the model represents the floodplain as a system that can gain or lose mass depending on overbank deposition and net bank erosion rates. Isotopic tracers within the floodplain reservoir can be produced as a function of cosmic ray bombardment or atmospheric fallout, and can decay according to a first-order rate equation. Governing equations are derived using a simplified geometry that treats rivers at reach scale: channel sinuosity and migration rates are user-specified parameters, exchange of sediment and tracers between the river and floodplain is modeled at each cross section, and governing equations are derived in a 1D, width-averaged formulation. When the system reaches mobile equilibrium, the sediment deposited on the floodplain through overbank deposition is balanced by the sediment eroded from the floodplain through channel migration and by sediment contributed from external sources. The model is applied to a generic river system and is shown to converge over time to an equilibrium condition that is consistent with an independent analytical solution. Enrica Viparelli, J. Wesley Lauer, Patrick Belmont and Gary Parker, 2013. A numerical model to develop long-term sediment budgets using isotopic sediment fingerprints, Computers & Geosciences, V.90, Part B, 114-122. DOI: 10.1016/j.cageo.2011.10.003

Taking it to the streets: The case for modeling in the geosciences undergraduate curriculum Karen Campbell, Irina Overeem and Maureen Berlin

The United States faces a crisis in education: a dire shortage of students sufficiently prepared in the STEM (Science, Technology, Engineering and Mathematics) disciplines to competitively enter the workforce (National Education Technology Plan, 2010). At the same time, there is increasing demand for well-trained geoscientists in a variety of careers related to the environment and natural resources. Many efforts, including the recently released Earth Science and Climate Literacy Principles, seek to promote better Earth science education, as well as to strengthen the Earth science literacy of the entire US population. Yet even those undergraduate students who choose to major in geology or related geoscience disciplines rarely acquire sufficient quantitative skills to be truly competitive graduate students or professionals. Experience with modeling, during their undergraduate careers, could greatly increase the quantitative literacy of geoscience majors and help them appreciate the real world applicability of mathematics and computational methods in their future careers in the geosciences. Karen Campbell, Irina Overeem and Maureen Berlin, 2013. Taking it to the streets: The case for modeling in the geosciences undergraduate curriculum, Computers & Geosciences, V.90, Part B, 123-128. DOI: 10.1016/j.cageo.2011.09.006

CarboCAT: A cellular automata model of heterogeneous carbonate strata Peter M. Burgess

CarboCAT is a new numerical model of carbonate deposystems that uses a cellular automata to calculate lithofacies spatial distributions and hence to calculate the accumulation of heterogeneous carbonate strata in three dimensions. CarboCAT includes various geological processes, including tectonic subsidence, eustatic sea-level oscillations, water depth-dependent carbonate production rates in multiple carbonate factories, lateral migration of carbonate lithofacies bodies, and a simple representation of sediment transport. Results from the model show stratigraphically interesting phenomena such as heterogeneous strata with complex stacking patterns, laterally discontinuous subaerial exposure surfaces, nonexponential lithofacies thickness distributions, and sensitive dependence on initial conditions whereby small changes in the model initial conditions have a large effect on the final model outcome. More work is required to fully assess CarboCAT, but these initial results suggest that a cellular automata approach to modeling carbonate strata is likely to be a useful tool for investigating the nature and origins of heterogeneity in carbonate strata. Peter M. Burgess, 2013. CarboCAT: A cellular automata model of heterogeneous carbonate strata, Computers & Geosciences, V.90, Part B, 129-140. DOI: 10.1016/j.cageo.2011.08.026

Polydisperse turbidity currents propagating over complex topography: Comparison of experimental and depth-resolved simulation results Mohamad M. Nasr-Azadani, Brandon Hall and Eckart Meiburg

A computational investigation is presented of mono-, bi-, and polydisperse lock-exchange turbidity currents interacting with complex bottom topography. Simulation results obtained with the software TURBINS are compared with laboratory experiments of other authors. Several features of the flow, such as deposit profiles, front location, suspended mass, and runout length, are discussed. For a monodisperse lock-exchange current propagating over a flat surface, we investigate the influence of the boundary conditions at the streamwise and top boundaries, and we generally find good agreement with corresponding laboratory experiments. However, we note some differences with a second set of experimental data for polydisperse turbidity currents over flat surfaces. A comparison with experimental data for bidisperse currents with varying mass fractions of coarse and fine particles yields good agreement for all cases except those where the current consists almost exclusively of fine particles. For polydisperse currents over a two-dimensional bottom topography, significant discrepancies are observed. Possible reasons are discussed, including erosion and bed load transport. Finally, we investigate the influence of a three-dimensional Gaussian bump on the deposit pattern of a bidisperse current. Mohamad M. Nasr-Azadani, Brandon Hall and Eckart Meiburg, 2013. Polydisperse turbidity currents propagating over complex topography: Comparison of experimental and depth-resolved simulation results, Computers & Geosciences, V.90, Part B, 141-153. DOI: 10.1016/j.cageo.2011.08.030

Driving plug-and-play models with data from web services: A demonstration of interoperability between CSDMS and CUAHSI-HIS Scott D. Peckham and Jonathan L. Goodall

There has recently been an increased focus within the earth science community on integration of data and modeling resources. Two examples of projects in this area are the Community Surface Dynamics Modeling System (CSDMS) and the Hydrologic Information System (HIS) project of the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI). The primary focus of CSDMS is on modeling, specifically on approaches and tools that allow scientists to construct a simulation model as a configuration of linked, interchangeable model components. The primary focus of the HIS is on data, specifically on approaches and tools that allow scientists to easily access and integrate data from different data providers. The synergies between these two projects are obvious as both data and models are needed to support scientific analysis and natural resource management. For this reason, we have explored a means for providing interoperability between the CSDMS and the HIS. In the approach presented here, the HIS web services are used within the CSDMS modeling framework to search and download hydrologic data that can then be easily fed into CSDMS model components. The result of the work is a CSDMS component able to query, download, and provide plug-and-play access to HIS data directly within the CSDMS modeling framework. This approach therefore provides a means for leveraging large sets of scientific data within a sophisticated modeling framework. Scott D. Peckham and Jonathan L. Goodall, 2013. Driving plug-and-play models with data from web services: A demonstration of interoperability between CSDMS and CUAHSI-HIS, Computers & Geosciences, V.90, Part B, 154-161. DOI: 10.1016/j.cageo.2012.04.019