Location: Watershed Physical Processes Research2013 Annual Report
1a. Objectives (from AD-416):
1. Improve the capability, accuracy and efficiency of computational modeling technology and methodology to better predict the free surface flow associated with physical processes, e.g. complex flows over irregular and varying topography resulting from storms, levee breaching and dam failure. Research includes the upgrading of recently developed NCCHE-models to: 1a. simulate free surface flows more realistically; 1b. enhance the computing speed for simulating flows in larger regions for longer time; and 1c. provide better GIS-based data management and scientific visualization/animation tools. 2. Integrate the improved free surface flow models with the erosion and sediment transport models to quantify and predict ephemeral gully development, dam and levee breaching, and sediment relocation and control during dam removal or failure. Research includes: 2a. improving and modifying the existing models for simulating erosion, sedimentation and morphologic processes. These models were developed by NCCHE for specific applications, such as in-stream processes in drainage networks of agricultural watersheds, embankment erosion, levee/dam breaching, sediment relocation control in dam rehabilitation or removal, etc; and 2b. developing user-friendly software packages for research scientists and field professionals to solve agricultural problems in conducting their projects. 3. Develop and upgrade models to better predict the movement and dispersion of agricultural contaminants and their interactions with the sediment and bed materials in surface water systems. Research includes: 3a. improving and modifying the contaminant transport model for environmental impact assessment applications, and 3b. developing user-friendly software packages for research scientists and field professionals working on agricultural watersheds. 4. Integrate and improve decision support systems for watershed management that are reliable, computationally efficient, readily usable, and transferable. Research includes: 4a. updating existing file interface, coupling CCHE1D and AnnAGNPS models and porting the CCHE1D graphic interface to ArcGIS platform to ensure full GIS capability, and 4b. upgrading and enhancing the existing GIS-based decision support system for integrated watershed management by (1) adding coupled CCHE1D and SWAT/APEX modeling capability, (2) implementing the capability for automatic watershed model generation and automatic input data preparation for field scale ephemeral gully erosion by querying USDA-NRCS databases and other data sources, and (3) implementing a module to minimize morphodynamic effects in drainage networks by optimizing sediment control and management with novel nonlinear optimization techniques.
1b. Approach (from AD-416):
The research approach is common to all four research objectives and is designed to (1) systematically increase the models’ capabilities of simulating the physical processes, (2) rigorously and comprehensively verify and validate the newly improved models, and (3) develop the application of software for specific agricultural applications in collaboration with research scientists and/or field professionals. Emphasis will be placed on the release of mathematically verified and physically validated computational models to research scientists for advancing the basic knowledge of physical processes and to professionals for scientifically predicting the outcome of planned practices. Computational modeling technology will be routinely advanced to meet increasing demand as called for.
3. Progress Report:
The National Center for Computational Hydroscience and Engineering (NCCHE) developed a 3-dimensional finite volume method to simulate dam-break flow. This volume-of-fluid (VOF) method handles rapidly changing free surface flow and was tested on several hydrodynamic cases. This technology is very useful for Action Agencies like the Natural Resources Conservation Service (NRCS), the Department of Homeland Security, and the U.S. Army Corps of Engineers, when life and property is threatened. The CCHE2D model was improved by using refined computational meshes, with quadrilateral and triangular elements. Several experimental data sets were used to validate the improved CCHE2D model. This technology is very useful for describing and predicting complex flow regimes in stream systems. Technical manuals have been prepared for the updated versions of the CCHE2D and CCHE3D flow simulation models that make it possible to use them for various applications, such as flood and dam-break simulations, mapping and simulating stream/river bank erosion processes, local scouring, pollutant and sediment transport in water quality simulations. A simplified version of an embankment failure model was developed for simulating dam/levee breaching processes in cases of overtopping and failure by piping. The model has been validated with 50 data sets from laboratory experiments and field case studies. The CCHE2D model and the ARS dam break model, WinDam, were combined, thereby expanding their applicability potential. A new scouring calculation scheme based on turbulent energy dissipation in local scour in the CCHE3E model was developed and tested using several data sets obtained in laboratory and field studies. In testing the model, the physical data required were collected under unsteady flow and non-uniform conditions of supercritical flow. The simulations showed good agreement with observed scour relative to shape, depth, and time evolution. CCHE2D was improved to capture detailed patters of channel incision in the upstream area and sediment aggradation in the downstream part of the channel following dam removal. CCHE2D and CCHE3D have been improved to predict spatial temporal water quality affected by the movement and distributions of phytoplankton and dissolved oxygen in Mississippi lakes. The improved models indicated the ability to simulate complex and interactive processes such as flooding, sediment movement, salinity changes, and water quality adjustments. In the improved versions of CCHE2D and CCHE3D the Graphical User Interface was modified and updated to run water quality simulations in a user-friendly environment and to visually analyze directly the results of water quality simulations.