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ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT
Citation:
Hayter, E J., J. M. Hamrick, B. R. Bicknell, AND M. H. Gray. ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-01/072 (NTIS PB2004-101172), 2001.
Impact/Purpose:
Develop, test, and refine models to evaluate sub-basins to determine whether local water quality problems due to excessive nutrient loading exist, and if so, to characterize them and determine their relationships to nutrient loading. Develop models to simulate overland flow and non-point source pollutant loads to track and assess nutrient loadings across watersheds and provide approaches for estimating nutrient budgets within sub-basins and for predicting changes in nutrient budgets in response to changes in watershed activities/land use/land cover. Demonstrate the application of the recommended approach/models for predicting changes in nutrient budgets in response to changes in proposed watershed activities/land use/land cover, resulting in specific recommendations for reducing the nutrient loads to a basin. For coherence, cooperation, and economics, these models will be housed in a unified, consistent, computational environment for environmental analyses that allows teaching (i.e., technology transfer) to multiple users (users concentrate on problem, not model input/output); that appeals to multi-disciplinary groups for distribution and use as a consistent assessment methodology (includes models, tools, modular design and facilitated updates of science/engineering); that includes resident visualization, animation tools, documentation and tutorials on-line, hooks to GIS and environmental databases; and is executable on UNIX, personal computers, and HPC resources.
Objective # 2.2 Conserve and enhance nation's waters: By 2005, conserve and enhance the ecological health of the nation's (state, interstate, and tribal) waters and aquatic ecosystems-rivers and streams, lakes, wetlands, estuaries, coastal areas, oceans, and groundwater-so that 75% of waters will support healthy aquatic communities.
Description:
This technical report describes a new sediment transport model and the supporting post-processor, and sampling procedures for sediments in streams. Specifically, the following items are described herein:
EFDC1D - This is a new one-dimensional hydrodynamic and sediment transport model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. The User Manual is published as a separate report (Hamrick 2001). EFDC1D can simulate bi-directional unsteady flows and has the ability to accommodate unsteady inflows and outflows associated with upstream inflows, lateral inflows and withdrawals, groundwater-surface water interaction, evaporation and direct rainfall. The model also includes representation of hydraulic structures such as dams and culverts. For sediment transport, the model includes settling, deposition and resuspension of multiple size classes of cohesive and noncohesive sediments. The bed is represented by multiple layers of mixed sediment classes. A bed consolidation model is implemented to predict time variations of bed depth, void ratio, bulk density and shear strength. The sediment bed representation is dynamically coupled to the cross-sectional area representation to account for area changes due to deposition and resuspension.
GenScn - The interactive computer program GENeration and analysis of model simulation SCeNarios (GenScn) was modified to read in one of the output files from EFDC1D, namely the "dump1d.out" file. This files contains simulated time series of parameters such as water surface elevation, temperature, salinity, discharge, cross-sectional area and wetted perimeter, concentrations of suspended cohesive and non-cohesive sediment, and average bed shear stress at each computational cell. Time series plots of these parameters can be generated for any computational cell. The modified version of GenScn is also included on the distribution CD.
Another task in this project was to link the EFDC1D hydrodynamic and sediment transport model with HSPF (Bicknell et al. 1997) to provide a more valid flow/sediment transport modeling tool for development of TMDLs in watersheds that experience significant nonpoint source impacts. While complete integration of EFDC1D with HSPF is feasible, it is a task that requires: 1) additional study to determine the advisability and method of integration, 2) additional 1-D model code testing and refinement, and 3) more resources than were available in this effort. As such, a linkage program was developed to reformat the output of HSPF for subsequent input to the stand-alone EFDC1D model. This linkage program is also included on the distribution CD.
To perform sediment transport modeling, a comprehensive set of hydrologic, hydraulic, and sediment data must be collected/measured in the water body to be modeled. A generic field study work plan, including sampling procedures, is given as an example of the type of field study that should be performed to collect these data.