WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: SC3781
Title: Reservoir Shoreline Erosion and Sediment Deposition with Cohesive Sediments
Focus Categories: Sediments, Surface Water
Keywords: cohesive sediments, reservoir circulation, reservoir bank erosion, sediment transport, reservoir sedimentation
Start Date: 03/01/2001
End Date: 02/28/2002
Federal Funds: $24,258
Non-Federal Matching Funds: $51,521
Congressional District: Third
Paul A. Work
Associate Professor, Clemson University
An examination of most large reservoirs reveals numerous erosion areas that become problematic once the erosion begins to encroach on development. Seawalls and revetments are the typical response to the problem and, taken together, represent a large investment, both public and private. The erosion also affects reservoir water quality and useful lifetime. Setback requirements have been used to preserve buffers of land along reservoir shorelines, but the setback distance is typically not site-specific and does not consider spatially varying conditions or physical processes that should dictate larger setbacks in certain areas. Most coastal states now have setback regulations for coastal construction that are site-specific and are based on local, long-term erosion rates.
The proposed project focuses on predictions of shoreline erosion rates on reservoirs featuring cohesive sediments, such as commonly found in the Piedmont region of South Carolina, and the fate of the eroded sediment. A relatively simple numerical modeling approach is employed for erosion predictions, utilizing existing wind, water level, and reservoir geometry/bathymetry data as input to the model. The general procedure is to use the wind data to predict wave heights along the shoreline, and then compute long-term shoreline erosion rates based on local wave energy, water level, sediment type, and shoreline geometry. A comprehensive, three-dimensional, numerical, hydrodynamic model will also be employed to examine circulation and sediment deposition pattern within a reservoir for selected wind and hydrological conditions.
Hartwell Lake, a U.S. Army Corps of Engineers reservoir on the Savannah River, bordering South Carolina and Georgia, is selected as a case study. A previous project by the principal investigator resulted in an inventory of erosion control structures on this reservoir and qualitative identification of several erosion "hot spots" on the lake. The new project will provide quantitative predictions of erosion rates and identify likely sediment pathways within the reservoir. Predictions will be compared to existing erosion rate data, available for two sites on Hartwell Lake, for calibration of model results. The chosen reservoir is also of interest because of a major sediment contamination (PCB) problem. High concentrations of PCBs are found in Twelve Mile Creek, a tributary to Hartwell Lake.