Sediment Yield Investigation and Method Comparison for Southern California Coastal Watersheds

The U.S. Army Corps of Engineers, Los Angeles District, and the Office of Water Resources of Marine Corps Base Camp Pendleton contracted with WEST Consultants, Inc. (WEST) to perform watershed analyses of three small coastal basins on the base in southern California. Although this project included hydrologic, hydraulic, and sediment yield studies, the focus of this paper will be the sediment yield estimates. Using subbasin delineations developed for the hydrologic modeling, and extensive geographic information system (GIS) data sets, WEST estimated the amount of sediment yield for these watersheds using four different methods: (1) U.S. Army Corps of Engineers, Los Angeles District (LA Corps), (2) Modified Universal Soil Loss Equation (MUSLE), (3) Dendy and Bolton, and (4) Taylor. Each of the above methods was developed at a different time for slightly different purposes using different input parameters. A brief review of the different methods is provided before results from the different methods for the various subbasins are compared. Sensitivity of the various methods to certain input parameters is explored and recommendations are made regarding the methods presented.