Two-dimensional Sediment Transport Modeling in Cache Creek Settling Basin, California

The Cache Creek Settling Basin (CCSB) is subject to inflows with high sediment concentration. Originally designed to protect the floodway capacity in the Yolo Bypass, current performance of the CCSB is in question following over 70 years of high sediment loads. Operation plans dictate that alterations be made to the levees and/or overflow weir in the basin when trap efficiencies are less than 30 percent. CCHE2D model, a 2D depth averaged hydrodynamics and sediment transport model, is applied to simulate the sediment transport process in the CCSB. Simulations are performed to evaluate the trap efficiency in the basin under current bathymetric conditions. Possible alternatives, such as raising the overflow weir, and removing portions of the levee, are also evaluated. Recent and historical flows and sediment loads are simulated. Preliminary modeling results are presented here.