Sacramento, California, is protected from Lower American River (LAR) flooding by a system of levees. These levees block the local natural drainage into the LAR, so Sacramento County operates and maintains an interior drainage system which collects and pumps or drains water into the LAR, as illustrated below. The effectiveness of the interior drainage facilities is affected by the stages in the LAR downstream of Folsom Reservoir. In 1995, the Corps of Engineers proposed to change the flood operation policy for Folsom Reservoir, thus increasing LAR stages. The County was concerned that the changes would affect the performance of their interior drainage system.
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To determine the impacts of operation changes, we developed hydrologic, hydraulic, and system performance models of all the contributing catchments, channels and pond, pumps, and gravity outlets, using HEC-1, HEC-IFH, PRECIP, HEC-RAS/HEC-2, and UNET. We simulated system performance for a 40-year period-of-record, with and without the proposed reservoir operation changes. We used HEC-DSS and various HEC-DSS utilities to manage the large volume of data. With the results of the simulation, we estimated stage-duration-frequency functions, with and without the operation modifications.
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