The Sacramento Area Flood Control Agency (SAFCA) planned to increase flood protection in the Natomas area of Sacramento by raising, strengthening, and lengthening a levee along Dry / Robla Creeks. This project was to be a component of a larger federally-funded project. In the interest of time, SAFCA elected to move ahead with construction and then seek reimbursement from the Corps as a part of the cost-sharing agreement.
SAFCA asked us to estimate inundation-reduction benefits associated with various levee heights and configurations, so that they could appeal to the Corps for reimbursement.
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To provide this information, we inventoried floodplain structures, created a structure database, integrated hydrological and hydraulic information, and used the Corps' risk-and-uncertainty (R&U) analysis to compute the expected annual damage (EAD) and to characterize the level of risk for with- and without-project conditions. In this R&U analysis, we included descriptions of the uncertainty in stage-frequency and in geotechnical behavior. We worked closely with SAFCA's geotechnical consultant to characterize the latter.
We prepared a technical report consistent with the requirements spelled out in Corps guidance, thus facilitating SAFCA's application for federal cost sharing.
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