Overview of Innovative Life-Risk Analysis Method for the 2012 California Central Valley Flood Protection Plan

Abstract

The State of California’s 2012 Central Valley flood protection plan (CVFPP)—a large-scale reconnaissance-level assessment of flood management problems and potential solutions—formulated a set of broad management alternatives and compared them by assessing risk reduction attributable to each. Both economic risk and life risk were assessed and compared. Economic risk was evaluated with standard U.S. Army Corps of Engineers methods and software. Inputs that described the flood hazard, flood-management system performance, property exposure, and vulnerability to damage were developed by the California Department of Water Resources (DWR) using state-of-practice models (hydrologic, hydraulic, geotechnical, and economic) and data. After considering life-risk analysis methods proposed in the literature, for the CVFPP reconnaissance-level analysis, DWR developed and applied an innovative method that leveraged the economic-risk analysis method and its inputs. Measures of hazard and performance remained the same as for the economic-risk analysis, but exposure in the floodplain was expressed in terms of population at risk, and vulnerability was expressed as a relationship between hazard and life-loss. The new analysis yielded a description of risk in terms of probability of various magnitudes of life-loss, which could be integrated to estimate an expected value. Although approximate, the method provided systematic, repeatable, timely estimates of life-risk for a variety of alternatives considered, allowing fair comparison of the management alternatives for high-level planning studies. However, this method can only broadly support real-time emergency response decision making and other activities that require more detailed conceptual accounting of complex flooding and human response.