 | Flood Risk Management and the American River Basin: An Evaluation (1995)
Sacramento, California and its surrounding metropolitan area face a significant flood risk from the American River, which flows through the city. Although there is consensus that action is needed to reduce the level of risk, agreement on the appropriate strategy has eluded national, state, and regional decisionmakers. The National Research Council's Committee on Flood Control Alternatives in the American River Basin was established to review the Corps of Engineers investigations of flood control options for the American River basin. This 1995 WSTB report offers findings and recommendations specific to the Corps planning process as applied to the American River basin, as well as broader comments on the nature of
flood risk assessment and its application nationwide. Findings and recommendations presented in the report relate to (1) the identification and evaluation of alternatives, (2) environmental
issues, (3) risk methods, (4) flood risk management behind levees, (5) risk communication, and (6) water resources planning and, decisionmaking.
The report also includes discussion of other key issues. For example, with regard to the proposed Auburn Dam, the report refrains from judging whether construction of a dry dam at the Auburn site is the best approach to reducing Sacramento's flood risk. However, the report recommends that if a dry dam is built it must contain operational gates to ensure management flexibility, protect public safety, and minimize environmental impacts. The report also notes that the CorpsÂ’ risk and uncertainty procedures are innovative and timely, as explicit recognition of modeling uncertainty should result in a better understanding of the uncertainty of flood risk and damage reduction estimates. The report does express reservations, about specific ways in which uncertainty is currently represented and included in the calculation of average flood damages and the residual risk of flooding.
The fundamental question in the American River planning process is how to reduce flood risk in the lower American River basin given a decisionmaking arena that includes significant scientific uncertainty and organized opposition to some of the possible, risk reduction alternatives. The report discusses uncertainties that confront floodplain managers and offers recommendations in many areas, including the need for additional research in some areas. But decisionmakers, agency officials, and interest groups reading this report should not use calls for additional research as an excuse for not taking action. The report notes that scientists and engineers can and should provide careful analyses and interpret the information so it is available to support decision makers, and they should be frank about uncertainties and risks. But the decision to be made should ultimately reflect more than technical factors; it should reflect economic considerations and value judgments pertaining to the appropriate use of natural resources, public monies, acceptable levels of risk, and willingness to accept constraints on land use. The final decision on these issues rests with the public and the political officials who represent them.
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