Reclamation’s Revised Empirical Method for Estimating Life Loss Due to Dam Failure

The U.S. Bureau of Reclamation estimates life loss resulting from dam failure in support of dam safety risk analysis. To estimate life loss, Reclamation has primarily used an empirical methodology that is tied to the interpretation of case histories of dam failures and other types of flood disaster events. The method used by Reclamation since 1999 has been revised and the case history database has been substantially expanded. Case histories are the basis for data points that are used in the estimation of fatality rates. The number of case histories has increased by 50 percent for this update, and 79 data points have been developed with some cases containing multiple points. Reclamation’s revised methodology uses a graphical approach for the selection of fatality rates based on ranges of DV (flow depth multiplied by velocity) and warning time. DV is used to quantify the intensity of flooding and can be related to lethality. The Reclamation Consequence Estimating Methodology (RCEM) is in many ways similar to Reclamation’s previous method, DSO-99-06. However, the RCEM requires greater application of judgment when selecting fatality rates. This article provides an overview of the RCEM procedure, and highlights some key case histories that support the empirical methodology.

Dam failure/flash flood case studies: St. Francis, CA - 1928; Laurel Run, PA - 1977; Big Thompson, CO - 1976; Baldwin Hills, CA - 1963; Big Bay, MS - 2004.