Risk Management Center-BestFit

UP TO $1 MILLION TOTAL SAVINGS IN DAM SAFETY EVALUATION STUDIES

For risk assessment of dams and levees, the probability of failure is always conditional on the magnitude of hydrologic loading or the mass of water stored in the environment. Therefore, it is imperative to determine credible estimates of exceedance probabilities of extreme floods that could lead to failure. Design floods for most dams and levees have return periods of 1:100 or less frequent. High hazard dams are designed to pass the Probable Maximum Flood, which typically has a return period of 1:10,000 or less frequent.

PROBLEM: Most projects in the U.S. have limited flood information, with most sites having fewer than 100 years of gauged flow data. Consequently, the greatest source of error in return period and estimates in a flood frequency analysis is often inadequate data. In order to reduce uncertainties in the estimated probability of occurrence for extreme floods, it is important to incorporate as much hydrologic information into the frequency analysis as possible.

SOLUTION: The Corps’ Risk Management Center (RMC) collaborated with ERDC to develop RMCBestFit to enhance and expedite flood hazard assessments. The software employs a Bayesian analysis framework for combining limited atsite flood data with temporal information from historic and paleofloods; spatial information from regional precipitation frequency and regional skew analyses; and causal information on flood processes.

IMPACT: The Corps can now achieve accurate flood hazard assessments with significantly less time and effort. By including more hydrologic information, RMC-BestFit provides more accurate estimates of design flood return probabilities, which will reduce the chances for over- or under-design and improve overall dam safety investment decisions. Meanwhile, using RMC-BestFit can result in total annual savings of $500 thousand to $1 million across the Corps in dam safety evaluation studies.