Hydrologic Hazard Curve Estimating Procedures

This report summarizes Reclamation’s Flood Hydrology Group’s approach toward developing hydrologic hazard curves for use in evaluating dam safety issues. It recommends that the approach for developing hydrologic hazard curves consider the dam safety decision criteria, potential dam failure mode and dam characteristics, available hydrologic data, possible analysis techniques, resources available for analysis, and tolerable level of uncertainty. Dam safety decision criteria determine the probabilistic range of floods needed to address hydrologic issues. The potential dam failure mode and dam characteristics impact the type of hydrologic information needed to assess the problem. The approach chosen to answer specific hydrologic issues should consider a tolerable level of uncertainty. To reduce the uncertainty in the estimates, additional data collection and use of more sophisticated solution techniques may be required. Three case studies, Los Banos, Fresno, and A.R. Bowman Dams, are presented in the report to illustrate the variety of methods available. These sites were chosen to demonstrate the use of the initial characterization of the flood hazard and more detailed followup studies, where available.