Developing a Stage Frequency Curve Based on Regional Precipitation Frequency Estimates

ABSTRACT ONLY - Many of the dam safety decisions are primarily informed by risk. A key component of the risk estimate is a flood hazard curve, which estimates the annual exceedance probable of an inflow volume or stage. Historically, higher stages with infrequent annual exceedance probabilities include a large amount of uncertainty due to limited records for streams in the drainage area. Incorporating regional precipitation frequency information into reservoir inflow volume or stage frequency calculations can reduce the uncertainty associated with remote annual exceedance probabilities. The U.S. Army Corps of Engineers Risk Management Center (RMC) has developed the Rainfall-Runoff Frequency Tool (RRFT), which is a cloud-based application that provides the ability to quickly perform stochastic rainfall runoff analyses using regional precipitation information to develop or help inform the inflow volume and stage frequency curves. A case study illustrates the RRFT process using NOAA Atlas 14 regional precipitation frequency information to develop the volume frequency and stage frequency curves. The RRFT results are compared with RMC-BestFit, which uses a Bayesian framework to estimate the volume-frequency curve, and RMC-RFA, which estimates the stage-frequency curve using the volume-frequency curve as the main input. The RRFT results showed the top of dam is less frequent than what was model by RMC-BestFit and RMC-RFA.