Comparison of Two Stochastic Modeling Approaches for PFHA Development

Probabilistic Flood Hazard Analysis (PFHA) for dam and levee safety is typically conducted using either stochastic rainfall-runoff models or inflow volume-based statistical methods. When flow observations are not suitable, the stochastic rainfall-runoff approach to PFHA is the preferred method. Two widely used tools for performing stochastic rainfall-runoff analysis are the U.S. Army Corps of Engineers (USACE) Risk Management Center (RMC) Rainfall-Runoff Frequency Tool (RRFT) and the Stochastic Event Flood Model (SEFM) developed by MGS Engineering and now owned by RTI. Both stochastic tools employ deterministic rainfall-runoff models while treating hydrometeorological inputs as random variables instead of fixed values. This paper compares the performance of RRFT and SEFM, offering recommendations on when each tool is most appropriate and opportunities for future improvements.