Application of stochastic storm transposition for hydrologic modeling in the mountainous western US

Abstract Recent studies have shown that stochastic storm transposition (SST) is an effective method for flood frequency analysis in small to medium sized watersheds. The effectiveness of this method has not been evaluated in larger watersheds in mountainous regions where snowmelt is the primary driver for peak flow events. In the western United States, several watersheds fall in an area where NOAA Atlas-14 precipitation frequency estimates do not exist. This data sparsity limits the available methods for developing flood frequency estimates. In this research, we present a case study for exploring the use of SST in the high desert of Wyoming, with challenges of scale, regulation, and snowmelt. Building on existing methods, a framework for performing SST in cold mountain regions is proposed, including incorporation of snowmelt functions, normalization fields in high altitude locations, and techniques for hydrologic model adjustment to account for epistemic uncertainty due to regulation. Results show that the foundational processes in the SST framework provide a valuable alternative for peak flow analysis in locations where frequency-based precipitation is not available.