Historical and Projected Extreme Snow Accumulation and Melt Events for Infrastructure Design using the NA-CORDEX Ensemble of Regional Climate Models

Snowmelt is a dominant driver of flood generation in regions with seasonal snow-cover. Recent snowmelt floods in 1997, 2009, 2011, and 2019 in the north-central and north-eastern U.S. had large societal and economic impacts on communities. The current engineering practice provides very limited guidance on designing infrastructure to accommodate snowmelt driven floods using the historical data and no guidance regarding how to consider a non-stationary climate. Future designs are particularly critical because the changing climate is well understood to change winter temperature and precipitation regimes in a manner that will alter the characteristics of flooding. In this study, trends and designs of extreme 25- and 100-year snow water equivalent (SWE) and snowmelt events are quantified in the mid and late 21st century using the North America - Coordinated Regional Climate Downscaling Experiment (NA-CORDEX) ensemble of regional climate models under Representative Con-centration Pathways 8.5 (RCP 8.5). The future designs of extreme SWE and snowmelt will be compared with the current designs developed by using the SNOw Data Assimilation System (SNODAS) and University of Arizona (UA) SWE data sets over the continental United States. The results are expected to provide the guidance needed to add flood risk factor driven by snowmelt events under a changing climate to North American infrastructure standards.