207 - Shifted Flood Frequencies in the Mid-Atlantic US: Insights from Downscaled CMIP6 Hydroclimate Projections

Due to climate change, the magnitude and frequency of extreme rainfall events are projected to increase in the future. This will have wide-ranging implications, including flooding that affects agriculture, dam safety, population well-being, and energy security. This study employs a multi-model ensemble modeling approach within an uncertainty framework to assess changes in flood frequency in the Mid-Atlantic region of the United States, which is one of the most frequently affected regions by flooding from extreme weather events. Global climate projections from the state-of-the-art Climate Model Intercomparison Project Phase 6 (CMIP6) are downscaled and bias-corrected using both dynamical and statistical approaches. These downscaled projections are then employed to drive two calibrated hydrologic models, Variable Infiltration Capacity (VIC) and Precipitation-Runoff Modeling System (PRMS), to simulate their runoff response. Streamflow routing is accomplished using a high-resolution river network and an efficient routing model, RAPID, to produce ensemble streamflow projections for both the 1980–2019 baseline and 2020–2059 near-term future periods considering multiple emission scenarios. Multiple commonly used probabilistic distributions are fitted to annual streamflow maxima to derive projected flood frequency estimates along with their associated uncertainties. These estimates can support comprehensive flood risk assessments, and can inform decision-making for multi-sectors such as climate-resilient agriculture (e.g., planting perenials), hydropower (e.g., dam safety), and other critical infrastructures.