Towards Impact-Informed Dam Safety Risk Assessment: Understanding the Shift in Flood Hazards and Uncertainties across the Conterminous US

Abstract Submission: The magnitude and frequency of extreme weather events are projected to intensify in a changing climate with wide-ranging implications, including flooding that may impact dam safety, population well-being, and energy security. Notably, change in extreme streamflow are expected to be inconsistent and non-homogeneous across the Conterminous US (CONUS), raising the level of difficulty for risk prioritization and emergency preparedness. To provide insights into the regional differences, this study employs a multi-model, uncertainty-aware modeling framework to assess shifts in flood frequences across ~2.7 million CONUS NHDPlusV2 river reaches, including the hydropower dam locations. The framework uses downscaled (statistical and dynamical) and bias-corrected (with Daymet and Livneh) global climate model outputs from the Climate Model Intercomparison Project Phase 6 (CMIP6) to drive two calibrated hydrologic models, Variable Infiltration Capacity (VIC) and Precipitation-Runoff Modeling System (PRMS). Simulated total runoff is then routed through the river network using the RAPID routing model to project streamflow through the end of the century under multiple emission scenarios. We first develop conventional flood frequency estimates under the stationary assumption, using multiple probabilistic distributions and characterizing their uncertainties with a simple and effective analysis of variance (ANOVA) approach. Alternative non-stationary methods are also employed to address the changing dynamics of climate, land use land cover, and socio-economic factors. A proof-of-concept demonstration is provided for selected hydropower reservoirs across CONUS, highlighting the diverse impacts, including the disproportionate level of damages to the disadvantaged communities, facing these dams. The information will serve as a foundation for a large-scale, impact-informed dam safety risk assessment framework and support decision-making across multiple sectors, including dam owners and managers.

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