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2024 EWRI Congress

2024 Symposium on Hydro-climate and Climate Change (Watershed)

Impacts of a Changing Climate on Hydrologic Design

260 - Process-based Flood Frequency Analysis: A Key to Unlock the Impacts of Climate Change on Floods

Tuesday, May 21, 2024
1:00 PM – 1:15 PM CT
Room: S 103 B
Flooding is a complex process influenced by atmospheric forcings—primarily precipitation—and the antecedent conditions of the watershed where precipitation falls. In nonstationary conditions such as climate change, the fundamental physical processes governing flooding may undergo changes: climate change can alter precipitation patterns, as well as watershed antecedent conditions including soil moisture and snowpack. Therefore, to understand how climate change will impact floods, we should consider the combined effects of changes in precipitation patterns and changes in watershed antecedent conditions. The statistical analysis of streamflow observations, while a common approach in Flood Frequency Analysis (FFA), falls short in providing insights into the evolving dynamics of flood causes. Process-based FFA, as an alternative, is a tool for deciphering how the evolution of individual and joint flood causative factors impact flood of different magnitudes and likelihoods. The objective of this study is to analyze the influence of climate change on flood characteristics by quantifying the integrated impacts of changes in climate and antecedent conditions using a process-based flood frequency approach. We calibrate WRF-Hydro hydrologic model using “Fusion,” a nationwide meteorological forcing dataset developed at the University of Wisconsin–Madison. We apply WRF-Hydro to CONUS404 convection-permitting historical and future climate simulations to generate long-term watershed antecedent conditions. Then we conduct a large number of event-based hydrologic simulations by coupling realistic precipitation scenarios generated by stochastic storm transposition with seasonally appropriate antecedent conditions to do flood frequency analysis under a changing climate. We apply the methodology to the Kickapoo watershed in southwest Wisconsin.