Evaluating design criteria for high hazard dams in a changing climate

With changes in climate, there is the potential for future flooding events to vary in frequency and magnitude. These changes may stress the 432 high hazard dames in West Virginia. The 100-year flowrate is an important design criterion for emergency spillways of high hazard dams. Emergency spillways are designed to be reached only by 100-year flow and above. This work quantified how changes in the 100-year flowrate may affect emergency spillway activation. Peakflow data from the Central Appalachian Ecoregion in WV, taken from 24 USGS gages, were used to analyze changes in the 100-year flowrate. Flow frequency analysis revealed that for unregulated gages, 100-year flow consistently increased, but for regulated gages, 100-year flow consistently decreased. Reservoir routing was completed at a high hazard dam in Greenbrier County under potential future flow scenarios altering peak inflow (-7%, +6%, +12%, +20%, and +30%). The spillway of the dam was predicted to be reached by approximately a 12% increase in 100-year flow, which was matched and exceeded by historical increases in 100-year flow from unregulated gages of up to 19%. These results suggest that emergency spillway designs need to consider potential changes in 100-year flow