Stormwater Management in a Changing Climate: Managing High Flow and High Water Levels in Wisconsin
Climate change in Wisconsin is likely to increase the severity and frequency of high flows and high water levels. Our analysis of downscaled climate projections suggest that Wisconsin precipitation is trending toward wetter conditions and more intense rainfall. Climate models also predict increases in cold season precipitation and increases in the ratio of rainfall to snowfall, potentially increasing the frequency of damaging flooding from rivers, lakes, and groundwater. As a result of these changes we expect increases in the magnitude and frequency of high flows in streams and rivers, and high water levels in streams, rivers, lakes and impoundments Engineers have traditionally used historical precipitation and runoff data to design and evaluate infrastructure to manage the risks associated with precipitation to acceptable levels Unless we modify the planning, design and management of this infrastructure to account for climate mediated changes in precipitation, we will face greater than expected damages from high flows and water levels. This is the first written report of the Wisconsin Initiative on Climate Change Impacts (WICCI) - Stormwater Working Group. Members of this group include engineers, planners, utility operators, local government officials, state regulators, and academic researchers. This report provides background on the design of infrastructure and management practices used to manage high water conditions, discusses potential changes in Wisconsin climate based on historical data and downscaled climate model results, and presents specific adaptation strategies that recognize the large uncertainties in climate predictions.