STORMWATER MANAGEMENT IN A CHANGING CLIMATE: ASSESSING VULNERABILITY THROUGH STORM TRANSPOSITION

It has been predicted that increasing concentrations of greenhouse gases in the atmosphere will increase the magnitude and frequency of extreme rainfall events in the Upper Midwest. This talk focuses on local to regional management of extreme rainfall events, and in particular on adaptation of existing stormwater management strategies to an increase in extreme rainfall events. To assess the vulnerability of current management strategies we make use of storm transposition, which explores response to an extreme rainfall by reconstructing a regional storm and applying it to the system of interest. This analog storm strategy avoids the uncertainties associated with the prediction of precipitation extremes by global circulation models. A case study of the Lake Mendota watershed that transposes the nearby June 2008 storm shows that strengthening infiltration ordinance requirements helps to limit increased runoff from developed areas during an extreme storm. However, as any increase over pre-development runoff may be enough to exacerbate lake flooding during extreme storms, tighter controls of runoff volumes may be needed to counteract the combination of continued urbanization and a wetter climate.