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Assessing vulnerability through storm transposition


Historical climate data for the Midwestern U.S. show substantial regional variability in the occurrence of extreme rainfall events.  Climate projections for the region based on both statistically downscaled General Circulation Models and Regional Climate Models show significant inter-model variability in the magnitude and frequency of extreme rainfall events.  As a result, these climate projections cannot be used alone to adaptively manage water resources in a changing climate.  We believe that storm transposition provides an effective way to evaluate the vulnerability from extreme rainfall and flooding.

We have reconstructed the 2008 storm that caused catastrophic damage across parts of south-central Iowa and Wisconsin.  We are currently using an existing hydrodynamic model of the Yahara Lakes ( to estimate the extent of damage that would have occurred had the storm been centered over the lakes.  Two cohorts of managers and decision-makers are participating in this exercise.  The first includes the public officials with oversight of public works and management functions who influence infrastructure and facility siting decisions.  To date this group has been uniformly enthusiastic about the utility of the approach.  The second group will comprise water resource managers in other communities outside of the demonstration area.  This work is currently supported by a NOAA grant. NECSC support will enable us to extend the use of the reconstructed storm to additional applications.  These will focus on river flooding and urban stormwater flooding.  As in the Yahara River study, we will involve managers and decision makers from the beginning of each application. 
Our most recent application is the use of this transposed 2008 storm to evaluate the efficacy of current state, county, and local stormwater ordinances. In particular, we are evaluating the efficacy of volume control components of the ordinance.  Our results to date point to significant weaknesses in the ordinances.  For example, the state ordinance does not adequately protect against increases in lake flooding as a result of land development. Modeling of the Lake Mendota watershed with the tranposed 2008 storm resulted in a record inflow that would have caused serious flooding. We are working with the City of Madison and Dane County to translate this result into policy, and Alexandra Norpel is investigating large closed depressions in the Yahara River watershed as possible opportunities for preventing increased lake  flooding as a result of climate change.
Application of storm transposition can identify vulnerabilities to extreme storm events, and hence to climate change.  The specific findings of this study will inform local decisions, as well as demonstrate the efficacy of the storm transposition method.  Nick Hayden is using storm transposition to evaluate the effectiveness of state and local stormwater ordinances for preventing increases in storm runoff volumes resulting from urban and suburban development. Dane County engineers are using our transposition results to explore operating policies for the control structures on the upper lakein the Yahara chain of lakes.


Annual meeting AWRA, 2016.
Webinar: 2014,“Climate Information for Managing Risks In Water Resources.” Sponsored by NOAA Sectoral Applications Research Program (SARP), US National Integrated Drought Information System (NIDIS), Water Research Foundation, Water Environment Federation (WEF), Water Environment Research
Liebl, D., City of Madison Common Council, Organizing a city-wide climate adaptation plan that would result in Madison becoming a Climate Ready Community. February 2015. Video link
Annual meeting of WAFSCM, 2014.
Northeast Climate Science Center, November 2014, "Transposing Extreme Rainfall to Assess Climate Vulnerability", K. Potter, D. Liebl.
UCOWR/NIWR/CUAHSI Annual Conference, "Storm Transposition: A New Use for An Old Method". 2014.
Annual meeting of WAFSCM, 2013.
Annual meeting of the Wisconsin Association of Flood, Stormwater, and Coastal Management (WAFSCM), 2012.
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