Storm Transposition- a Tool for Climate Change Adaptation

Abstract:

For much of the world, climate models predict significant increases in the magnitude and frequency of extreme rainfalls. As a result communities are being encouraged to identify and reduce their vulnerability to extreme rainfalls. However, climate model projections of precipitation vary greatly across models. While there exist strategies for accommodating uncertainties in climate model projections, for various reasons seems unlikely that state and local governments will use any of them. For communities that have not experienced extreme storms in recent memory, useful information on their vulnerability can be obtained by hydrologic modeling based on high-resolution rainfall data from one or more extreme storms that have occurred elsewhere in the region. This approach, called storm transposition, was developed in the early 20th century when hydrologic times series were relatively short, and is still used today to estimate Probable Maximum Flood discharges for designing emergency spillways for hazardous dams. We present examples of the use of storm transposition for evaluating extreme rainfall vulnerabilities in Dane County, Wisconsin. Our findings suggest that state and local decision-makers are very receptive to using this approach to anticipate and adapt to impacts from extreme rainfall events.