An analysis of the impact of climate change on urban drainage design storms

The anthropogenic effects imposed on climate in recent history shows changes in extreme precipitation events and the patterns in which precipitation occurs. With future greenhouse gas loadings predicted by the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), the change in precipitation for the future may have very drastic consequences for flood control and water management for municipalities with existing infrastructure. The changes will also have an impact on the methods and techniques on how flood control and management practices will be conducted in the future.;Here, the future extreme (low frequency) events of daily precipitation from the IPCC AR4 General Circulation Models (GCMs) are estimated using Log-Pearson Type III extreme value distribution. Future predictions for twenty year periods surrounding and preceding 2050 and 2100 are compared to current climate predictions from each GCM to find the variability in possible relative change for extreme daily events. The relative change is found for 21 US cities with large populations or significance to this study. A more in depth look at the cities of Aurora, Colorado and Somerville, Massachusetts is done to observe not only the change in extreme daily events but also if seasonal shifts and the variability in extreme events predicted for the future.;For the 21 cities of interest, there is a strong trend that the median value of relative change in daily precipitation for the 10-year and 100-year events goes up in both 2050 and 2100 for all of the cities. In all instances the variability of future events is very large. In both Aurora, CO and Somerville, MA, the absolute change shows that there are no seasonal shifts in daily precipitation. The most conclusive result is that which is already known, that the results for future climate show a great variability and essentially become hard to use for flood control or water managers.