Floods have been occurring with an increasing frequency resulting in damage to communities across the globe. These impacts are expected to continue to rise in the future due to increases in precipitation intensity for extreme rainfall. Global Climate Model output, imperfect as it is in reproducing daily rainfall, is the only practical source of future projections of extreme rainfall intensification. This article presents a method that addresses the inherent difficulty in translating GCM precipitation output into usable outputs for stormwater and flood management planning on a regional or local level. The method makes use of available runoff estimates from GCM precipitation and Variable Infiltration Capacity models to estimate changes in the impacts of extreme storm intensification by watershed as well as a method for estimating changes to riverine flooding elevation and frequency due to climate change. It provides communities and utilities with an approach to obtain a screening-level estimate of climate change impacts to peak discharge rate statistics without conducting hydrologic modeling. This presentation outlines the method and its implementation for the 48 contiguous States of the USA.
