Effects of Climate Change on Stormwater Capture Depths in the U.S. Mid-Atlantic Region

Abstract:

Increases in storm intensity and magnitude affects regional and local scale watershed hydrology and corresponding impacts. Information pertaining to the annual rainfall is valuable in flood mitigation and water quality concerns. The approach of the US Environmental Protection Agency (EPA) to provide onsite detention of various percentile capture depths stormwater management is examined here. Such information is pertinent to construct new or extend current undersized drainage infrastructures with consideration of future high intensity flood events which are anticipated to increase. In this study, the North American Regional Climate Change Assessment Program (NARCCAP) regional climate model (RCM) precipitation baseline (1973-2000) and future (2041-2070) data are used to generate annual 85% and 95% capture depths for Washington D.C.-Baltimore metropolitan area. The RCM data contain systematic biases and are therefore adjusted to produce appropriate estimates at the local scale. Depending on the adjustment technique used, the statistically transformed data leads to increased precipitation capture depths. In this study, several approaches: non-parametric, parametric, and modified parametric methods are employed for bias correction. Graphical comparisons of the adjustment techniques using National Climate Data Center (NCDC) and several model combinations (GCM+RCM) daily rainfall data are presented. Comparisons are made between NCDC daily rainfall and simulated (uncorrected and corrected) data to assess mean absolute error.