Defining Predevelopment Hydrologic Reference Conditions in North Carolina, USA: Preliminary Results

Abstract. Urbanization and land development have altered natural hydrology. Various methods of stormwater management have been used to control excess surface runoff. Low impact development (LID) is a new method of land development designed to manage stormwater in a way that mimics natural hydrology. Previous research studies have demonstrated that the stormwater management ability of LID is more effective than conventional land development; however, most studies are unable to compare LID to predevelopment hydrology. The goal of this study is to define predevelopment hydrology, to be used for future evaluation of LID implementations. Predevelopment hydrology will be defined for the three physiographic regions of North Carolina: Coastal Plain, Piedmont, and Mountain. A study site is located in each of the three regions, monitoring precipitation and surface runoff for at least one year. Data will be processed and analyzed in various ways to create the predevelopment hydrologic reference conditions. For instance, runoff coefficients, runoff threshold, and other cumulative statistical computations can be set as the natural hydrologic reference. Also, a flow duration curve for each site will be created. A flow duration curve has the ability to reveal valuable information in an easy to understand graphical format, and could be used as a robust evaluation method for future low impact developments. The results presented in this paper are only preliminary, as the study is ongoing.