Publication Information

Hydrological studies in the Southeastern U.S. have primarily focused on runoff generation processes in Piedmont and mountainous areas; much less is known about the relevant processes in Coastal Plain watersheds. Hydrologic processes between these two areas may differ considerably due to climate, topography and soil composition. Because of the population growth and subsequent development in the last few decades in the Lower Coastal Plain (LCP) of South Carolina (SC), it is important to understand natural hydrologic processes in the LCP for predicting hydrologic impacts of land management activities and designing Best Management Practices (BMPs). Past and current research and monitoring efforts by the US Forest Service and collaborators on protected lands within the Francis Marion National Forest (FMNF) in the LCP, 53 km northeast of Charleston, SC provide excellent opportunities to interpret hydrological processes such as rainfall-generated runoff under well-studied and controlled conditions.
This study describes relationships between seasonal rainfall patterns and stream flow for a third order watershed, Turkey Creek, using ten years of historical rainfall and stream flow data (1964 1973). Storm event runoff-rainfall ratios were used to describe baseline runoff as a function of season and rainfall amount. It was hypothesized that runoff-rainfall ratios are smaller during the summer season and greater in the winter due to generally reduced flows as a result of increased evapotranspiration (ET) from the forests during summer-fall, and saturated soils with sustained flows in winter-spring. Alternatively, runoff-rainfall ratios may be directly proportional to the antecedent soil moisture condition (as estimated by rainfall amount during the 5 and 30 days preceding the storm event). Results showed statistically significantly (p = 0.01) higher runoff rainfall ratios for storms occurring during wet antecedent conditions than for dry antecedent conditions.