| This study investigates the hydrology of the Chapel Branch Creek (CBC), an ∼4000 acre (∼1600 ha) watershed, located adjacent to Lake Marion in Orangeburg County, SC. The watershed is listed on the SC 2004 303(d) list of impaired waterbodies due to elevated levels of nitrogen (N), phosphorus (P), chlorophyll-a, and pH. The study focuses on the validity of two GIS-based runoff modeling methods, the Rational and SCS-CN methods, applied to the CBC watershed to estimate both storm runoff volume and peak runoff rates. The models were each run with the rainfall intensities from three hypothetical design storms and five field-observed storms. Furthermore, in order to test runoff prediction ability, modeling results were compared to observed peak flow rates and runoff volume recorded at sampling location 7 (SL-7), which drains an area of 1441 acres. Application of the SWAT model was also explored and an initial parameterization was carried out for the SL-7 drainage area. Results of this study show that a weighted low C-value (Rational Method) and a weighted Q (SCS-CN Graphical Peak Discharge method) yield the most accurate estimates of peak runoff rate. In addition, estimated Qp rates are more accurate when aggregated by sub-unit than when calculated for the whole SL-7 drainage area. |
