Improved Storm Duration and Antecedent Moisture Condition Coupled SCS-CN Concept-Based Model

The Soil Conservation Service curve number (SCS-CN) method is a well-recognized technique for the estimation of direct surface runoff from a rainfall event. Most of the recently developed SCS-CN–based models including the original one ignore the effect of storm duration or rainfall intensity on surface runoff, an important aspect of the rainfall-runoff model. Some of these models have, however, included the antecedent moisture conditions. In this study, storm duration is incorporated in a recently modified version of the SCS-CN method to derive a more advanced model. This version is found to perform generally better than the other on the data of 60 small U.S. watersheds. The former model performed significantly better than the latter on the watersheds dominated by silty soils and cultivated land uses.