Theory-Based SCS-CN Method and Its Applications

This study, by incorporating the Philip infiltration solution, constructs from a theoretical perspective an alternative model to replace the Soil Conservation Service curve-number (SCS-CN) method and provides an in-depth analysis of its variants in order to understand their limitations and accuracy. Variants under analyses include the nonlinear I(a)-R relation of Jain et al. and the general and modified Mishra-Singh models which, in spite of favorable consistency with observed data, are obtained by approximation, leaving several odd results unexplained. Along with the crucial assumptions embedded in the SCS-CN method, vital factors dominating model accuracy are examined at constant rainfall intensity. Soil-infinite storage is avoided to reflect the actual situation in most vadose zones, which amends the SCS method and allows the theoretical exploration of the range in which CN usually falls. Using different soils, this study compares the differences and common features of all the models in order to test their proficiency. Finally, the features of a unit hydrograph are integrated into the alternative model to perform a simple evaluation of the impact of catchment urbanization on the river stage.