Abstract

This paper revisits the popular rainfall-runoff Soil Conservation Service Curve Number (SCS-CN) methodology in perspective of Strange (1892),1 rainfall-runoff procedure widely used in Southern parts of India. It amends the Hawkins’ (1993) concept of CN decaying with increasing rainfall (P) for complacent watersheds, which contrasts the general notion that the runoff coefficient (C) (or CN, another form of C) increases with increasing P. Its roots lie in the existing potential maximum retention (S)-CN mapping relationship. Besides suggesting a rational modification to this relationship, a more rational form of the SCS-CN methodology is presented and is found to work satisfactorily on the strange data.

Keywords

complacent watershed, curve number, CN-P relationship, NEH-4, rainfall-runoff relation, soil conservation service curve number method, strange table