The Estimation of Runoff Volume and Maximum Discharge by Using Curve Number (CN) Method (Case Study in Darrehshahr Drainage Basin)

A valid estimation of runoff volume and maximum discharge in the dried and semiarid regions which lack data is important for flood management. One of the estimating methods of runoff volume is related to curve number (CN) of American soil conservatives services (SCS). In this study, the drainage basin of Darrehshah Sarab has been studied with regard to its runoff volume potentiality, maximum discharge and effective factors. To estimate the runoff volume and maximum discharge of the sub-catchments, the curve number method has been used. First, the layers and the needed data including the land use, soil hydrological groups and a maximum 24 hours precipitation was prepared for basin. Then the CN values, infiltration (S), runoff volume (Q) and maximum discharge (Q max) were calculated for the entire basin and each sub-basin. Finally, factor analyses based on 19 parameters were used to identify the effective factors on maximum discharge at sub-basins. The results showed that among the used parameters in sub basins, two physiographic parameters (area and drainage density) were effective parameters in flooding potential of the drainage basin of Darrehshah Sarab.