Runoff Generation Modeling for Kurdistan Province Watersheds by using Physiographic and Climatic Variables

Flood is among phenomena which result considerable damages to resources and is a serious issue among hydrologists. The proper estimation of runoff is necessary for designating appropriate approaches for its control or optimal management. Various problems have been reported in application of empirical models. The regional analysis of runoff with different return periods by applying watershed characteristics is an alternative with numerous applications. In this study, mean discharge data of 7 hydrometric stations in Kurdistan Province watersheds, Iran, were collected for a period of 30 years and discharges with return periods of 2, 5, 10, 20, 25, 50, 100 and 200 years were consequently calculated using SMADA package. The relationship between mean discharges with different return periods and 26 physiographic and climatic factors were evaluated by using bivariate and multivariate regression models using SPSS 13.5 package and their partial influence were also determined. The results of the study showed that the nonlinear models performed better than linear regression. The main variables include the area, main waterway length and Gravellius factor. Data analysis also revealed the possible change of variables and their importances in determination of monthly mean discharges with different return periods.