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Abstract

A great number of developing countries do not have sufficient rainfall-rainoff data of watersheds. For designing a hydraullic structure, considering the basic characteristics of synthetic unit hydrograph is quite indispensable. The geomorphoclimatic approach considers the rainfall and the properties of the watershed. This method can provide a better representation of the runoff estimation. In this study, a geomorphoclimatic instantaneous unit hydrograph (GcIUH) model has been developed. It’s derived from the parameters of the CLARK instantaneous unit hydrograph(IUH) which completes its shape. GcIUH based Clark model was applied from the Kasilian watershed in northern part of Iran. The Direct Surface Run Off (DSRO) hydrographs are estimated by the GcIUH based Clark model. Its DSRO hydrographs have been compared with the DSRO hydrographs computed by the Clark IUH model option of the HEC-HMS package. On the basis of quantitative evaluation of the model, it was found that the model is applicable for predicting storm surface runoff in the study area.

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