Efficiency of Geomorphologic Instantaneous Unit Hydrograph (GIUH), Comparing to other Models in Mereg Catchment, Kermanshah.

The Relationship between parameters of Geomorphology and hydrology, provides the possibility to watersheds that there are similarities in terms of geomorphology, by creating relationship between these Parameters, attempting to predict floods in watersheds that have data and its generalization to no data watersheds was similar to each other based on geomorphic parameters. In this context, several methods have been proposed. The aim of this study is to investigate the efficiency of geomorphologic instantaneous unit hydrograph (GIUH) in the preparation of flood hydrograph and compare its performance with Snyder, SCS and Triangular unit hydrograph models, in the Mereg catchment, Kermanshah.  In order to implement these methods, information relating to 12 rainfall –runoff events were collected and the direct hydrograph was obtained. According to statistical indices, Mean Relative Error (MRE), Root Mean Square Error (RMSE), coefficient of bias and Nash Sutcliffe, compare observed and predicted hydrograph showed that the most efficient model in estimating peak discharge is GIUH method and after it Snyder, SCS and triangle methods have the next, respectively. According to the results, Snyder, GIUH, SCS and Triangular methods are respectively estimated as highest performance at the time to peak. Moreover, the results indicate overestimation of GIUH, SCS and triangular methods in estimating peak flows and overestimated and underestimated of Snyder and GIUH methods in estimating of the time to peak. The SCS method also has the best flood volume estimation.