Relationship between NASH Instantace Unit Hydrograph parameters and Flow physiographical characteristics in some selection watersheds iran

Instantaneous unit hydrograph is one of the methods that could be used for estimation of flood event hydrograph. In ungaged basins، its application needs estimation of storage coefficient (k) and number of reservoirs (n). In this research، in order to investigate relationship between IUH’s parameters and basin characteristics، at first hydrograph and hyetograph of 5-9 flood events from 6 basins with different climate collected and then IUH’s parameters calculated for each event using moment methods. Multiple regression analysis between IUH’s parameters، basin characteristics and some of rainfall and flow characteristics showed that area and excess rainfall and ratio of mean stream length to basin slope are effective in n and k and are significant in 95%. The mentioned relationship is of linear regression and could be applied in other basin with similar characteristics.