Derived flood frequency distribution for negatively correlated rainfall intensity and duration

Derived flood frequency distributions (DFFD) are relatively new in the field of hydrology. These models use rainfall and catchment characteristics for deriving the flood frequency distribution. The DFFD models developed so far use joint probability density function of exponentially distributed rainfall intensity and duration and consider these variables as independent of each other. In reality this may not be true and these variables may be correlated as well. In the present paper a physically based flood frequency model has been developed for negatively correlated rainfall intensity and duration. In the model, infiltration losses are represented by the phi index. The geomorphoclimatic instantaneous unit hydrograph (GcIUH) is used as the effective rainfall-runoff model.