Nash IUH parameters estimation using method of moments - A case study

Abstract

Flood forecasting plays an important role in mitigating the natural disaster. Among the available methods for flood forecasting, the unit

hydrograph (UH), and instantaneous unit hydrograph (IUH), is widely and successfully used. In case of IUH it is assumed that the

hydrograph generation was affected by number of ‘n’ linear reservoirs having similar/same storage coefficient ‘K’ value. The IUH

proposed by Nash has been widely used in rainfall-runoff (RR) simulation as well as for flood forecasting. However the success of

application of Nash IUH model is based on the accuracy of the estimated parameters ‘n’ and ‘K’ for a given catchment. This study

describes the development and application of Nash IUH for the Koyna watershed in Maharashtra, India. The parameters are estimated

using method of moments (MOM). This IUH may be useful for predicting the flash flood in to the reservoir for a given rainfall. The

obtained direct runoff hydrograph (DRH) estimated from IUH derived is compared with the observed DRH and found to be in good

agreement with each other. The performance of the IUH model has been assessed using coefficient of correlation (R), Root mean square

error (RMSE), error in peak inflow prediction (%MF) and time to peak flow.