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.
