7.8-Simulation of flood flows in a mountainous catchment in western ghats (India)

Abstract

Floods in the mountainous areas result from high intensity rains falling over steep slopes and transforming into runoff at outlet very rapidly due to less time of concentration. The rainfall runoff process in the mountainous catchment is a complex phenomenon compared to plain areas. In these areas, precipitation occurs more frequently and some times with high intensities for longer duration resulting in flash floods. For simulation of flood flows in small mountainous catchments, lumped models are convenient to use because of their simplicity. Unit hydrograph technique is one of the simple and widely used technique for simulation of flood flows. In this paper the representative unit hydrograph is derived using Clark model. The computations are performed using one of the options for unit hydrograph derivation based on Clark's unit hydrograph approach available in the HEC-1 Flocd Hydrograph Package. The rainfall runoff data for eight flood events of Hemavati sub-basin up to Sakleshpur (drainage area 600 sq. km.) are used in the study. The Clark's model parameters TC and R were calibrated using four events. The calibrated model is applied to reproduce four flood events in order to validate the model performance. It is observed from the study that the model generally reproduces the flood peak magnitudes, time to peak and overall flood hydrograph reasonably well.