Application HEC-HMS to Predict Hydrograph (Case Study in Lebak Petal Sub Basin)

Abstract

A hydrograph is a graph showing changes in the discharge of a river over a period of time. The main factors that influence hydrograph are imperviousness and curve number. Imperviousness is a very useful indicator which to measure the impact of land development on aquatic systems. The value of imperviousness is defined as the sum of roads, parking lots, sidewalks, rooftops, and other impermeable surfaces of the urban landscapes. The curve number is used to determine the amount of precipitation excess that results from a rainfall event over the basin. The purpose of this study is to predict unit hydrograph due to imperviousness and curve number changes. Based on the result, increasing impervious areas lead to reduce infiltration and thereby increased surface runoff within catchments. It makes an effort to volume and peak discharge. From these values make an effort to time of peak discharge. The bigger value of imperviousness and curve number make time of peak early. The bigger value of imperviousness and curve number, make bigger value of peak discharge and volume. It means that imperviousness correlates highly with changes in hydrological indicators time to peak, peak discharge and volume. The outlet value indicates the amount of water flowing to the main channel. The bigger value of imperviousness and curve number make the bigger value of discharge.