Quantification of Citarum watershed damage for flood control efficiency

Abstract

Watersheds damage causes disturbance to the river system and floods. Watershed performance can be monitored regularly through parameters to avoid damage. The purpose of this study is to formulate a quantification of watershed damage based on the flood parameters. This research was conducted in the Citarum River Basin located in West Java Province, Indonesia. The method used is an analysis of the rainfall-runoff model on four Citarum tributaries, namely Citarik, Cisangkuy, Cilember, and Cimahi River. The unit hydrograph resulting from modeling is derived to load discharge using the convolution method. Effective rainfall is determined based on runoff coefficients derived from land-use maps. The discharge capacity of the river is determined by measuring the cross-section of the river near the branching location. Indicator of watershed damage is the ratio between load discharge (Qload) and river capacity discharge (Qcap). The watershed is categorized as damaged if Qload/Qcap > 1. The level of watershed damage is measured by the damage index ID = ?Q/Qcap. Damage categories are low, moderate, and severe. Based on the results of the study, Cimahi river area is not damaged. Citarik River and Cisangkuy River are categorized as low damaged and Cilember River is heavily damaged.