Influence of impervious cover determination method of upper Ciliwung watershed on flood warning system level change in Katulampa weir

Abstract

The Katulampa Weir is a part of Jakarta Flood Early Warning System for the Ciliwung River. The measured water level fluctuation in the Katulampa Weir is affected by the physical condition of the Upper Ciliwung Watershed. In this study, the definition and relevance of the impervious cover determination method based on the Total Impervious Area (TIA) and Effective Impervious Area (EIA) in generating design flood discharge and its effect on the change of flood early warning level in Katulampa Weir will be evaluated. Identification of land use distribution is based on digitized process used combined GIS maps using visual interpretation of high resolution satellite images 2017. The flood analysis for both methods is applied to the same rain conditions. Evaluation of flood early warning level changes are based on flood discharge simulated results and rating curve discharge in the Katulampa Weir. The simulation by WinTR-20 gives that maximum discharge using TIA method is 150 m3/s and EIA method 139.5 m3/s. There is no significant difference between and both are classified as the same level of flood early warning system level, which is on stage 3. However, for large watersheds, it takes much effort to identify and digitize an effective impervious area.