Rainfall Threshold of Citarum River Flood for Early Warning on Urban Area

Floods in Bandung basin located in the upper Citarum river resulted in huge losses because they occurred in industrial areas and densely populated settlements. Disaster risk reduction can be done with flood early warning in residential areas. The purpose of this study is to determine the rainfall threshold that causes inundation in residential areas in seven districts located on the floodplain of the Citarum river. The method used is the analysis of the rainfall-runoff model to obtain the Citarum river unit hydrograph. Flows in the rivers are assumed to be one-dimensional unsteady flow whereas overflow is assumed to be overland flow. Threshold rainfall is determined based on the deconvolution method, with the drainage coefficient calculated based on the land use map. The results of the study are the capacity discharge and the load discharge of the Citarum river in the seven sub-districts, which the most upstream is the Majalaya sub-district and the downstream is Katapang sub-district. The lowest threshold rainfall has occurred in the sub-district Bojongsoang that is 54.34 mm that produced the flood water level as high as 662 m MSL. and the evacuation time for early warning is 5.5 hours.