TWO ALERT FLOOD EARLY WARNING SYSTEM METHOD BASED ON RAINFALL RUNOFF MODEL

Some residential areas and the main road of Cimahi city that connect Cimahi with other city are often flooded. Based on rainfall runoff model, this research have prepared two alert flood early warning system method with the threshold of river water level and total rainfall. These two alerts indicate that the system is supported by complete flood process and meanwhile rainfall alert still works even though the water level sensor in trouble by sedimentation. Cimahi river cross section in the upstream, midstream and downstream have maximum discharge and water level respectively 730.3 m3 / s and 2.28 m, 95.2 m3 / s and 1.8 m, 59.4 m3 / s and 2.53 m. Cimahi River unit hydrograph generated threshold of total rainfall and time to peak in the upstream, midstream and downstream respectively, 915 mm and 2 hours, 80 mm and 3 hours, 50 mm and 3 hours with 0.57 runoff coefficient. Based on this calculation, the threshold used is the smallest threshold that is in the downstream area and applied as a benchmarking parameter in the upstream. The water level threshold in the upstream is 1.48 m and total rainfall threshold is 50 mm with the time for warning preparation is 3 hours. Bed river elevation is a part of threshold for sedimentation control, that repectively in the upstream, midstream and downstream are 1481.39 m msl, 755.68 m msl and 677.55 m msl. The two alert flood early warning system method as the result of the research is completed with The Information Map of Total Rainfall Threshold and Unit Hydrograph for Cimahi Flood Early Warning System and publish in the public area.