EVALUATION OF FLOOD MITIGATION PLAN FOR CIBALIGO RIVER, CIMAHI CITY, WEST JAVA PROVINCE
Keywords:Cibaligo, Flood, HEC-RAS, Normalization, Retention pond
Cibaligo river is one of the major rivers that flow in Cimahi city. During the rainy season, the river is often causing a flood, especially in Melong sub-districts. Several mitigation alternatives have been prepared by the Government of Cimahi City, such as normalization of the river, and construct retention pond. This research is aimed to simulate the mitigation plan hydraulically to examine the effectiveness of the plan alternative. The simulation was done using HEC-RAS software for existing conditions and the condition with mitigation alternatives. The input for simulation collected from 3 nearest climatological stations, whereas SRTM, SPOT 6, and Cimahi City land used map used as a physical condition data input of catchment. A topographical survey was done to measure both cross and long sections of the river and used as simulation input of existing conditions. Two dimensional HEC-RAS simulation applied for each mitigation alternatives such as river normalization, construction of detention pond, and combination of both river normalization and retention pond. The simulation shows that the construction of 125 000 m3 retention ponds has a minimal effect. The combination of both river normalization and construction of ±315.000 m3 retention pond can prevent the area from inundation only for 2 years rainfall period; therefore, other mitigation plans have to be prepared to prevent the area from the flood.