Predicting flood hazards area using swat and hec-ras simulation in Bila river, South Sulawesi

Sidrap Regency is one of the special economic zones in South Sulawesi. It has been growing rapidly from rural land to an industrial city since mid-2005. With the process of urbanization, flooding has become a threat to the security of the city area. In this study, Bila River basin in Sidrap Region was selected to investigate the effect of urbanization on surface runoff and peak discharge. The methodology involved hydrology database building, a detailed Digital Elevation Model (DEM), a land use cover and a soil map of the basin. With all these data, the SWAT model (Soil and Water Assessment Tool) was used to predict discharge values. These discharge values were used, along with the DEM, to predict flood hazard areas in the Bila river basin floodplains. This procedure was made using the HEC-RAS model (Hydrological Engineering Centre-River Analysis System). The results of SWAT Model showed that changes in land use had a significant impact on increasing river discharge. The results of HEC-RAS show that with a planned flood of a return period of 10 years (840 m³/s) can cause flooding on Bila River, because the existing capacity for this river is 412.70 m³/s. The study shows the 2D capability of the new HEC-RAS 5 for flood inundation mapping and management studies.