Flood modelling at Bandar Batu Pahat, Johor using HEC-RAS software

Abstract Flood catastrophe continuously hit Malaysia through monsoonal flood and flash flood as well posing threat towards people, infrastructure and environment. Batu Pahat is among the district in Johor affected by flood disaster for almost every year. This study conducted to determine the hydraulic and hydrological characteristic and the ability of drainage system in Parit Besar and Jalan Pontian-Batu Pahat catchment area at Batu Pahat using HEC-RAS software. Through HEC-RAS, floodplain map was also produced to access the overview of potential floodplain areas. Survey data, geometric data and flow data were computed in HEC-RAS to produce drainage flow and cross-sectional area along the catchment area. Four (4) flow rates of 0.05284, 0.05894, 0.06910 and 0.07113 (m 3 /s) were utilized to identify the drainage ability to accommodate additional water. Several stations in Parit Besar catchment cannot accommodate the runoff with the minimum flow rate of 0.05284 (m 3 /s). Meanwhile, Jalan Pontian-Batu Pahat catchment cannot accommodate flow rates of 0.06910 and 0.07113 (m 3 /s). This is due to the catchment area has low elevation and insufficient drainage system. From the results, floodplain areas were identified. Modification of drainage cross-section was proposed to reduce the floodplain areas. This study is vital for better understanding of flooding and help the authorities to produce better flood management plan.