Floods have become one of the major disastrous events in Malaysia’s developed and urban areas. Rapid development in the state caused the runoff water to increase from time to time, becoming a challenge in the water management sector. Furthermore, land use change impacts the consequences of worst events as the excessive runoff increases. Since the effects of land use change over time, it is likely to alter the hydrologic regime of the area and gradually decrease the existing infrastructure’s protection level. Furthermore, continued reliance on the performance of existing drainage infrastructure over its service life will be inadequate since future performance will depend upon future rather than past conditions. This study models the rainfall-runoff processes and models the flood inundation for the Selangor River basin. A hydrodynamic model was performed, and multiple scenarios of design rainfall were used to generate the flood hazard extent in the Selangor River basin. The hydrodynamic model comprising hydrological and hydraulic analysis was able to simulate acceptable streamflow outputs and inundation depths.