RELIABILITY OF 2D HYDRODYNAMIC MODEL ON FLOOD INUNDATION ANALYSIS

Abstract

This paper presents a flood inundation analysis to determine the possibility of flooding in urban areas. Many studies have conducted flood simulations to generate inundation problems due to river overflow. Urban flood problems commonly occur because of rainfall in subcatchments that do not enter the channel effectively. Therefore, it is necessary to analyze the inundation that occurs owing to overland flow. This study investigates the usefulness of rain-on-grid boundary conditions compared to flow hydrographs to represent the overland flow. The 2D shallow water equation was applied using the HEC RAS 2D model to select suitable boundary conditions to describe watershed problems. The rain-on-grid boundary condition gives a direct rainfall–runoff calculation in the simulation. The flow hydrograph was calculated separately using the rainfallrunoff analysis based on the storm-water-management model. Although rain-on-grid represents the real physical condition, it is difficult for the 2D hydrodynamic model to assess the drainage channel. However, the flow hydrograph boundary condition shows good results compared qualitatively with historical data based on on-site observations obtained from the Department of Public Works, Highways, and Drainage Management. Furthermore, this research provides the capability of flow hydrographs and rain-on-grid boundary conditions for flood simulation in urban areas. The results can be used to conduct an appropriate future simulation of urban drainage planning