Integrated Flood Risk Assessment for an Urban Growth Center near Dhaka, Bangladesh

Cities face significant flooding risks due to dense populations and valuable assets, making comprehensive flood risk assessment crucial for effective management. This study evaluates flooding risk in a potential urban growth area of Dhaka City, Bangladesh, employing an integrated approach. Flood hazards were assessed using a one-dimensional hydraulic model, while vulnerability was evaluated through the analytical hierarchy process (AHP), a multicriteria decision-making method. Different probability distribution functions (PDFs) were applied for flood frequency analysis based on discharge and water level, with the Log-Pearson Type-III PDF identified as the best fit. This PDF was used to estimate discharge and water levels for 200- and 500-year return periods. Simulations were conducted using the Hydrologic Engineering Center’s River Analysis System model, calibrated with Manning’s roughness coefficient. Results indicated that approximately 57% and 65% of the study area would be inundated during 200- and 500-year floods, with maximum depths of 8.6 and 9.45 m, respectively. Vulnerability was assessed using factors such as population density, land use, and proximity to key infrastructure, resulting in a classified vulnerability index map by the AHP method. Integration of hazard and vulnerability maps revealed that 40% of the area faces lower flood risk, while 60% has medium to very high risk, aiding urban planners and policymakers in selecting effective flood mitigation strategies.