Assessment of coastal flood risks in a selected urban area in Bangladesh

The coastal Patuakhali district in Bangladesh is highly susceptible to catastrophic flooding due to its geophysical location. Saving the coastal settlements from these frequent and extreme flooding events is challenging. Thus, there is an urgent need for a detailed flood vulnerability, risk, and capacity assessment study in this area. This study attempted to provide a comprehensive assessment and mapping of coastal flood risk, identifying the most flood-vulnerable regions of the Patuakhali district to achieve efficient flood mitigation strategies. To generate a complete coastal flood risk scenario, this study simultaneously applied people’s perception-based risk assessment using the MCDA, AHP, GIS, and RS-based advanced methodologies. Based on the combined judgments of both people’s perceptions and experiences, GIS- and RS-based mapping, this study predicted a high flood risk for the studied area. Firstly, from people’s perception and expert opinions-based approach, this study estimated a high flood risk (0.886) for the coastal Patuakhali district. Secondly, individual hazard scores of 0.765 and vulnerability scores of 0.644 were obtained during this assessment, which seems reasonable. However, their combined results produced a significant flood risk due to the lower community capacity (0.556) to withstand flood damage. Finally, a flood risk map was developed with the weighted overlay tool, considering ten flood-causing factors throughout the mapping process. Findings showed the majority of Patuakhali district’s central, north-central, most southern, and south-eastern char and island area as being in a very high flood risk zone due to its high population density, development of in-built infrastructure, lower elevation, flat topography, and lack of vegetation cover. This information is supposed to support the relevant authorities and decision-makers.