Risk assessment and zonation of flash flood in Sylhet basin, Northeast Bangladesh using GIS-MCDM tool

Flash flood is devastating natural event that has potential to bring destruction to both infrastructure and civilization. Global warming increases in human-induced land-use patterns exert extra pressure on river channels, resulting in change in river morphology that intensify the frequency and severity of flooding situations. The Sylhet basin in the northeastern part of Bangladesh has considered as one of the most vulnerable zones in the country for flash flood hazards. However, no prior study has been carried out to identify flash flood zone in of this basin, and its mapping for risk zonation being vital steps for inhabitants and decision-makers to minimize and regulate hazard. Present study has carried out using the Remote Sensing (RS) and Geographic Information System (GIS) with Multi-criteria Decision-Making (MCDM) tool and analytical hierarchy process (AHP) to detect and map flash flood risk areas in the basin. The data and information of rainfall, drainage density, geomorphology, flow accumulation, slope, topographic wetness index (TWI), and land use and land cover (LULC) changes are processed using the ArcGIS overlay tool to map flash flood risk and vulnerability zones. Then, the flash flooding risk map is categorized with percentages as high to very high risk (33%), moderate (55%), and low risk (12%). This attempt would aid to local authorities and policymakers in disaster risk response, reduction, and building of flood shelters. Furthermore, it will help to introduce regular and sustainable flash flood prediction, early warning, and management strategies.