Geospatial flood susceptibility modelling using analytical hierarchy process: A case study in the south-central coastal region of Bangladesh

The Patuakhali region is situated in the coastal area of Bangladesh and is bordered by major rivers, which are extremely vulnerable to foreseeable flooding disasters due to the detrimental effects of climate change. The primary objective of this study is to create a flood susceptibility map using AHP, GIS, and Remote Sensing techniques. The flood hazard map was constructed using seven important causative factors, where elevation (32 %) is the most influential in creating flood hazards, followed by slope (22 %) and drainage density (14 %). The flood hazard map shows that 10.30 % area is very highly hazardous, 22.20 % is in high, 30.45 % is moderate, 26.06 % is low, and 10.99 % area is in very low hazard zone in the study area. The flood vulnerability map was developed using four key factors: population density, distance from roads, land use/land cover (LULC), and NDVI, with population density emerging as the most influential factor, contributing 45 % to the overall vulnerability assessment. The map indicates that 30 % of the area is classified as very high, 23 % as high, 22 % as moderate, 17 % as low, and 9 % as very low vulnerability. Likewise, the flood hazard and vulnerability maps were overlaid to construct a flood risk map. In the final AHP-GIS flood risk map, 10 % of regions were classified as very high risk, 22 % as high risk, 28 % as moderate risk, 24 % as low risk, and 16 % as very low risk. The information contained in these maps will be beneficial to decision-makers in implementing flood-mitigation policies in priority areas of sustainable development, as well as in preventing and managing floods in the coastal belt of Bangladesh. Further analysis, which includes data on population and building density, proximity to nature, and economic and social activities, will enable the enhancement of sustainability in addition to this study.