Integrating GIS and the Information Value Method for Flood Susceptibility Mapping in Dhaka Division, Bangladesh

Flood risk is a function of the flood hazard, exposed values, and vulnerability. Floods are unavoidable events, a high concentration of precipitation on a specific spatial domain that comes with a short warning time, which makes them hard to predict or monitor. Thus, addressing flood issues based on the objective quantification of flood possibilities is important for flood-prone nations like Bangladesh. This paper presents a GIS-based flood susceptibility analysis using the Information Value Method. Eleven causative factors, viz., elevation, slope, aspect, land use and land cover, soil type, distance from river, distance from road, topographic wetness index, drainage density, stream order and annual rainfall, along with previous flood hazard map used for flood susceptibility mapping of Dhaka Division, Bangladesh. Initially, all the required data have been gathered; then, the thematic layers representing all the causative factors for flooding were overlaid using GIS. For each factor, the total flood information value was calculated by summing the individual sub-categories. In conclusion, the final flood susceptibility index for the Dhaka Division, categorized into five levels of very low, low, moderate, high, and very high, accurately reflected the spatial distribution of flood-prone areas. Flood occurrences were predominantly observed in the moderate, high, and very high susceptibility zones, with no significant events recorded in the very low or low zones. This outcome highlights the reliability of the index in identifying flood-prone regions, offering valuable insights for disaster management.