GIS-Based Flood Susceptibility Mapping Using AHP-MCDA: A Case Study of Sherpur District, Bangladesh

Flooding is one of the most destructive natural disasters, causing significant loss of life and damage to property worldwide. In the context of global warming and climate change, both the frequency and intensity of floods have increased, resulting in more severe impacts. The Sherpur District of northern Bangladesh is highly susceptible to transboundary flash floods triggered by intense monsoon rainfall in the upstream Garo Hills of India. The floodplain areas of this district experience flooding at least once every year. Therefore, flood hazard zonation mapping is essential for effective disaster risk management and mitigation. This study aims to identify flood-susceptible zones in Sherpur District using a Multi-Criteria Decision Analysis (MCDA) approach. Several physical indicators, including rainfall, Topographic Wetness Index (TWI), Land Use/Land Cover (LULC), drainage density, slope, elevation, and proximity to rivers and roads, were considered to assess flood susceptibility. These factors were analyzed in a Geographic Information System (GIS) environment, and their relative importance was determined using the Analytical Hierarchy Process (AHP). The resulting flood hazard map was classified into four susceptibility zones: very high, high, moderate, and low. Approximately 28% of the district falls within the high to very high hazard zone. The reliability of the flood hazard map was evaluated using the Receiver Operating Characteristic (ROC) curve and Area Under the Curve (AUC) methods based on historical flood inundation data. The model achieved an AUC of 0.87. The results indicate that the low-lying upazilas of Nalitabari, Jhinaigati, and parts of Sherpur Sadar, particularly those adjacent to the flashy Bhogai and Chellakhali river systems, fall within the high to very high flood hazard zones due to their low elevation, gentle slopes, and high drainage density. The hazard map provides a decision-support tool for policymakers, planners, and disaster management authorities in implementing effective flood mitigation strategies, emergency response planning, and sustainable land-use management.