Assessment and Zonation of Flood Susceptibility in Sylhet Division, Bangladesh Using GIS and Analytic Hierarchy Process (AHP)

Abstract

Flooding poses a persistent challenge in Bangladesh, where complete prevention remains difficult due to its geographical and climatic conditions. This study integrates the Analytical Hierarchy Process (AHP) with Geographic Information System (GIS) techniques to create a detailed flood susceptibility map for the Sylhet division in northern Bangladesh. The primary goal is to classify the region into distinct flood susceptibility zones, providing valuable insights for improving flood risk management, mitigation, and preparedness strategies. The study evaluates 12 critical flood-influencing parameters, including elevation, slope, topographic wetness index (TWI), precipitation, drainage density, proximity to roads and rivers, vegetation, land use and land cover (LULC), and soil type. These factors were chosen based on their established relevance to flood dynamics, with data sourced from reliable spatial databases to ensure accuracy. Using AHP, weights were assigned to each parameter based on expert input, reflecting their relative importance in flood risk. These weighted factors were then integrated using GIS overlay analysis and weighted linear combination techniques to generate a flood susceptibility map. The results show that approximately 35.27% of the Sylhet division, particularly the northern regions and the low-lying Haor basin, fall into the “high” flood susceptibility categories. These areas are highly vulnerable due to their flat topography, proximity to major rivers, and inadequate drainage systems. In contrast, the southern and southwestern areas, accounting for around 7.45% of the region, exhibit “low” flood susceptibility, benefiting from higher elevations and better natural drainage. This flood susceptibility map serves as an essential tool for identifying high-risk areas, supporting targeted flood mitigation efforts, and enhancing disaster preparedness. By providing a scientific foundation for effective flood management, the study aids decision-makers in reducing flood impacts and promoting the sustainable development of flood-prone regions in northern Bangladesh.