Island-Scale Vulnerability Assessment of the Sundarbans Using an Ensemble Fuzzy MCDM Framework

Abstract The Sundarbans Delta, the world’s largest mangrove ecosystem, is increasingly exposed to hydroclimatic hazards including sea-level rise, cyclones, storm surges, and salinity intrusion. This study develops an island-scale vulnerability assessment framework that integrates four multicriteria decision-making (MCDM) techniques, i.e., analytic hierarchy process, analytic network process, multiexpert ranking evaluation criteria, and ordinal priority approach, within a trapezoidal fuzzy logic scheme. Twelve criteria grouped into manpower, infrastructure, economic, and environmental loss were evaluated for four representative Indian Sundarban islands: Gosaba; Namkhana; Kultali; and Sagar. Ensemble weights indicate that cyclones and storm surges are the dominant drivers (normalized weight ≈ 0.28–0.32), followed by habitat destruction and waterlogging, whereas pollution and loss of upstream connectivity contribute more modestly. The ensemble scores classify Gosaba as excessive high vulnerability (fuzzy range 0.8–0.9), with Namkhana, Kultali, and Sagar in the very high and high categories, respectively. The results provide an operational ranking of islands for prioritizing embankment strengthening, cyclone-shelter siting, and mangrove restoration. The proposed ensemble fuzzy MCDM framework reduces subjectivity compared with single-method indices and is transferable to other small-island and deltaic systems requiring transparent, reproducible vulnerability metrics for hydrologic and coastal engineering decisions.