<p>Waterlogging is a critical challenge for urban areas worldwide, particularly in rapidly urbanizing regions with inadequate drainage infrastructure. This study develops a Composite Waterlogging Vulnerability Assessment Index (CWLI) and applies it to the Chattogram City Corporation area of Bangladesh to evaluate spatial vulnerability. Twenty-five potential factors were initially identified from the literature, and following expert consultation, six key factors were selected: surface runoff, aspect, distance from drainage networks, tidal water influence, solid waste management, and surface geology. Surface runoff was estimated using the Soil Conservation Service Curve Number method, while the remaining factors were analyzed through geospatial techniques. The Fuzzy Analytic Hierarchy Process was employed to assign weights to these factors, enabling the formulation of the CWLI. Integrating all factors layers, the CWLI produced a vulnerability map showing 13% of the area is highly vulnerable, 17% moderately high, 30% moderate, 18% low, and 22% very low. These findings pinpoint critical zones requiring urgent intervention while highlighting more resilient zones. The CWLI provides a valuable decision-support tool for policymakers, urban planners, and disaster management authorities to identify high-risk locations, prioritize interventions, and design targeted strategies to mitigate waterlogging impacts. Furthermore, the methodology’s adaptability makes it applicable to other urban contexts in Bangladesh and beyond. Future research could enhance the model by incorporating real-time hydrological data and stakeholder-driven risk assessments.</p> Graphical Abstract <p></p>