Urban Flood Risk Mapping and Mitigation of Bhubaneswar City, India, Using AHP and SWMM with GIS

Urban flooding has become a serious issue in many fast-growing cities, demanding integrated approaches that combine geospatial, hydrological, spatial, and hydraulic modeling perspectives. This research introduces a comprehensive GIS–AHP–SWMM-based method to evaluate urban flood hazards, vulnerabilities, and overall risk within Bhubaneswar Municipal Corporation (BMC), India. A total of 14 indicators were employed—seven describing the physical characteristics influencing flood hazard, such as Topographic Wetness Index, slope, elevation, rainfall intensity, and drainage density; and seven reflecting vulnerability aspects, including population concentration, terrain ruggedness, soil permeability, land use, and accessibility to essential infrastructure, such as hospitals and roads. The Analytic Hierarchy Process (AHP) was applied to determine the relative significance of each factor, ensuring logical consistency (CR < 0.1). Weighted overlay analysis within ArcGIS produced spatial maps of hazard, vulnerability, and flood risk at a 30-m resolution. The Storm Water Management Model (SWMM) was then used to simulate the city’s drainage performance under design-storm scenarios derived from Intensity–Duration–Frequency (IDF) relationships based on Gumbel’s distribution. Model validation against 173 recorded flood events indicated strong performance, with an overall accuracy of 82.4 percent and an AUC value of 0.86. Findings suggest that approximately 39 percent of Bhubaneswar is exposed to high or very high flood risk, particularly across low-lying and densely inhabited areas. Sensitivity testing, with a ±10 percent variation in weightings, confirmed more than 90 percent spatial stability. The proposed GIS–AHP–SWMM framework offers a robust, transferable approach for urban flood risk analysis, supporting sustainable flood management and resilience planning in other rapidly developing cities.