Application of Multi-Criteria Decision Analysis Technique for Flood Susceptibility Mapping in an Urban Watershed of Bagmati Basin, Nepal

Abstract

Bagmati Basin within Kathmandu Valley possess the challenge of reoccurring floods mainly in the urban and peri-urban areas. Hanumante watershed, a northeastern tributary of the Bagmati basin in the Kathmandu Valley, is a typical case for urban/peri-urban flooding. Significant recent flood events in the Hanumante Watershed occurred in 2015, 2018, and 2023. Flood assessments in Nepal have traditionally relied on hydraulic models combined with statistical extrapolation of flood discharge. Whereas, this research evaluates the use and utilization of Multi-Criteria Decision Analysis (MCDA) for GIS-based flood mapping. The framework of this study is both innovative and robust, utilizing a unique two-tier MCDA process, with results validated against two different sets of ground-level data. Flood hazard susceptibility was mapped using the Analytical Hierarchy Process (AHP) method, considering 15 parameters categorized under 4 (four) criteria namely Hydrometeorological, Morphological, Soil-permeability, and Land use-land cover (LULC) dynamics. The flood susceptibility map, was validated with the 1-D analysis of Hydrologic Engineering Centre’s River Analysis System (HECRAS) model, a flood benchmarking survey data of the area, achieving an Area Under the Receiver Operating Curve (AUC) >90. Furthermore, the map was verified with georeferenced ground level photographs of Hanumante Flood 2023, demonstrating the accuracy and applicability of the proposed framework of this elaborated study.