Exploring Flood Susceptibility Mapping Using ArcGIS Techniques Integrated with Analytical Hierarchy Process under Multi-Criteria Decision Analysis in Kanakarayan Aru River Basin, Sri Lanka

Floods are one of the natural disasters causing economic, social, and environmental damage around the world, including in Sri Lanka. Flood susceptibility mapping is essential for flood prevention and mitigation measures. This study aimed to develop and validate a flood susceptibility map for the Kanakarayan Aru River Basin in Sri Lanka. Primary data were collected from water professionals and experts from Provincial Irrigation-Northern Province, Provincial Irrigation-Eastern Province, Disaster Management Centre, and Irrigation Department to decide the significance of flood causative factors. Secondary data of rainfall, digital elevation model, and GIS-based thematic data layers were collected from different agencies. GIS-based spatial multi-criteria decision analysis and analytical hierarchy process method were used for the study. A total of eight flood causative factors, i.e., elevation, slope, precipitation, land use and land cover, river proximity, drainage network density, topographic wetness index, and soil types were identified. Results show that the three mostrelevant factors of flood risk were precipitation (33%), drainage density network (17%), and surface slope (11%). The very high, high, and moderate flood risks occupy 12.5%, 23.4%, and 27.1% of the river basin areas, respectively. The validation process is executed based on the map's comparison of the historical flood locations of the different flood-susceptible zones and it provides a significant accuracy.