Flood Risk Mapping in the Najran Basin, Saudi Arabia Based on aFuzzy AHP–GIS Model

Flooding poses a significant hazard in arid and semi-arid regions, where intense but infrequent rainfall events can result insevere damage to infrastructure, livelihoods, and public safety. This study assesses flood susceptibility in Wadi Najran, SaudiArabia, by integrating the Fuzzy Analytical Hierarchy Process (FAHP) with Geographic Information Systems (GIS). Eight keyflood conditioning factors were selected for analysis based on hydrological significance and regional relevance: elevation, slope,drainage density, rainfall, land use/land cover (LULC), soil type, the Normalised Difference Vegetation Index (NDVI), and theTopographic Wetness Index (TWI). The FAHP method was used to structure expert judgment under uncertainty and assignrelative weights to each factor. The results indicate that drainage density (26.7%), slope (23.0%), and elevation (19.8%) arethe most influential factors contributing to flood susceptibility in the study area. These were followed by rainfall (9.8%), LULC(7.1%), soil type (5.8%), NDVI (4.3%), and TWI (3.5%). A final flood susceptibility map was developed using a weighted overlayapproach and classified into five susceptibility levels: very low, low, moderate, high, and very high. Approximately 48.6% ofthe study area falls under high or very high susceptibility zones, particularly downstream of Najran Dam and along NajranValley. The findings are consistent with previous studies and technical reports and provide a valuable spatial reference for floodrisk mitigation and sustainable urban planning. The FAHP-GIS framework offers a transparent, adaptable, and cost-effectivesolution for flood risk assessment in data-scarce environments.