Floods are among the most significant natural hazards threatening communities, driven by climate change and human activities. Al-Ghamqa River Basin, located south of Tartous city, is highly vulnerable to floods and soil erosion due to the absence of soil conservation practices and water storage structures. In this study, an integrated AHP–GIS methodology was applied to classify Al-Ghamqa sub-basins according to flood hazard susceptibility. Using SRTM 30m digital elevation model data, fourteen sub-watersheds were delineated within Al-Ghamqa River Basin, and thirteen key morphometric parameters were calculated, covering linear, areal, and relief aspects. The Analytic Hierarchy Process (AHP) was used to assign weights to these parameters through pairwise comparison matrices. The results indicated that drainage density (Dd) and stream frequency (Fs) were the most influential parameters in flood susceptibility, each with a weight of 0.152. The sub-watersheds were classified into five priority levels: Very High (28.61%), High (16.23%), Moderate (18.15%), Low (14.10%), and Very Low (22.91%). The ROC–AUC analysis produced a value of 0.865, confirming the model’s high predictive accuracy.