Spatial Assessment of Flood Susceptibility Using Remote Sensing and AHP-Based Multi-Criteria Analysis: A Case Study of the Mekerra Wadi Watershed (Algeria)

Floods are among the most destructive natural hazards worldwide, causing significant environmental degradation, economic losses, and social disruption. This study aims to delineate flood-susceptible zones within the Mekerra Wadi Watershed in northwestern Algeria by applying an integrated approach combining remote sensing techniques, Geographic Information Systems (GIS), and the Analytical Hierarchy Process (AHP), a widely used multi-criteria decision analysis method. Ten conditioning factors influencing flood occurrence were considered, including elevation, slope, precipitation, Topographic Wetness Index (TWI), Normalized Difference Vegetation Index (NDVI), drainage density, distance from streams, Stream Power Index (SPI), soil type, and Land Use/Land Cover (LULC). The AHP method was employed to determine the relative importance of each factor, and the resulting weights were integrated through GIS-based weighted overlay analysis to generate a spatial flood susceptibility map. The findings classified the basin into five susceptibility categories, ranging from very low to very high flood susceptibility. The highest susceptibility areas were mainly associated with low-lying terrain, gentle slopes, high drainage accumulation, and proximity to river networks, whereas elevated regions with steeper slopes exhibited lower flood susceptibility. Model performance assessment using the Receiver Operating Characteristic (ROC) curve yielded an Area Under the Curve (AUC) value of 0.915, indicating a high predictive capability. Furthermore, the reliability of the model was confirmed through validation using historical flood events recorded between 2017 and 2019 and in 2022, showing a strong spatial correspondence between predicted susceptibility zones and observed flood occurrences. The resulting flood susceptibility map provides an effective decision-support tool for flood hazard assessment, sustainable land-use planning, and the development of targeted disaster risk reduction strategies in the Mekerra Wadi Watershed.