Cartographie de la susceptibilité d’inondation, basée sur l’Analyse Hiérarchique des Procédés (AHP) dans les départements de Pikine et de Keur Massar, Sénégal
Rapid and unplanned urban expansion in low-lying zones of Pikine and Keur Massar has significantly increased flood susceptibility and exposure. In response, flood susceptibility mapping is a strategic tool for urban planning and risk reduction. This study aims to produce a flood susceptibility map for the departments of Pikine and Keur Massar in Senegal, by combining Analytical Hierarchy Process (AHP) with Geographic Information Systems (GIS). Six triggering factors were integrated: rainfall, elevation, slope, drainage density, soil type, and land use. Weighting of the criteria was based on the Saaty method, and the final map was generated through weighted overlay analysis. Landsat-8 and SRTM satellite data, processed via Google Earth Engine, were used to map flooded areas over the period 2015–2024, divided into three sub-periods. The Modified Normalized Difference Water Index (MNDWI) was used to detect flood, while the NDVI helped reduce false detections due to vegetation. The flood frequency map served to validate the AHP-based susceptibility results.
Findings show that 56.60% of the study area’s surface exhibits high and very high susceptibility. By overlaying this data with infrastructure layers, the study reveals that 67.46% of buildings and more than half of the road and railway networks are highly flood-prone. This exposure is largely due to unplanned urban expansion into former water retention basins. The results underscore the urgent need for integrated and resilient spatial planning strategies to mitigate the growing flood risks in these densely urbanized areas. The approach provides a replicable framework for flood risk assessment and infrastructure vulnerability analysis in similar contexts.