Harnessing satellite precision: flash flood vulnerability mapping in arid wadis

In arid and semi-arid regions, flash floods pose significant threats to human life and infrastructure, especially in the geomorphologically intricate environments of wadis. Effective risk management and mitigation require accurate assessment and analysis of flash flood susceptibility. The instrumental role of remote sensing is evident in accurately delineating land use and land cover (LULC), a foundational layer for flash flood risk assessment. The primary phase of this study is to evaluate the quality of the LULC classification using Sentinel-2 and Landsat-8 satellite imagery. The Gharbia Governorate in Egypt, with its varied land uses including Built Area, Water, Crops, and Agricultural Land, was exploited for this assessment. With the integration of remote sensing, GIS, and MCDM methods, this study aims to enhance the reliability of flood risk evaluations. Morphometric factors such as soil, geology, drainage, slope, LULC, and elevation were assessed, weighted, and integrated using the Analytic Hierarchy Process (AHP) to delineate flash flood risk zones in Wadi El-Assiuty, Egypt. Findings indicate that Sentinel-2 data outperforms Landsat-8 in LULC classification accuracy. The flash flood risk map reveals that most areas in Wadi El-Assiuty exhibit moderate to high inundation risk. The weight results were consistent with previous studies, while the drainage is identified as the most significant factor influencing flood risk (28%), followed by geology (23%) and LULC (16%). Furthermore, the case study risk map reveals that the southwestern region is identified as a high-risk area due to its high drainage capacity, low elevation, extensive urbanization, and geological features like fanglomerate and Pliocene deposits. These insights are valuable for land-use planning and disaster preparedness in arid regions.