Risk assessment and management of vulnerable areas to flash flood hazards in arid regions using remote sensing and GIS-based knowledge-driven techniques

Earth Observation from space has allowed characterizing, detecting, and managing natural hazards in spatiotemporal scale. Flash flood is the most frequent natural disaster that causes destruction to human lives, the economy, and infrastructure. Thus, developing a flash flood hazard zone (FFHZ) map is significant for comprehensive flash flood risk assessment and management to minimize its harmful effects, particularly in residential areas, because of climate change. Therefore, in this article, ten parameters derived from satellite images, including lithology, slope, topographic wetness index (TWI), Stream Power Index (SPI), Stream Transport Index (STI), Terrain Roughness Index (TRI), drainage density (Dd), distance to river, radar intensity map, and rainfall distribution map, were fused to predict the flood-vulnerable areas through GIS-based overlay analysis after normalization and assigning weight by applying Analytical Hierarchy Analysis (AHP). The findings allowed for the identification of the most vulnerable areas and provided an explanation for the flood's effects on New Qena City (NQC). The output FFHZs of the Wadi Qena Basin (WQB) were divided into six hazard zones, i.e., extreme hazard (6.86%), very strong (15.04%), strong (18.74%), moderate (22.58%), low (22.80%), and very low (13.98%) susceptibility. Furthermore, approximately 35% of the under-construction NQC is subject to the extreme to very serious hazards, as opposed to the extension area to NQC east of the Qena-Safaga Road. Interferometry Synthetic Aperture Radar (InSAR) change detection coherence (CCD) and spatiotemporal analysis of Landsat and Sentinel-2 data revealed steady changes in vegetation and infrastructure from 1984 to present. Based on GIS analyses about 10, and 14% of the NQC can be inundated if the flood extends 500, and 1000 m around the flood canal, respectively. Thus, several strategies were advised to safeguard the development projects, particularly the residential sections of the under construction NQC, including erecting four dams with a total capacity of 300 million m 3 , reinforce the dam at Wadi Shahadein , constructing concrete chevron bunds along the flood zone, and extending the depths of the flooding canal.