Flash floods represent one of the most destructive natural hazards in arid and semi-arid regions, leading to severe infrastructure damage, economic losses, and environmental degradation. This study assesses flash flood susceptibility and mitigation in Wadi Ked, South Sinai, Egypt, using an integrated framework combining Geographic Information Systems (GIS), Multi-Criteria Decision-Making (MCDM), and the Analytical Hierarchy Process (AHP). Eleven conditioning factors were analyzed, including elevation, slope, rainfall, drainage density, land use, soil type, topographic wetness index, curvature, and distances to streams and roads. Results show that the runoff volume of Wadi Ked for a return period of 100 years, 68.14% of the area falls within moderate to very high susceptibility, while 31.86% is classified as low susceptibility. Model validation revealed strong agreement (90%) between literature- and expert-derived weights, with a Kappa coefficient of 0.86, confirming model reliability. Sensitivity analysis demonstrated robustness of the weighting scheme. Hydrological simulation recommended two main storage dams with capacities of 31.72 Mm³ and 12.96 Mm³, reducing peak discharge from 1767.9 m³/s to 33.7 m³/s. A retention basin of 0.74 Mm³ was also proposed for temporary storage, groundwater recharge, and controlled release. Post-mitigation mapping reduction in hazard, with 77% classified as very low susceptibility, 22.53% as low, 0.47% as moderate, highlighting the effectiveness of measures. Although geomorphological constraints limit upstream check dam implementation, distributed mitigation can further reduce runoff impacts. Overall, the study provides a reliable, data-driven framework for flood susceptibility mapping and mitigation planning in arid environments for decision-making.

Arid and semi-arid regions are increasingly suffering from water resource shortage. water stress continues to grow as resulting from increasing populations, urbanization, and global warming. Egypt`s water resources are under increasing pressure. This could soon lead to a severe water crisis if these finite resources are not managed in a sustainable matter. water harvesting could be a solution to solve the problem within potential parts as in Sinai Flash flood is considered as freshwater resources beside its hazards effect in Sinai. floodwater harvesting is seen as a solution to provide another conventional water resource and at the same time mitigate flash flood risk In this study, a methodology for selecting water harvesting sites and techniques was developed for wadi Tayyibah, Abou Zenima, south Sinai, Egypt. The potential runoff was estimated using rainfall -runoff model called HEC-1 based on the SCS-CN method in estimation the runoff. Moreover, ARC-GIS software was used in watershed delineation and produce the required maps for this study The study indicated the location of the dams which can be used to harvest the water and mitigate the hazards of flash floods based on the analysis of data as rainfall data, slop, highways network, geological data, Morphometric properties, and the soil infiltration rate