Designating Appropriate Areas for Flood Mitigation and Rainwater Harvesting in Arid Region Using a GIS-based Multi-criteria Decision Analysis

Flash floods are highly devastating, however there is no effective management for their water in Saudi Arabia, therefore, it is crucial to adopt Rainfall Water Harvesting (RWH) techniques to mitigate the flash floods and manage the available water resources. The goal of this study is to create a potential flood hazard map and a map of suitable locations for RWH in Wadi Nisah, Saudi Arabia to identify potential areas for rainwater harvesting and dam construction for both a flood mitigation and water harvesting. This research was carried out using a spatiotemporal distributed model based on multi-criteria decision analysis by combining Geographic Information System (GIS), Remote Sensing (RS), and Multi-Criteria Decision-Making tools (MCDM). The flood hazard mapping criteria were elevation, drainage density, slope, direct runoff depth at 50 years return period, Topographic witness index, and Curve Number, while the criteria for RWH were Slope, Land cover, Stream order, Lineaments density, and Average of annual max-24 h Rainfall. In multi-criteria decision analysis, 21.55% of the total area for Wadi Nisah was classified as extremely dangerous and dangerous; 65.29% of the total area was classified as moderate; and 13.15% of the total area was classified as safe and very safe in flash flood hazard classes. Only 15% of Wadi Nisah has a very high potentiality for RWH and 27.7%, 57.31% of the basin has a moderate and a low or extremely low potentiality of RWH, respectively. ranged from 3976104.499 m to 4328509.123 m; and the maximum surface area of reservoirs ranged from 1268372.63 m to 1505825.676.14 m.