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

Abstract

Flash oods 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 ash oods and manage the available water resources from the infrequent and rare rainfall storms. The goal of this study is to create a potential ood hazard map and a map of suitable locations for RWH in Wadi Nisah, Saudi Arabia for future water management and ood prevention plans and to identify potential areas for rainwater harvesting and dam construction for both a ood 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 ood hazard mapping criteria were elevation, drainage density, slope, direct runoff depth at 50 years return period, Topographic witness index, and Curve Number, according to the Multi-criteria decision analysis, while the criteria for RWH were Slope, Land cover, Stream order, Lineaments density, and Average of annual max-24hr Rainfall. The weight of each criteria was estimated based on Analytical Hierarchy Process (AHP). In multi-criteria decision analysis, 21.55 % of the total area for Wadi Nisah was classi ed as extremely dangerous and dangerous; 65.29 % of the total area was classi ed as moderate; and 13.15 % of the total area was classi ed as safe and very safe in ash ood 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. According to the developed RWH potentiality map, two possible dam sites were proposed. The maximum height of the proposed dams, which corresponded to the cross section of dam locations, ranged from 6.2 to 9 meters; the maximum width of dams ranged from 573.48 to 725 meters; the maximum storage capacity of reservoirs, which corresponded to the distribution of topographic conditions in the surrounding area, ranged from 3976104.499 m 3 to 4328509.123 m 3 ; and the maximum surface area of reservoirs ranged from 1268372.625 m 2 to 1505825.676.14 m 2 . These results are highly important for the decision makers for not only ash ood mitigation but also water management in the study area.Highlights 1. The potentiality of using RS data and GIS tools together with and Multi-Criteria Decision-Making tools (MCDM) to assess the ood hazard.2. In ash ood hazard classes, 21.55 percent of the entire area for Wadi Nisah was categorized as highly hazardous and dangerous; 65.29 percent of the total area was rated as moderate; and 13.15 percent of the total area was classi ed as safe and very safe.3. Two prospective dam locations were presented based on the generated RWH potentiality map.