Integrated Hydrologic Study of the Arid and Semi-arid Regions using RST and GIS in the Riyadh Metropolitan Area, Saudi Arabia

Abstract

Water is extremely critical for human survival. It is therefore important to efficiently manage integrated water resources, which includes basins, watersheds, and wadies. In this study, the freely available data was used, which included a digital elevation model, soil and geological maps, satellite imageries, and daily precipitation records. Furthermore, remote sensing techniques and geographic information system were also integrated in this study. The linear and areal aspects, along with the longitudinal profile were also included, and the hydrologic soil groups (HSGs), land use/land cover (LULC), and curve number (CN) were identified for the main basin of the Riyadh capital. The morphometric analysis indicated that the total area of the main basin was 8500 km2, with 40 watersheds and the highest stream order as eighth. The drainage density of the main basin was 1.57 km/km2. Impermeable surface constituted most of the basin area, as group D was the most prevalently found HSG, constituting 71% of the total basin area. Additionally, the main basin had a highly steep slope, with varying elevations. Furthermore, four types of LULC were identified in the basin namely urban-based, barren land, cultivated land, and ways. The CN for every cell of the main basin ranged from 64 to 98, and the basin weighted CN was found to be 92. The potential direct runoff ranged from 10 to 59 mm. More than 70% of the total area was found to be vulnerable to high and very high runoffs (> 35 mm). These values confirmed the occurrence of flood events, particularly in urban areas and cultivated lands.