A GIS morphometric analysis of hydrological catchments within Makkah Metropolitan area, Saudi Arabia

Spatial information technologies, particularly the Geographical Information Systems (GIS), represent efficient tools in determination of drainage basin morphometric properties for water resources management and environmental planning. GIS and a highresolution Digital Elevation Model (DEM) have been utilized for the morphometric analysis of six basins exist within Makkah metropolitan area, southwest Saudi Arabia. Several morphometric parameters have been computed and analyzed,such as total relief, relative relief, relief ratio, ruggedness number, texture ratio, elongation ratio, circularity ratio, form factor ratio, drainage density, stream frequency, sinuosity factor, and bifurcation ratio. Impacts of morphometric parameters on flash flood characteristics have been also investigated. It has been found that the catchment no. 3 has the least time of concentration, the highest runoff depth. Such hydrological hazards are mainly due to the basin's small area and its highest relief ratio, relative relief, and ruggedness factor. Hence, it is concluded that this specific catchment might be considered as the most hazardous area in Makkah city in terms of flash flood impacts. Therefore, it is recommended that the attained results be utilized in water resources management and environmental planning in Makkah city.