GIS and DEM Based Watershed Characteristics of Wadi Al-Adaira Basin, KSA

The study aimed to evaluate the possibility of using the digital elevation model (DEM) technique based on GIS in the automatic extraction of the drainage basin network and calculating its parameters. The study used the digital elevation model from ASTER DEM (30 m) data for Wadi Al-Adaira basin and its sub-basins using Arc GIS 10.5 and its extensions: spatial analyst tools, 3D analyst tools and ArcHydro and then computed the morphometric parameters for the drainage of sub basins. Morphometric parameters for drainage basins include: Area (ranged between 92.5 km² and 3323.06 km²), Max. Length (ranged between 17.06 km and 152.93 km), average width (ranged between 4.51 km and 21.73 km), perimeter (ranged between 62.45 km and 610.03 km), elongation ratio (ranged between 0.43 and 0.77), circulation ratio (ranged between 0.11 and 0.32), and form factor (ranged between 0.14 and 0.46). Morphometric parameters of drainage networks include: Stream order (ranged between 4 and 5), Stream number (ranged between 44 and 1448), Stream lengths (ranged between 93.74 km and 3383.04 km), bifurcation ratio (ranged between 0.71 and 0.83), drainage density (ranged between 0.86km/km² and 1.13 km/km²), Stream frequency (ranged between 0.40 strm/km and 0.50 strm/km) and drainage texture (ranged between 0.52 strm/km and 2.37 strm/km). Drainage basin relief parameters include: relief (ranged between 58m and 815m), mean slope (ranged between 2.55 deg. and 10.19 deg), slope aspect, relief ratio (ranged between 0.002 and 0.028), relative relief (ranged between 0.001 and 0.009), ruggedness number (ranged between 0.05 and 0.829), geometric number (ranged between 19.28 and 155.64) and Hypsometric integral (ranged between 0.17 and 4.08). The study concluded that the use of a digital elevation model based on GIS from ASTER DEM data is a more effective and successful method in the automatic extraction of morphometric parameters for drainage basins, integrated with topographic maps and satellite images.