The Wadi Khulab quadrangle, bounded by lat 16°30’ and 17°00’ N. and long 42°00’ and 43°30’ E., is one of the southernmost quadrangle of the Kingdom of Saudi Arabia. It is named after Wadi Khulab, which flows westward across the central part of the area. Approximately one-third of the quadrangle, comprising the mapped area, lies within Saudi Arabia; the remainder lies within the Yemen Arab Republic. Delineation of the international boundary should not be considered definitive.
From west to east, the physiography of the mapped area consists of a portion of the Tiharmat Asir, or coastal plain, extending from the Jizan quadrangle to the west (Blank and Gettings, 1984), a northwest-trending hill range close to the western border of the quadrangle; a pediplain; and the foothills of the Red Sea escarpment. The top of the escarpment is about 50 km east of the mapped area, in the Yemen Arab Republic. Within Saudi Arabia, the highest elevation in the quadrangle about 77 m above sea level, is found at Tirf in the western range of hills.