The length of the Allan is about . The river flows southward from the foot of
Tell al-Hara, a
volcanic cone representing the highest point in the Hauran plain, through the stony, volcanic cone-covered country where the river has an altitude of approximately above sea level. Here it is slightly lower than the roughly parallel Ruqqad river, which flows west of the Allan. The river's altitude declines to about after it passes near the
tell of Beit Akkar, considered by some scholars to be the site of the
biblical city of
Golan, then drops another down a cliff. The river becomes narrow at this point and is joined by a ravine called the Wadi Beit Akkar. After about , the river again falls about over a cliff. A little beyond this point it is joined by the stream historically known as Wadi Jabala. The 'Wadi Jabala' is an ancient toponym derived from the name of the
Ghassanid phylarch
Jabala ibn al-Harith, which no longer appears on modern maps. Around after the Allan passes
Hayt it is joined by
Nahr al-Harir (or Ehreir), and after a further the river flowss into the Yarmuk at an elevation of above sea level. ==References==