Instability problems along Jerash-Amman highway are evaluatedusing two methods: 1) Geographic Information Systems (GIS modeling), and 2) Geomechanical and Structural analysis. The landslide susceptibility map derived from nine contributing parameters using GIS is grouped into five classes of susceptibility levels: very low susceptibility (very stable), low susceptibility (stable), moderate susceptibility (moderately stable), high susceptibility (unstable), and very high susceptibility (highly unstable). The major zone along Jerash Amman highway is the unstable zone. The second major zone is the highly unstable , which is located in the areas 37.933 to 38.833 km, 42.383 to 45.713 km, and 55.443 to 56.003 km south of Irbid. The execution of road cutting should be discouraged in the unstable zone; if unavoidable the problem must be solved. The highly unstable areas have to be entirely avoided and cut roads in other areas. The moderate and high susceptibility zones are the most common in urban and agriculture areas; therefore the present status must be preserved and solve the instability problems.The landslides inventory map was used to validate the GIS model; which proved to be highly accurate (88.52%) for the very high and high stable zones.
For structural models, three sites with different lithology were examined. In site A which is located along the old Amman Jerash highway and 2.6 km from Jerash city, a toppling failure is seen SE at 115° direction. The major size of failure blocks is moderate, and the major filling material is quartz which may cause healing or welding of the joints. In site B which that is located on El Mastaba exit (47.608 Km from Irbid), there is a toppling failure to the west and also to the WSW at 265° direction, and also a wedge failure plunges 76° to 176°. The major size of failure blocks is large, and most of the fillings are marl (decreasing the strength) and calcite (may be dissolved). Site C which is located 34.943 Km from Irbid. Here the toppling failure is at 315° direction, and the wedge failure plunges 70° to 278°. The major size of failure blocks is small, and the major filling material is marl. By comparing the landslide susceptibility maps derived from GIS with the structural stability models; we can confirm their consistency. Site B is the most unstable site is located in the high and very high susceptibility zones. Site A which is moderately stable, located in the moderate and high susceptibility zones. Site C is more stable than other sites. It is located in the moderate and low susceptibility zones