SIMPLIFIED LARGE-SCALE LANDSLIDE HAZARD MAP OF JAMAICA:
EXPLANATION OF MAP UNITS
1. AREAS LEAST SUSCEPTIBLE TO LANDSLIDING
Includes: Alluvium and Marshland
Few landslides have formed in these areas. Formation of large landslides is possible but unlikely except during heavy rainfalls and earthquakes. Slopes are generally less than 15 percent, but may include small areas of steep slopes that could have higher susceptibility. If an area is adjacent to a zone area with higher susceptibility (faults), a landslide may encroach into the area, or the area may fail if a landslide undercuts it, such as flat area adjacent to sea cliffs.
2. LOW SUSCEPTIBILITY TO LANDSLIDING
Includes: Exposures of limestone belonging to white Limestone Group and Coastal Group. Several small landslides have formed these regions. Slopes vary from 5-70 percent. Generally stable, however, slope-stability problem may occur as mentioned in 1 above.
3. MODERATE SUSCEPTIBILITY TO LANDSLIDING
Includes: Exposures of clastic sediments of Wagwater Formation and Granodiorite. Many landslides have developed in these areas and are controlled by the presence of steep slopes, planar discontinuities and depth of weathering. Slopes may be greater than 30 percent in sedimentary rocks. Effects of deep weathering are significant in granodiorite areas. These areas are well developed. See 1 above for additional stability problems.
4. MODERATELY HIGH SUSCEPTIBILITY TO LANDSLIDING
Includes: Exposure of cretaceous sedimentary, volcanic and metamorphic rocks and sedimentary rocks belonging to Yellow Limestone Group.
Many large and small landslides have developed in these areas and several of these have caused extensive damage to roads and property. These areas are well developed except for the eastern part of the island. Large landslides are likely here and these areas receive heavy rainfall. Slopes are generally greater than 30 percent.
VERY HIGH SUSCEPTIBILITY TO LANDSLIDING
Includes: Exposures of shale and sandstone sequence belonging to Richmond Formation and andesitic volcanic rocks of New Castle Volcanic Formation. Extensive development of large and small landslides and damage to property, roads and utilities. Lithology, slope angle, planar discontinuities in rock strata, depth of weathering and rainfall all play an important role. Slopes are generally greater than 30 percent in areas of volcanic rocks whereas some areas of shales have gentle slopes. These areas are highly developed, however, some parts are unstable.
6. HIGHEST SUSCEPTIBILITY TO LANDSLIDING
Includes: Landslides and possible landslide deposits.