S. BHALAI – Landslide susceptibility of Portland, Jamaica
of landslide susceptibility zones.
AREA (%) 15
DISTRIBUTION Alluvial plains, northern coastline
Northern half of parish, area east of Rio Grande valley
Western river valleys, west side of Rio Grande valley, extreme upper slopes of Blue Mountain
Upper slopes of Blue Mountain, east side of Rio Grande valley
Table 9. Spatial
AREA (km )
Negligible to Low
Patchy distribution, areas centre of parish, east side of Rio Grande valley
Figure 18. Landslide Susceptibility of Portland. Five the increase in influence of the predisposing factors of
zones of increasing susceptibility are chosen. These show landslides
continue to decompose long after the mass has failed. As these minerals decompose, the mass and volume of the Colluvium correspondingly change making the material unstable. There was no correlation between the distance from geological faults and landslide distribution. The distance between adjacent faults was not appreciable because of the dense network and nearly all the source areas were located in close vicinity to a fault.
The susceptibility model generated has the ability to predict nearly 80% of known landslides which were not initially incorporated into the inventory for analysis. This is highly acceptable considering that the zone of moderate landslide susceptibility predicted nearly all of the remaining source areas.
The model generated is intended for use by civil engineers, planners, developers, disaster managers, other professionals and citizens. Guidelines affixed to the model assist the user in understanding and appreciating the level of landslide susceptibility of each zone. These guidelines indicate the spatial distribution of the zones and present an expert’s opinion as to the general size of landslides that may occur. Geotechnical problems that may arise and recommendations including possible mitigation measures are included. This is particularly important for contingency planning and gives an understanding of the economic requirements and outlays necessary for the mitigation measures that may be needed if development proceeds in a particular zone.