BVI CUT SLOPE VULNERABILITY AND STABILITY MAPS: TOOLS FOR SAFER DEVELOPMENT AND RECOGNITION OF HAZARDOUS CONDITIONS

The regional geometric patterns of systematic joints in the BVI were established and used determine the natural slope vulnerability in order to create GIS based Landslide Susceptibility Maps based on orientation and angle relative to joint set planes and intersection wedges. The original QRAP Landslide Susceptibility Maps pertained only to natural slopes and did not address the more serious problem of cut slope failures in the BVI. The UNDP R3i project sponsored the development of the GIS Rock Cut Slope Vulnerability And Stability Maps based on the joint orientation and inclination data that was collected for the QRAP landslide vulnerability analysis and subsequent field studies. Cut slope vulnerability was based on the number of joint measurements inclined in any given direction. Stable recommended cut slope angles were based on the inclination angle of planar joints and joint wedge intersections in the cut slope direction. Vulnerability and stable recommended cut slope angles were also separated by formations, rock type and location. R3i also co-sponsored workshops on the BVI: Understanding your Building Site and How to Excavate for Safe Development. Outcomes of workshop were that contractors and excavators left with the new sense that “SOLID” is not necessarily STABLE and how to recognize unfavorably oriented joints that cause instability. A major achievement! All participants left with the understanding that the consequence of over cutting unstable rock slopes is hazardous, difficult and expensive to remedy, and can be avoided with adequate preliminary design based on the information presented in the new GIS Cut Slope Stability Maps. The UNDP R3i program has provided funding for development of similar maps and workshops for the islands of Saint Maarten and Anguilla.