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Landslide Susceptibility Assessment for ST. Thomas, Jamaica.The parish of St Thomas in Jamaica is highly prone to slope failure and in the past this has resulted in extensive damage and in some cases loss of life. To reduce the effect from landslides, there was an urgent need to map and assess areas that may be prone to future failure. Aerial photographs coupled with geomorphological field mapping were used to inventory the landslides. The factors conditioning the slopes for failure were assessed and a weighting value assigned to them. The weighting was achieved by using the principle of Bayesian conditional probability. The weighted factors were combined in a Geographical Information System (GIS) to produce a landslide susceptibility model for the study area. The susceptibility model created is in general agreement with the distribution of landslides in the area. Comparison of the model with the existing landslides showed that 97% of the landslides fell within the high and very high susceptibility zones of the model. Comparison of the model with landslides that occurred during 2002, and that were not used in the construction of the model, shows that 83 of the 89 slides that occurred fell within the high and very high susceptibility zones. The landslide susceptibility model created hopefully will be one of the first steps in looking at the risks landslides pose to lives, developments, whether it is housing, agriculture or the physical infrastructure and may be used to guide land-use planning in the parish
Landslide susceptibility mapping in North-East WalesIn North-East Wales, United Kingdom, slope instability is a known environmental hazard which has caused significant damage to the built environment in the recent past. This paper reports on the creation of a digital landslide inventory for North-East Wales and the use of a Geographical Information System (GIS) to create landslide susceptibility models that are applicable to landslide hazard management in the area. The research undertaken has resulted in the most comprehensive landslide inventory of North-East Wales to date, documenting 430 landslides within the area. Landslide susceptibility models created within a GIS using a statistical (multiple logistic regression) approach, divide the landscape of North-East Wales into areas of ‘low’, ‘moderate’ and ‘high’ landslide susceptibility using calculated probability values. These models indicate that 8% of the surface exposure of drift deposits and 12% of the area of solid geology is of high or very high susceptibility to slope instability. Validation tests have demonstrated the accuracy of these models and their potential value in a predictive sense. The digital landslide database and susceptibility models created are readily available to interested stakeholders, and may be useful tools in land-use planning, development of civil contingency plans and as guidance for the insurance industry.
Landslides in Jamaica: Distribution, Cause, Impact and ManagementJamaica has one of the highest natural hazard risk exposures in the world, with more than 90% of the population exposed to two or more natural hazards. The island of Jamaica is particularly prone to multiple hazards, including hurricanes, earthquakes and slope instability, due to its geographical position (within the track of Atlantic hurricanes and its location on the Caribbean ‘tectonic’ plate) and its topography and geology (steep slopes with highly weathered material). Of these hazards, slope instability is the most common, affecting not only mountainous areas but also the coastal plains, where submarine landslides have been known to generate tsunamis. One such tsunami contributed to the destruction of the then capital city of Port Royal in 1692. Landslides are predominantly triggered by seismic activities and heavy rainfall associated with hurricanes and tropical depressions. These landslides have caused loss of lives, widespread destruction to the built and natural environment and long-term damage to the socio-economic development of the country. The slope instability problem is compounded by the lack of awareness of the impact by the general public, developers and planners, as well as uncontrolled and unplanned urbanization on marginal lands susceptible to slope failure.
Rainfall Thresholding and Susceptibility assessment of rainfall induced landslides: application to landslide management in St Thomas, JamaicaThe parish of St Thomas has one of the highest densities of landslides in Jamaica, which impacts the residents, local economy and the built and natural environment. These landslides result from a combination of steep slopes, faulting, heavy rainfall and the presence of highly weathered volcanics, sandstones, limestones and sandstone/shale series and are particularly prevalent during the hurricane season (June–November). The paper reports a study of the rainfall thresholds and landslide susceptibility assessment to assist the prediction, mitigation and management of slope instability in landslide-prone areas of the parish.