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Coastal landslide mapping of the Black Ven Spittles complex, CharmouthLandslides are not generally perceived as natural hazards that significantly affect the UK. However, slope instability affects many parts of Britain including the Dorset and Devon coastline. Black Ven Spittles is a classic landslide complex along this coastline, exhibiting some of the largest and most dynamic landslips in Europe. It has a long history of instability with significant events occurring as recently as 2008 when a succession of rock falls occurred towards the western side of the complex, uncovering waste material from the old town tip. With the beach adjacent to the landslide regularly used by tourists, fossil hunters and locals for recreational activities, it is of paramount importance that landslides be mapped to determine the active areas. Such mapping may be used for effectively managing the risk posed for this landslide complex. Through field and geospatial mapping techniques utilising remote sensing imagery and Geographical Information Systems (GIS), the most updated geomorphic map of the landslide complex is presented. The maps produced as a result of this research identify how the ‘system’ has changed since 1996 when the most comprehensive geomorphic map prior to this research was published. The most active section of the landslide complex is near the village of Charmouth, which is popular with tourists and fossil-hunters. By identifying this increasing risk, management can be better informed and the public made more accurately aware of this natural hazard
Evaluation of the use high resolution satellite Imagery to map slope instability in a tropical environment: St. Thomas, JamaicaLandslides are a major natural hazard in Jamaica, and have resulted in loss of life, major economic losses, social disruption and damage to public and private properties. There is a need to delineate areas that are prone to slope instability in order to mitigate their effects. The first and most important stage for the creation of a landslide risk maps is the collection of accurate landslide data in a timely manner. However the type of terrain makes landslide mapping particularly difficult. Aerial Photographs have proven to be an effective way of mapping landslides but acquiring new photographs to map recent landslides is very expensive. High resolution satellite imagery were evaluated for their effectiveness in delineating landslides. The landslides on a whole had no distinctive spectral property; hence no one classification technique could be used to identify them. This research developed integrative methods utilising a combination of: edge enhancement to delineate the scarps area; Wetness Index to identify back titling blocks and debris flow lobes where moisture is higher; shape classification (to distinguish from e.g. ground cleared for agriculture); and slope curvature to map scarps. The information from the image classification was combined in a GIS and automated to determine the probability of the presence and or absence of a landslides. Data derived was validated against detailed field mapping at a scale of 1:5000. For more recent landslides, the modelling proved to be effective, accurately identifying 91% of the landslide both in terms of the location and extent. For the older landslides Pre 2000) the mapping was less effective, with misclassification as high as 24% particularly for smaller landslides. However, the use of these imagery does have great potential as they prove useful for mapping new landslides quickly and efficiently after landslide disaster and are much cheaper and quicker to acquire.
Geographical Information Systems (GIS) applied to landslide hazard zonation in the North Wales coalfieldIn areas with a history of slope instability problems, landslide hazard zonation is increasingly becoming an integral tool in the effective management of this hazard (Chauhan et al., 2010; Leventhal and Kotze, 2008; Fells et al., 2008; Moreiras, 2005). Landslide hazard zonation provides the scientific basis for the implementation of land-use, emergency management and loss reduction measures in landslide-prone areas (Haubin et al., 2005). Although such techniques are commonly used worldwide in the management of slope instability, their use has been limited in the UK to a number of localised studies; e.g. South Wales coalfield (Halcrow and Partners, 1989) and Derbyshire Peak District (Thurston, 1997). It has been recognised that there are numerous relict landslides throughout the UK, which are being reactivated due to climatic factors (Arnell and Reynard 1996; Collison, 2000; and Environmental Agency, 2010) as well as land-use changes (Norbury, 2002; Smith, 2002). As indicated by Glade (2003, p3) ‘Land-use change has been recognized throughout the world as one of the most important factors influencing the occurrence of rainfall-triggered landslides’. Hazard mapping and susceptibility modelling (zonation) in landslide-prone areas should be a vital component of land-use planning, particularly where development continues to spread onto slopes deemed unstable. This paper outlines the development of a landslide susceptibility zonation model for areas of solid geology in the North Wales Coalfield and Halkyn Mountain. The model has been validated and has the potential to be utilised in land-use planning at a local and regional level
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.