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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
Landslide hazard mapping and impact in the Holywell area of NE WalesLandslide hazard within urban environments in the UK is largely attributable to two distinct, but not mutually exclusive, types of landslide activity: i) relict landslides in the landscape that predate urban development, and whose presence may or may not have been known about at the time of development; and ii) new slope movements that postdate urban developments. Significant efforts have been made to delimit and categorise the hazard posed by relict slides through, for example, demarcation of known landslides on 1:50 000 maps produced by the British Geological Survey and the compilation of regional databases of landslide activity produced as part of the UK national landslides survey (e.g. Jones and Lee, 1994). This survey showed that much of the relict landsliding in the UK was originally the product of significant climate and environmental changes that followed on from the end of the last (Devensian) glaciation, and that many of these features are now stable in the British landscape, but with the potential to be reactivated either through human mismanagement and/or deteriorating environmental conditions; e.g. changing rainfall patterns linked to climate change (Jones, 1993; Arnell and Reynard 1996; Collison et al., 2000; Environment Agency, 2010). The mapping of landslide susceptibility beyond these relict features is far less complete within the UK, and varies in terms of the methodologies used. One common characteristic of many smaller scale studies is the assumption that the location and type of relict landsliding in an area can be extrapolated to identify new areas with similar geological and geomorphological characteristics that might be susceptible to failure in the future (Siddle, 2000). This assumption is explored in this paper with reference to the physical evidence for landslide damage within a moderately built up area of NE Wales. The research utilises the spatial analysis capabilities of Geographical Information Systems (GIS) to produce slope susceptibility maps using hazard controlling parameters identified from relict landslides, and then explores the relationship between the relict and anticipated landslide hazard with physical evidence for landslide impact upon aspects of the built environment.