Karst geohazards in the UK: the use of digital data for hazard management

An essential prerequisite for any engineering or hydrogeological investigation of soluble rocks is the identification and description of their characteristic, observable and detectable dissolution features, such as stream sinks, springs, sinkholes and caves. The British Geological Survey (BGS) is creating a National Karst Database (NKD) that records such features across the country. The database currently covers much of the region underlain by Carboniferous Limestone, the Chalk, and particularly the Permo-Triassic gypsum and halite where rapid, active dissolution has caused significant subsidence and building damage. In addition to, and separate from, the identification of specific karst features, the BGS has created a National Karst Geohazard geographical information system (GIS). This has been created to identify areas that may potentially contain karst geohazards. Initially, all the soluble rock units identified from the BGS 1:50 000 scale digital geological map are extracted. Each soluble unit has been given an objective score, interpreted, as based on factors including lithology, topography, geomorphological position and characteristic superficial cover deposits. This national zonation of these soluble rocks can then be used to identify areas where the occurrence potential for karstic features is significant, and where dissolution features might affect the stability of buildings and infrastructure, or where karstic groundwater flow might occur. Both datasets are seen as invaluable scientific tools that have already been widely used to support site investigation, groundwater investigations, planning, construction and the insurance underwriting businesses.