The data comprises four GIS layers representing the permeability of geological deposits for Great Britain (bedrock, superficial, artificial and mass movement deposits). The permeability data has been derived from DiGMap-GB (Digital Geological Map Data of Great Britain), and therefore reflects the scale of DiGMap-GB. For the majority of the Great Britain, the scale is 1:50,000, however in areas where the geology is not mapped to this scale, the next best available scale is used. For bedrock deposits this is 1:250,000 and for superficial deposits this is 1:625:000. Artificial ground and mass movement deposits have not been mapped beyond 1:50,000. The data is updated annually, or after a major new release of DiGMap-GB. The permeability data describes the fresh water flow through geological deposits and the ability of a lithostratigraphical unit to transmit water. Maximum and minimum permeability indices are given for each geological unit to indicate the range in permeability likely to be encountered and the predominant flow mechanism (fracture or intergranular). Neither of the assigned values takes into account the thickness of either the unsaturated or saturated part of the lithostratigraphical unit. The data can be used freely internally, but is licensed for commercial use. It is best displayed using a desktop GIS, and is available in vector format as ESRI shapefiles and MapInfo TAB files.
