BGS Permeability Index version 8

The BGS Permeability Index dataset V8 is derived from the 4 geological themes of BGS Geology 50k: mass-movement, artificial, superficial deposits and bedrock. Each polygon in the BGS Geology 50k is attributed with a 2-part code; LEX-RCS code (rock unit-lithology combination). The LEX-RCS code is assigned (attributed) with 3 further codes to indicate the Predominant Flow Mechanism, and the Maximum and Minimum Permeability. The dataset was produced by dissolving the individual themes of BGS Geology 50k based on LEX-RCS and joining to a Microsoft Access lookup table of all the LEX-RCS combinations with their assigned permeability codes. The first code 'Predominant Flow Mechanism' indicates how fluid will migrate from the ground surface through the unsaturated zone of each rock unit and lithology combination and has three classes: Intergranular, Fracture or Mixed (intergranular and fracture). The second and third codes (Maximum and Minimum Permeability) indicate the range of flow rates likely to be encountered in the unsaturated zone for each rock unit and lithology combination to which five classes have been assigned for the Maximum and Minimum Permeability codes: very high, high, moderate, low, and very low. The Maximum and Minimum Permeability values represent a likely permeability range for the specified rock unit and lithology combination at, and immediately below, its outcrop or subcrop (rather than at any significant depth). The Maximum Permeability represents the fastest potential vertical rate of migration through the unsaturated zone likely to be encountered in the specified rock unit-lithology combination. The Minimum Permeability represents the minimum, and in some cases more normal, bulk rate of vertical movement likely to be encountered. Where a widely variable combination of lithologies occurs within a rock unit this Minimum Permeability value reflects the probable movement rate likely to be encountered in the least permeable horizons. These 3 codes were ascribed solely on the known hydrogeological characteristics of the various lithologies, considering their age, dissolution potential, degree of cementation/induration and fracturing. In unconsolidated deposits, intergranular flow is the predominant flow mechanism. In most consolidated sedimentary rocks, and igneous and metamorphic rocks, fracture flow will occur and hence a wide range of permeability values can occur for any one lithology. The potential for dissolution and degree of cementation, lithological variation and induration are also factors that affect measured values.

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services