The BGS GeoSure Shrink Swell 3D data is a regional hazard susceptibility map that identifies areas of potential shrink–swell hazard, in three dimensional space, at intervals down to 20m in the London and Thames Valley area. Shrinking and swelling clays can change volume due to variation in moisture, which can cause ground movement that may affect many foundations. The data provides an indication of variation in Volume Change Potential (VCP) of shrink-swell clays and is classified on an A-E (low to high) range of hazard susceptibility. BGS GeoSure Shrink Swell 3D for London is part of the BGS GeoSure range of natural subsidence products. It is derived from the BGS Geology 50k data, the BGS London Lithoframe 3D model and the GeoSure v7 Shrink-Swell layer.