Methodologies & Limitations: Subsidence data 

The natural ground subsidence assessment is based on the British Geological Survey’s GeoSure data. GeoSure is a natural ground stability hazard susceptibility dataset, based on the characteristics of the underlying geology, rather than an assessment of risk. A hazard is defined as a potentially damaging event or phenomenon, where as a risk is defined as the likelihood of the hazard impacting people, property or capital.

The GeoSure dataset consists of six data layers for each type of natural ground subsidence hazard. These are shrink-swell clay, landslide, compressible ground, collapsible ground, dissolution of soluble rock and running sand.

Each hazard is then provided with a rating on its potential to cause natural ground subsidence. This rating goes from A-E, with A being the lowest hazard and E being the highest. Groundsure represents full GeoSure data as either Negligible (ratings of A), Very Low (ratings of B), Low (C), Moderate (D) or High (E). 

Where GeoSure Basic is instead used, ratings are displayed as Negligible-Very Low (A or B ratings), Low (C) or Moderate-High (D or E). The GeoSure data only takes into account the geological characteristics at a site. It does not take into account any additional factors such as the characteristics of buildings, local vegetation including trees or seasonal changes in the soil moisture content which can be related to local factors such as rainfall and local drainage.

These factors should be considered as part of a structural survey of the property carried out by a competent structural surveyor. For more information on the “typical safe distance” trees should be from a property please see this guide:
www.abi.org.uk/globalassets/sitecore/files/documents/publications/public/migrated/home/protecting-your-home-from-subsidencedamage.pdf