Insight User Guide: Ground cavities and sinkholes

Natural cavities

Industry recognised national database of natural cavities. Sinkholes and caves are formed by the dissolution of soluble rock, such as chalk and limestone, gulls and fissures by cambering. Ground instability can result from the movement of loose material contained within these cavities, often triggered by water.

This data is provided in point and polygon format. Where the ‘Data Type’ in the data table is classified as ‘polygon’, this indicates an area-based record, and that natural cavities are found somewhere within this area, but not necessarily beneath the property itself. The polygon areas can be large, so caution is advised in the interpretation of this data.

Mining cavities

Industry recognised national database of mining cavities. Degraded mines may result in hazardous subsidence (crown holes). Climatic conditions and water escape can also trigger subsidence over mine entrances and workings. The cavity data have been collected from a diverse range of sources such as published information (e.g. technical papers, cave and mine guides, books etc), unpublished information (e.g. library and museum archives, academic studies, consultant and contractor archives etc), district and county councils, British Geological Survey and many others.

The database includes mines excavated for the extraction of non-ferrous metals (e.g. fluorite, calcite and barytes), rock (e.g. slate, chalk, limestone, oil-shale, fullers’ earth and non-coalfield fireclays), iron (non-coalfield) and evaporites (e.g. salt and gypsum).

Reported recent incidents

This data identifies sinkhole information gathered from media reports and Groundsure’s own records. This data goes back to 2014 and includes relative accuracy ratings for each event and links to the original data sources. The data

is updated on a regular basis and should not be considered a comprehensive catalogue of all sinkhole events. The absence of data in this database does not mean a sinkhole definitely has not occurred during this time.

Historical incidents

This dataset comprises an extract of 1:10,560, 1:10,000, 1:2,500 and 1:1,250 scale historical Ordnance Survey maps held by Groundsure, dating back to the 1840s. It shows shakeholes, deneholes and other ‘holes’ as noted on these maps. Dene holes are medieval chalk extraction pits, usually comprising a narrow shaft with a number of chambers at the base of the shaft. Shakeholes are an alternative name for suffusion sinkholes, most commonly found in the limestone landscapes of North Yorkshire but also extensively noted around the Brecon Beacons National Park.

Not all ‘holes’ noted on Ordnance Survey mapping will necessarily be present within this dataset.

BGS National karst database

This is a comprehensive database of national karst information gathered from a wide range of sources. BGS have collected data on five main types of karst feature: Sinkholes, stream links, caves, springs, and incidences of associated damage to buildings, roads, bridges and other engineered works.

Since the database was set up in 2002 data covering most of the evaporite karst areas of the UK have now been added, along with data covering about 60% of the Chalk, and 35% of the Carboniferous Limestone outcrops. Many of the classic upland karst areas have yet to be included. Recorded so far are: Over 800 caves, 1300 stream sinks, 5600 springs, 10,000 sinkholes.

The database is not yet complete, and not all records have been verified. The absence of data does not mean that karst features are not present at a site. A reliability rating is included with each record