Enviro + Geo Insight - GIS Schema: Natural ground subsidence
The information below details all definition of each of the layers in the Natural ground subsidence group within the GeoPackage, defining each data layer, the attributes of the data and their data types, as well as the definitions for any values that use look up tables
Shrink swell clays
Layer name: Natural_Ground_Subsidence-Shrink_Swell_Clays_BGS
This is a polygon based dataset describing the potential hazard presented by soils that absorb water when wet (making them swell), and lose water as they dry (making them shrink) across England, Wales and Scotland. This shrink-swell behaviour is controlled by the type and amount of clay in the soil, and by seasonal changes in the soil moisture content (related to rainfall and local drainage). The data is based on 1:50,000 scale digital maps of superficial and bedrock geology, and the BGS's expert knowledge of how geology behaves. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (5) |
| legend | Varchar (200) |
Running sands
Layer name: Natural_Ground_Subsidence-Running_Sand_BGS
This is a polygon based dataset describing the potential hazard presented by rocks that can contain loosely-packed sandy layers that can become fluidised by water flowing through them across England, Wales and Scotland. Such sands can ‘run’, removing support from overlying buildings and causing potential damage. The data is based on 1:50,000 scale digital maps of superficial and bedrock geology, and the BGS's expert knowledge of how geology behaves. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (1) |
| legend | Varchar (200) |
Compressible deposits
Layer name: Natural_Ground_Subsidence-Compressible_Deposits_BGS
This is a polygon based dataset describing the potential hazard presented by natural deposits that could compress when a load (such as a building) is placed on them or they become saturated with water. The data is based on 1:50,000 scale digital maps of superficial and bedrock geology, and the BGS's expert knowledge of how geology behaves. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (1) |
| legend | Varchar (200) |
Collapsible deposits
Layer name: Natural_Ground_Subsidence-Collapsible_Deposits_BGS
This is a polygon based dataset describing the potential hazard presented by natural deposits that could collapse when a load (such as a building) is placed on them or they become saturated with water. The data is based on 1:50,000 scale digital maps of superficial and bedrock geology, and the BGS's expert knowledge of how geology behaves and its origin. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (1) |
| legend | Varchar (200) |
Landslides
Layer name: Natural_Ground_Subsidence-Landslides_BGS
This is a polygon based dataset describing the potential for landsliding (slope instability) to be a hazard based on 1:50,000 scale digital maps of superficial and bedrock deposits, combined with information from the BGS National Landslide Database and scientific and engineering reports. The landslide hazard is controlled by particular slope characteristics (such as geology, gradient, sources of water, drainage, man-made constructions) combining to cause the slope to become unstable. Downslope movement of materials, such as a landslide or rockfall may lead to a loss of support and damage to buildings. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (1) |
Ground dissolution of soluble rocks
Layer name: Natural_Ground_Subsidence-Ground_Dissolution_of_Soluble_Rocks_BGS
This is a polygon based dataset describing the potential hazard presented by ground dissolution, which occurs when water passing through soluble rocks produces underground cavities and cave systems. These cavities reduce support to the ground above and can cause localised collapse of the overlying rocks and deposits. Britain has four main types of soluble or 'karstic' rocks; limestone, chalk, gypsum and salt.The data is based on 1:50,000 scale digital maps of superficial and bedrock geology, and the BGS's expert knowledge of how geology behaves. Records include the assigned class as well as a description of the hazard based on the class.
Geometry: Polygon
Coverage: England, Scotland and Wales
Schema:
| Column name | Data type |
| gs_id | Integer |
| class | Varchar (1) |