OR/14/010 What information does the dataset provide

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Dearden, R A, Tye, A M and Marchant, A. 2014. User guide for the Pipe Leakage Impacts. Nottingham, UK, British geological Survey. (OR/14/010)

Overview

This section describes the datasets included in the Pipe Leakage Impacts map.

Summary map

The summary map provides an overview of the extent to which leakage may increase ground instability. It is derived from the datasets described in Sections below.

Soluble rocks

Some types of ground contain layers of material that can dissolve in water (e.g. from leaking pipes), causing underground cavities to develop. The ground above cavities can collapse, resulting in subsidence. More commonly, water can flush away unconsolidated sediment into dissolution voids, potentially leading to the collapse of overlying materials. Leaking pipes can accentuate dissolution or flushing of fines resulting in more significant impacts around underground assets and adjacent infrastructure.

This component data layer is derived from the soluble rocks (dissolution) layer of the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for ground instability as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/soluble.html.

Landslides

A landslide is an outward and downward movement of material on a slope, due to the force of gravity. A slope is under stress from gravity but will not move if its strength is greater than this stress. If the balance is altered so that the stress exceeds the strength, then movement will occur. If a leak occurs from a pipe or culvert, leaking water could alter the strength of the deposit, leading to a more significant subsidence hazard.

This component data layer is derived from the landslide (slope instability) layer of the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for landsliding as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/landslides.html.

Compressible ground

Many geological deposits contain water-filled pores. When the ground is compressed by a building or other load, the water in the pore space can be squeezed out, causing the ground to compress. This may cause uniform or non-uniform settling, resulting in tilting, cracking or distortion of underground assets. Leakage of water from pipes could alter the strength of the deposit, leading to more significant ground movement.

This component data layer is derived from the compressible ground layer of the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for ground instability as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/compressible.html.

Swelling' clays

Clays susceptible to shrink and swell, change volume significantly according to how much water they contain. All clay deposits change volume as their water content varies, typically swelling in winter and shrinking in summer, but some do so to a greater extent than others. Leaking pipes are a significant contributory factor that can change the moisture content of clay resulting in swelling. This may result in uplift or lateral stress on part or all of an asset; any such movement may cause cracking and distortion.

This component data layer is derived from the shrink-swell clays layer of the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for ground instability as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/shrink_swell.html.

Running sands

Running sand conditions occur when loosely-packed sand, saturated with water, flows into an excavation or other type of void. The pressure of the water filling the spaces between the sand grains reduces the contact between the grains causing them to be carried along by the flow. This can lead to subsidence of the surrounding ground. If a failed pipe is leaking, the flow of water may cause sands to flow, thereby resulting in subsidence of surrounding ground.

This component data layer is derived from the running sand layer of the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for ground instability as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/running_sand.html.

Collapsible ground

Collapsible ground comprises fine-grained materials with large pore spaces. Such deposits can collapse when loaded and then become saturated by water. If the ground below a building collapses it may cause the building to sink. If the collapsible ground is variable in thickness or distribution, structures may suffer from distortion, tilting or cracking. If a pipe leaks, the additional water may accentuate the ground stability issue resulting in more significant hazards.

This component data layer is derived from the collapsible ground layer in the BGS GeoSure dataset. The data layer has been reclassified to provide an indication of the potential for ground instability as a result of pipe leakage. Information about the original dataset can be viewed at: http://www.bgs.ac.uk/products/geosure/collapsible.html.

Data summary

The original datasets used in the creation of the Pipe Leakage Impacts map are detailed in Table 8.

Table 8 Details of the original datasets used in the Pipe Leakage Impacts map.
Data layer Layer ID Original dataset Dataset owner Scale
Summary Summary N/A BGS 1:50 000
Soluble rocks Soluble GeoSure v6 BGS 1:50 000
Landslides Lndslides GeoSure v6 BGS 1:50 000
Compressible ground Compress GeoSure v6 BGS 1:50 000
Swelling clay Swell GeoSure v6 BGS 1:50 000
Running sand Runsand GeoSure v6 BGS 1:50 000
Collapsible ground Collapse GeoSure v6 BGS 1:50 000