Predicting the Risk of Subsidence

CRANFIELD, England, Aug. 20 -- Cranfield University issued the following news release:

'Soil science' and 'insurance' are words not often seen in the same sentence. Nevertheless, soil scientists at Cranfield University have developed an enhanced version of their subsidence model to help insurance companies assess and manage subsidence claims.

The release of this updated subsidence map is extremely timely. This summer is poised to be the worst year for subsidence in well over a decade, with cracks already being found in houses across much of the UK.

Cranfield's soil geohazard models in the Natural Perils Directory (NPD) contributed to the awarding of the Queen's Anniversary Prize for soil science earlier this year. The geohazard models combine soil and weather data to highlight properties most likely to be at risk of ground movement.

With extreme weather events making the headlines, it is more important than ever for insurance companies to be aware of buildings which may be vulnerable to subsidence. This is because when clay soils dry out, they shrink. Clay related soil shrinkage and swelling is the most common and costly form of subsidence in the UK.

Dr Timothy Farewell, Senior Research Fellow in Cranfield's Centre for Environment and Agricultural Informatics, said: "This new, improved version of the Natural Perils Directory can help the insurance industry to understand subsidence, and make better decisions about how to prioritise subsidence claims this summer and autumn. Now that the NPD combines the comprehensive and validated subsidence claims data (from Property Risk Inspection and Airbus Defence and Space) and the location and height of trees in the UK (from Bluesky's National Tree Map), our models are not only more precise, but also provide insurance companies with a way to quantify the impact of subsidence across their whole business."

Soils under some houses can shrink by as much as 20%. How much the soil shrinks is dependent on the type and amount of clay minerals in the soil, the weather and proximity of trees. Some soils contain a lot of shrinking clay minerals, making houses built on them more vulnerable to subsidence. The location of large trees to buildings can also have an enormous impact on the level of moisture in the soil.

The perfect storm for subsidence involves a long, hot and dry summer like the one currently being experienced in the UK, shrinkable soils, older houses which have been extended in recent years and the presence of established, but still growing trees.

To ensure that the subsidence models in Natural Perils Directory are of upmost help to insurance companies, they combine soil, weather, tree and subsidence claims datasets to comprehensively answer the following key questions:

1. How much can the soil shrink?(Data from the National Soil Map)

2. Are the soils likely to dry out?(Weather data for normal and 'extreme' years)

3. How many trees are nearby?(Data from the National Tree Map)

4. Have subsidence claims been reported here before?(Historical subsidence claims)

Dr Farewell added: "As our climate changes towards one with hotter and drier summers, our enhanced NPD models also allow home owners and mortgage companies to assess 20-30 year changes in subsidence risk to properties. This is of particular importance in northern cites, which are becoming drier in the changing climate. These northern cities are where we are likely to see the greatest increase in subsidence claims."