How climate change will increase ground risks to property

9th August 2021

In a recent presentation (13th July 2021) in association with the MGAA, Terrafirma’s Dr Tim Farewell – one of the UKs leading academics on the interaction between geohazards and the built environment – spoke with MGAA members about ground hazards and their potential for change under future climate scenarios. Dr Farewell detailed the key risks to property from ground hazards to educate managing general agents on the climate-related ground risks they should be aware of when underwriting for property and land.

On-going scientific evidence shows that globally our changing climate is altering the frequency and severity of physical ground hazards such as subsidence and erosion.

Soil-related subsidence:

From an insurer’s point of view, subsidence is the downward movement of ground and is covered in most buildings insurance policies, alongside heave and landslides. With several potential causes, including local mining history, trees and soil washout, subsidence caused by the shrinking and swelling of (typically clay) soils is the leading cause of subsidence damage in the UK, and was the opening focus of the talk.

Opening with a poll, Dr Farewell asked attendees to select which ground hazard was most likely to impact their business in the future from soil-related subsidence, coastal erosion, sinkholes, and landslides. Just over half (57% of MGAs in attendance) selected soil-related subsidence, and Dr Farewell revealed that this naturally-occurring hazard looks set to cause more problems for residential and commercial property owners and their insurers.

Research conducted by Terrafirma’s soil scientists, geologists and climate scientists that combines UK Climate Projections (UKCP18) with the latest soil moisture modelling suggests that the hotter, drier summers will expose more properties to risk of soil-related subsidence.

“Looking at the transition in property risk, we see that low risk properties are becoming fewer, and the number of moderate to high risk properties are increasing. Research conducted based on Terrafirma’s National Ground Risk Model: Climate™ (NGRM: Climate) reveals that property built on clay soils in the southeast of England will continue to fall victim to subsidence claims and properties in the northeast – where much of the housing stock is built on shallower foundations – are projected to become particularly susceptible under all future climate scenarios.” Dr Farewell explains.

When structural remediation is needed in the claims process, it is important to find cost effective, sustainable method of foundation designs, which produce vastly lower CO2 emissions. Trees in close proximity to property can be a major contributing factor in incidents involving subsidence as they draw moisture from the soil leading to greater shrinkage of the ground, typically leading to differential movement and cracking. Trees however are important in the urban environment to reduce flooding, keep areas cool and provide other health benefits, so sensitive solutions need to be found that allows trees to exist in harmony with buildings in urban areas.

The approach to modelling future claims was discussed. Given the state of flux, historical claim rates and costs to insurers 20 years ago should not be used in insolation as indicators of the risks to property from ground hazards today.  Likewise,  present day data is not a reliable indicator to forecast what will happen in the next 20 or 30 years.

Coastal Erosion:

The erosion of land by the sea is also a concern for property in some coastal areas. Those properties built on ‘softer’ geology types that are susceptible to erosion are particularly vulnerable as they tend to have faster erosion rates that are exacerbated by rising sea-levels.

Using Birling Gap, East Sussex as a case study, Dr Farewell explained that this area is eroding at around 70 cm a year, and discussed the history of erosion at the location, which has seen a row of former coastguard cottages reduce from eight, to three over the last century. Specialist understanding of geology is needed to analyse which parts of the coast are eroding, and those that are not as our climate changes. With 30% of the population of England and Wales living within 10 km of the coast and erosion rates accelerating in some coastal areas but not all, insurers, reinsurers and MGAs should understand where properties are at risk in order to write better business.

Dr Farewell explains that “from a coastal erosion perspective, we want to highlight the properties that are at risk in each decadal time slice. This means we can go from the present day through the next century and highlight those properties that are particularly problematic as we go forward through time. We’re going from around 5,000 properties at risk at the moment to significantly more – up to around 35,000 by the 2080s when looking at RCP 8.5.”

Sinkholes from mines and voids:

The UK is fascinating geologically, and a huge number of mineral resources have been mined for thousands of years. Recent mines are well documented – we know where they are, whereas others that might go back to Neolithic times weren’t recorded at all.

One of the main reasons for mining-related collapses is the haphazard way old mines were capped. Old ways of filling the mine entry relied on filling the void with wood or rubble, which after hundreds of years degrade and collapse. As residents of Ripon will attest, natural voids can also occur and cause problems for property. Ripon is built on top of large gypsum deposits, which is a soluble form of geology. Water in the form of rainfall dissolves the rock and forms large natural cavities underground, which can destabilise the surface and cause massive damage to property. As we see an increase in rainfall due to climate change, it is likely we will see an increase in sinkholes appearing in areas with mining history and soluble geology like chalk and gypsum.


Most people think landslides occur in far and remote mountainous areas, and they’d be largely right. However, from small-to-medium scale slips from railway embankments to large ancient landslides that gradually move over time, landslide risk exists in urban areas too.

A famous example of the latter is Ventnor, of the Isle of Wight, where just recently eight houses were evacuated due to the risk associated ongoing movement.  When a landslide affects a property it can limit a homeowners’ access to insurance and further impact the property’s saleability and value.

National Ground Risk Model: Climate

In a second poll of MGAA members, when asked if they knew what percentage of their book were at risk, or had considered how climate change is going to change that, 80% of members said ‘no’.

For the past 6 years Terrafirma have been at the forefront of helping to educate homeowners and property professionals about the risks the ground pose through expertly-interpreted conveyancing ground risk reports. Terrafirma’s continued research and expert team are now helping financial partners identify risks and realise opportunities for their businesses.

Terrafirma’s NGRM: Climate gives users access to a ground risk profile for any property in Great Britain. Climate projections reveal the risk to property from soil-related subsidence and coastal erosion for every decade between now and the end of the century.   

With this information, insurers’, reinsurers and MGAs can understand the changing nature of ground risks like subsidence and coastal erosion and how they impact their business.

To see the presentation go to YouTube:

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  • Author : MGAA
  • 9th August 2021