Millions of homes and properties could face subsidence in the coming decades as a result of climate change, the British Geological Survey has warned.
New maps from the RGS show the growing threat of damage to properties from shrinking and swelling of the ground without action to tackle greenhouse gas emissions, with London and the South East most at risk.
The analysis uses data on potential ground movement and long-term rainfall and temperature scenarios to project the impact of climate change from 1990 up to 2030 and 2070 under a worse-case scenario.
It finds that the number of properties across Britain highly likely or extremely likely to be affected by “shrink-swell” could rise from 3% or nearly one million in 1990 to 6.5% or more than 2.4 million in 2030.
By 2070, almost 11%, or more than four million properties, could be highly or extremely likely to face subsidence issues.
Shrink-swell refers to changes in soil volume due to moisture changes in the ground, which could worsen as the UK faces more weather extremes as a result of rising global temperatures.
When clay-rich soils absorb lots of water, for example in wet weather, it can cause the ground to rise and structures to lift, which is known as heave, while in warmer, drier weather, soils can become very hard and the ground shrinks and cracks, causing subsidence.
The most susceptible areas are London, particularly northern and central boroughs and Kent in the South East, the analysis finds.
Patrick Gray, BGS head of digital products, said the analysis highlighted the areas most vulnerable to shrink-swell subsidence due to climate change.
“This is important information that can help communities and property owners to build resilience to future climate change,” he said.
In London, the number of homes and buildings highly or extremely likely to be affected could double from a fifth – more than 840,000 – back in 1990 to 43% or 1.8 million by the end of this decade.
By 2070, almost 2.4 million properties, some 57% of buildings in the capital, are very likely to face problems if greenhouse gas emissions remain high.
BGS geological engineer Lee Jones said, in the South East, many of the clay formations are too geologically young to have been changed into stronger mud rocks, leaving soil vulnerable to absorb and lose moisture.
“Added to that, Britain is seeing increasingly variable climates. In summer 2018 for example, we experienced some of the warmest and driest summer months in years, whereas 2019 was one of the wettest on record.
“Dry weather and high temperatures are a major factor in the emergence of shrink-swell subsidence and looking to the future, these increases in annual temperatures and variability in rainfall are very likely to continue.”
Subsidence can lead to financial losses for property owners, expensive remedial work, increased insurance premiums, lower house prices and even impacts on infrastructure such as transport and utility pipes.
But the BGS said property owners could take steps to limit the potential effects, such as seeking specialist advice before starting any major building work.
And they should be aware of the effects of laying drives, paths or hardstanding that is impermeable to water, and of planting or removing trees close to properties, which can all have an impact on soil moisture levels.