5th September 2019
When buying a house, most purchasers view the transaction as a long-term commitment and investment. In the excitement of buying my first home, I was more interested with the decor and layout of the property than what was below the surface. However, the recent changeable weather patterns have made me reflect, perhaps we should be more concerned about what we can’t see below the ground, what our homes and businesses are built on, as ultimately ‘what lies beneath’ could have devastating consequences in the future.
Subsidence is likely to increase if more extreme weather occurs due to future climate change, and unforeseen effects on a range of ground and property related issues. Recent dry summers in 2003, 2006 and 2018 have caused significant increases in insurance claims for clay-related subsidence. The summer of 2018 showed the largest quarter-on-quarter increase since records began in 2001 (The Insurance Times, December 2018).
Extreme rainfall events are also becoming more frequent. The recent partial collapse of the dam at Whaley Bridge in Derbyshire is an example of the unforeseen effects of extreme rainfall. The dam, which acts a barrier between Todbrook reservoir and the town, threatened to collapse entirely in August 2019, prompting the evacuation of 1500 residents. It has recently been downgraded from a ‘critical’ status and residents have since been allowed to return home as the structure is deemed to no longer pose a risk of collapse. It is unlikely that residents of Whaley Bridge considered the dam as a ‘risk’ when they bought their property, but with extreme weather becoming more frequent, perhaps our perception of risk needs to change to account for such events.
Image 2 shows an ‘earth embankment dam’ similar to Toddbrook Reservoir. Dam’s built in the UK hundreds of years ago did not consider future climate conditions. It is still unclear whether the dam collapsed due to a structural fault or whether the concrete slab fell-in due to a void that has been forming underneath. Considering the recent dry spell followed by excessive rainfall, it is likely that the collapse occurred due to the effects of extreme weather.
“Climate change has possible permanent alterations to Earth's geological, biological and ecological systems”. 
Increased droughts or wetter seasons will increase the likelihood of shrink-well in clay soil and therefore disturbance to building foundations, which may lead to underpinning and repair work needing to be carried out. The Terrafirma Ground Report assesses the potential for clay-related shrinkage using the latest Cranfield University data on the types of soils, their water content and the influence of nearby trees which could affect ground movements. With this information a building surveyor will be able to look for evidence of building or drainage damage that might require repair. The details of any previous repairs should be checked to make sure they have been properly completed and if there has been a previous claim, a check on the insurance status of the property will be needed. Contact us for more information.
Climate change is likely to increase ground instability all over the UK, as safe soil saturation levels are being exceeded through more frequent and intense precipitation. Coal Tips shape the Valleys of South Wales. Notorious for sliding, the tips lie on a bed of highly porous sandstone riven with streams and underwater springs. Unable to drain away, the water remains entrapped within the slope, eventually creating an unstable and unpredictable lubricated mass of soil waste, and a high risk of slope failure for the surrounding residents and infrastructure.
To the residents of Swansea Valley, the possibility of landslides is all too familiar in their day to day lives. Godre'r Graig Primary School, near Neath Port Talbot, was forced to close earlier this year due to serious concerns with the slope stability surrounding a historic quarry spoil after a prolonged period of rain. Locals have renamed Godre’r Graig as “The moving mountain”, which has been causing concern for over a century. In 1966, a Primary School in Aberfan was engulfed by a tragic coal tip Landslide, claiming 144 lives  and devastating an entire village, thought to be the result of several days of constant heavy rain.
Sea level rise is caused primarily by two factors – melting ice sheets and glaciers, and the expansion of sea water as temperatures around the globe rise. Since 1993, sea levels have risen on average by 3.3mm per year, according to the NASA Goddard Space Flight Centre . In addition, 18 of the 19 warmest years on record have all occurred since 2001 and are set to continue into the 21st century. The movement of waves inland exacerbates erosion of the upper and lower profiles of vulnerable shorelines around the UK, and with it, claiming homes, roads and fields with many residents unaware of the risks they face.“A large proportion of the coastline of the UK and Ireland is currently suffering from erosion (17% in the UK; 20% in Ireland) and of the 3,700 km coastline of England and Wales, 28% is experiencing erosion greater than 10 cm per year“ 
Coastal communities and infrastructure are subject to continuous threats from flooding and coastal erosion, which are only set to accelerate further. Frequent unpredictable weather events can cause unprecedented damage to both lives and the local economies, such as storm Xaver in December 2013 which resulted in over £1.6 billion worth of damage and the infamous storm surge of 1953 which killed 307 people in England alone.
A report from the Committee on Climate Change (CCC) states that at present, 8,900 properties are at risk from coastal erosion and by the end of the 21st Century, it is projected to be 100,000+ properties – with a maximum 1m increase in sea level. In addition, it is predicted that by 2080, 1600km of major roads and up to 650km of railway line could be at risk according to the CCC report . Potential damage costs resulting from coastal erosion are estimated at £15 million per year, which in the worst case may rise to £126 million per year by 2080, as predicated by the Foresight Flood and Coastal Defence Project . Ouch! The predicted statistics could have a devastating impact on UK residents and their properties.
Photo 1 and 2: https://www.bbc.co.uk/news/uk-england-derbyshire-49247226
Climate change is, for the most part, unpredictable in its wide-spread effects to the general public. Terrafirma look to inform and educate risks associated with the ground, by interpreting geo-spatial data within our Ground Report which covers ground instability [including assessment of future climate scenarios], in the UK, to better understand the ground and help our clients do the same. Watch this space!
Want to learn more? Join our webinar ‘Investigating Subsidence and a Changing Climate’ on Tuesday 1st October at 11am.
Register your interest here: https://register.gotowebinar.com/register/899762652043398412