Subsidence and Extreme Weather Raise Landslide Risks on UK Roads and Railways

Leading ground engineering firm Mainmark UK is warning that the same subsidence affecting thousands of UK properties each year is also increasing the risk of landslides and slope failures near roads and rail, particularly as the country experiences more extreme dry–wet weather cycles.

The British Geological Survey’s (BGS) National Landslide Database, which contains more than 17,000 recorded landslide events across Great Britain, shows that landslide activity increases markedly during periods of prolonged rainfall and intense weather, with recent wet winters driving elevated levels of ground instability.

A recent survey from BGS revealed approximately 3,000 slopes across the UK underwent consistent movement annually between 2018 and 2022. In total, the active instability of the slopes affects around 14,000km of roads and 360km of railway, representing 2.4 per cent of the road network and 1 per cent of the railway network nationwide.

Subsidence can contribute to slope instability and movement in several ways. As the ground sinks unevenly, slope angles may increase, reducing natural stability, while cracks and fractures associated with drying clays allow water to infiltrate deeper into the ground, weakening soil or rock strata.

If the ground drops at the base of a slope, the loss of lateral support can trigger sudden slippage, which can damage road surfaces, distort rail tracks, or disrupt transport operations. Subsidence can also alter natural drainage patterns, saturating soils, increasing pore-water pressure and reducing the shear strength that holds slopes in place.

This ground movement is particularly evident in former mining areas across the UK. The collapse or deformation of old underground workings can cause sudden ground movement that destabilises overlying slopes (an issue highlighted in a recent Coal Authority report examining ongoing subsidence liability).

Coastal regions face similar challenges, with Cumbria being a prime example, having reported 41 landslides in the past decade, three of which have been this year. Land settlement and groundwater changes make slopes and levees more vulnerable during periods of heavy rain or storm activity, which are particularly frequent in such areas.

David Hedley, Infrastructure & Commercial Lead at Mainmark UK, comments: “Subsidence is often seen as a problem for homeowners, but the same processes that crack walls and distort floors can also weaken slopes, embankments and shut down travel routes. With the dry–wet cycles we’re now seeing more frequently, we’re urging councils and road authorities to treat slope stability as part of their wider subsidence-risk planning.”

Mitigating the risk requires early detection and proactive ground management, particularly in areas supporting roads and transport corridors. Monitoring ground deformation using satellite data or ground-based instruments can provide early warning of instability that could threaten road surfaces and embankments. Managing groundwater levels and controlling resource extraction help reduce downward pressure on sensitive soils. Improving drainage and, in some cases, reinforcing slopes with vegetation or engineered structures can also strengthen ground conditions and reduce the likelihood of failure.

Mainmark says engineered ground-improvement solutions, such as targeted resin injection or precision grouting, can be used to stabilise soils and restore strength without major excavation, offering a practical option for both infrastructure owners and private property owners.

“Subsidence and slope instability are closely linked,” continues David “With climate patterns shifting, we need to take both seriously if we want to prevent avoidable infrastructure disruption and long-term damage and road closure.”

Mainmark Ground Engineering (UK) Ltd is a subsidiary of the Mainmark group of companies established in 2016, with its headquarters located in Milton Keynes. For over three decades, Mainmark has established itself as a pioneering force in the industry, leading the way in developing and delivering cutting-edge solutions. With an impressive track record of over 200,000 successful projects across Australia, New Zealand, Japan and the UK, Mainmark has earned international recognition as an award-winning ground engineering organisation.