Sinkholes – a risk to consider

Dramatic collapses have appeared in various British towns and cities, sometimes with little warning, posing a serious threat to public safety, infrastructure, and essential services.

As climate change increases the frequency of extreme weather events and ageing infrastructure continues to deteriorate, sinkholes are likely to become more common across the UK.

While the likelihood of sinkholes is confined to certain geological formations and external conditions, they are an increasing risk that should be on the radar of public service organisations.

What is a sinkhole?

A sinkhole is a depression or hole in the ground caused by the collapse of a surface layer. In the UK, they typically occur in areas rich in soluble rock like limestone, chalk, or gypsum. Over time, water erodes these rocks, creating underground voids. When the ground above can no longer support its weight, it collapses.

Sinkholes can vary in size from a few feet to several metres, both wide and deep. They may appear gradually or suddenly open up, swallowing roads, buildings, and utilities.

How do they form?

Sinkholes in the UK generally form through:

Natural erosion (Karst processes)

• Rainwater, slightly acidic due to carbon dioxide in the atmosphere, seeps into the ground and dissolves the underlying rock.

Other triggers

• Burst water mains or sewer pipes can wash away supporting soil.
• Old mine workings – common in parts of Wales, Yorkshire, and the Midlands – can collapse.
• Construction activity and heavy rainfall can destabilise already weakened ground.

Where do they form?

While the exact number of sinkholes that have appeared in the UK over the past five years isn't readily available, it is known that the British Geological Survey (BGS) lists more than 10,000 sinkholes in their National Karst Database. 

Sinkholes can form anywhere, but are more likely in areas where limestone and chalk are prevalent, such as in the Mendip Hills, the Peak District, the Yorkshire Dales, the South Downs and parts of Wales, especially around Brecon. Ripon in North Yorkshire is known as one of the UK’s most sinkhole-prone towns, due to the gypsum-rich ground conditions, a gypsum dissolves rapidly in water.

Areas historically associated with coal, tin, and copper mining, such as South Wales, North East England, Yorkshire and the Humber, the Midlands, and Cornwall are all vulnerable. The BGS also maintains a national dataset of mining hazards, which can help identify risk zones and aid planning.

How damaging can they be?

In 2025, a sinkhole in Godstone, Surrey, linked to a burst water main, forced the evacuation of 30 homes, and in December 2024, a 40ft sinkhole appeared on a housing estate in Merthyr Tydfil.

In 2023, a social club in Swansea was forced to close when a giant hole opened up in the car park, and a sinkhole on the pitch at AFC Wimbledon postponed a major football match.

While the immediate damage to roads and nearby properties might seem obvious, sinkholes can also cause significant disruption and financial loss in other ways, including road closures and diversions, by damaging water, gas and electricity supplies and restricting access for emergency services.

The potential impact on public sector organisations

Sinkholes present a real and growing risk. Proactive risk management, including regular site assessments, drainage maintenance, insurance readiness, and emergency planning, is essential. Potential impacts on public sector organisations include:

• Local government – sinkholes can disrupt roads, parks, and public buildings.
• Housing – social housing providers must ensure tenant safety and structural integrity.
• Higher education – university campuses with historic buildings may be especially vulnerable.
• Blue light services – emergency response routes and station infrastructure must remain secure.
• Health & social care – hospitals, care homes, and clinics must be protected from ground instability.

What if someone is to blame?

Pursuing a recovery of costs following a sinkhole can be complex, but there are several legal avenues available depending on the cause.

Burst water mains – Under Section 209 of the Water Industry Act 1991, water companies are strictly liable for damage caused by an escape of water from a freshwater main. This means there is no need to prove negligence, and recovery may include property damage, alternative accommodation, and business interruption.

Old mine workings – If the sinkhole is linked to historic mining activity, recovery may involve claiming against former landowners or mining operators where liability can be established This can be done with support from public bodies such as the Coal Authority or local councils.

Top tips

If a sinkhole appears, there are four key steps to follow:

1. Secure the area immediately

• Keep people and vehicles away.
• Use barriers or signage to prevent access.
• Do not attempt to inspect the sinkhole yourself.

2. Notify the authorities

• Call 999 if there is immediate danger to life or property.
• Report the incident to the local council, utility providers, and building management.
• Contact National Highways or the relevant local highways authority if relevant.

3. Evacuate if necessary

• If the sinkhole is near a building, evacuate occupants pending a structural assessment.
• Ensure vulnerable individuals are prioritised.

4. Contact your insurer

• Notify your property or liability insurer immediately.
• Insurers will typically arrange for a loss adjuster to assess the damage and may fund temporary accommodation or emergency repairs.