12th June 2020
For many of us, a coastal home with stunning views across the sea is a dream-come-true. I am lucky enough to be one of those people so I know how wonderful it can be.
However, as three significant coastal landslide events make the news across three counties, it is a stark reminder of how that dream can quickly turn into a nightmare.
The landslides across Devon, Dorset and Kent in recent weeks have made the news and photographs of their dramatic impacts on land and property highlight the risks and potential issues for coastal property owners and prospective purchasers.
As usual there is much speculation about causes (including the slightly improbable suggestion that movements at one site were the result of fossil hunting!), so rather than adding to this I thought it might be helpful to offer somecontext on these issues based on my 25 years of experience dealing with slope instability.
Sea cliffs exist due to instability. The action of waves and storms erodes the coast and forms cliffs. For much of the time this process is gradual, but it is continuous – the White Cliffs of Dover are white because grass does not have time to grow, small amounts of chalk are continually falling from the face. Eventually large movements occur, either as the sea undermines the faces (as for the recent large rockfalls at Sidmouth in Devon), or where the whole slope becomes unstable in weaker materials becoming a landside (such as the landslip in London Clay affecting homes on the Isle of Sheppey).
The rate of erosion of sea cliffs is not consistent. For long periods the erosion of sea cliffs may be very gradual but sudden large movements can occur. This means that looking at the stability of cliffs over the last few years is not a good indicator as to when properties near to them might be affected. Too often we hear of comments like ‘I thought we were safe for another 40 years’ based on this assumption. Normally the types of movement over a long section of coastline over tens or even hundreds of years needs to be considered to fully appreciate the risks.
Coastal erosion cannot be stopped, only slowed down. Very substantial sea defences can be installed to protect sea cliffs from erosion but even they becomedamaged by the action of the sea and need to be expensively maintained. Often the measures to protect the cliff are designed only to slow the rate of erosion and do not protect against severe events such as very large storms. The cost of installing or maintaining sea defences is normally beyond most homeowner’s resources and in any case the extensive planning and environmental controls may rule them out.
Insurance may not cover the damage from coastal erosion. Where there is a history of coastal erosion insurance may be declined. However, even where properties are insured then there can be exclusions which make claims difficult since the damage to properties may be classed as damage from erosion, storms, sea or landslide – as a case in Hemsby, Norfolk has highlighted. Dependent on the policy, it is possible that properties may be uninhabitable or inaccessible without suffering direct structural damage, which can be claimed on insurance policies. Without insurance cover, homeowners may even be liable for the costs of removing material that has collapsed onto the shore.
All of this means that special care needs to be taken when buying properties near to the coast. Houses with lovely sea cliff views are unfortunately those where there might be at significant risk from coastal erosion, as the recent ‘Living On The Edge’ campaign from Confused.com brings into focus. The types of coastal instability can be complex and not obvious to the untrained eye, and even where there are sea defences, these may not be sufficient or even being maintained. In addition to the usual enquiries, early specialist advice is therefore essential.
The Terrafirma Ground Report includes records of large landslides and information on coastal erosion and the plans for maintaining sea defences are available via the local Shoreline Management Plan. However, specialist geotechnical advice should always be sought if this information highlights any concerns about long-term stability or there is any evidence of ground movement.
Finally, as always, check that insurance is available to comprehensively covers the risks from coastal erosion, landslide, sea and storm damage.