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This page was updated on 8th July 2026.

An economic form of sea defence, in use on selected lengths of coastline for over 40 years. There are worldwide examples. It seems to have become popular within government departments and agencies, probably because of its relatively low cost per metre of coastline, when compared to concrete and steel structures. The latter require careful attention to foundations.
Much has been written on rock armour effectiveness in high storm conditions. Not being a rigid structure it does not suffer from fracturing, but it does move during severe storms, as well as modifying the local wave climate. The latter is a significant factor in the various breaches along the Slapton Line.

Peer reviewed articles, and there are many, point to advantages and disadvantages of the methodology, particularly in times of extreme waves. Nearly all writers explicitly note that its use on mobile sediments such as shingle ridges and beaches is problematic. This is because its placement on mobile sediment is not sustainable.

Specific problems on mobile sediments, such as shingle ridges and beaches, include:
   scouring of the underlying sediment,
   gradual displacement of boulders to lower down a beach,
   settlement of individual boulders into the deeper levels of the sediment.
It has to be remembered that sediments have interstitial spaces which when filled with sea water enable the whole mass to behave as a fluid. Gravitational forces then take control and density differences result in internal movement and sorting.

Rock armour is only a temporary sea defence solution. It is cheap for construction companies to install as fewer qualified and experienced construction employees are required. Companies that bid for this type of work are now labelling their employees "coastal engineers". Qualifications in geology, geomorphology, physics, fluid dynamics or coastal processes may not exist, hence the labels, can be misleading.

Placement on solid foundations such as wave cut platforms of solid bedrock can provide longer lifespans, but all rock armour is temporary. It does require regular maintenance because of winter storm displacement of boulders.

On economically valuable industrial locations, such as the Easington Gas Refinery on the Holderness Coast of Yorkshire, there are less public complaints about aesthetic aspects. However, at places which have a significant coastal resort reputation, or residential value, there are complaints about:
   loss of beach amenity,
   colour and texture of rock being different to local geology,
   the interstices (gaps) between boulders becoming depositories for flotsam brought in by rough weather.
Health and safety concerns arise when children play on the boulders and experience injuries.
In relation to Torcross, there would be almost complete loss of the popular beach.

The whole topic can be pursued easily with internet searches. Keeping to web sites with a published identity is likely to be more reliable than social media. Web pages with an engineering bias may wish to advance positives, but a detailed report, assembled in 1994, by Hydraulics Research Wallingford, provides a balanced perspective. Up until the 1990s HR Wallingford was a Government agency and conducted much of the coastal defence planning work following the North Sea Floods of 1953. Part of that work included site selection for the Thames Barrier, including the physical aspects of the Lower Thames environment. Many of those staff had academic qualifications in their specialisms.

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