Two-thirds of the coastline of England and Wales is at serious risk of erosion and flooding, according to a report to be published this week by the Royal Geographical Society.
Beaches are disappearing and the risk of flooding grows ever more serious, says the report, the first complete analysis of the way the coastal shelves are deteriorating.
The study, which appears in the prestigious Geographical Journal, suggests that sea defences and entire communities may have to be abandoned as the coastline crumbles under the scouring action of the waves.
The threat is posed by a phenomenon known as "coastal steepening", in which the gentle slope of the land as it moves under water becomes an ever-sharper incline. The result is that the low- and high-water marks are moving closer together in 61 per cent of coastal locations. The south of England has seen the most significant changes.
According to the co-author, Dr Nigel Pontee, a coastal scientist at the Halcrow Group consultancy, the process can make waves much more damaging to the coast. The sharper gradients boost the force of waves and the volume of water, according to his research.
The study also found that sea walls are making the situation worse by preventing high tides moving inland naturally. Instead, the tides are being squeezed by the sea wall defences, making some narrow, unprotected sections of the coast more vulnerable than ever.Reuse content