Sea defences 'raise floods risk'

Up to 61% of coastlines have steepened over the last century

Building sea defences could leave some coastal areas of England and Wales at greater risk of flooding, a report says.

Coastal scientists from Halcrow Ltd looked at 1,000 locations in the first study of its kind in the UK.

They found 61% of the shorelines and beaches had steepened over the last century because of man-made defences.

The report, in the Royal Geographical Society's Geographical Journal, says steeper beaches allow more destructive waves to pound the coastlines.

"The narrowing and steepening of shorelines leads to an increase in the amount of wave energy hitting our sea defences. This can lead to structural damage and overtopping," it says.

Natural functioning

According to the study, the worst affected area was southern England.

The authors claim that structures such as sea walls and promenades prevent the natural functioning of coastal environments.

This is particularly marked on open coasts, where promenades and sea walls have been built across formerly wide sandy beaches, or in estuaries where low lying areas have been reclaimed for agriculture behind sea walls.

One of the authors, Dr Nigel Pontee, a senior coastal scientist at the Halcrow Group Ltd, said: "These results have considerable implications for deciding on future coastal management options around not only the UK, but also, potentially, the rest of the world.

"If we are not to spend increasingly large amounts of money on sea defences, we need to allow more room for coastlines to function as nature intended them to."

The study suggests that holding defence structures in their current positions will not be sustainable in the long term.

As beach widths decrease and water depths increase in front of structures, they will no longer be able to offer the same levels of protection without further investment.