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Published on : Tuesday, November 8, 2016
Researchers have observed that the erosion rate of chalk cliffs at Beachy Head and Seaford Head in East Sussex over the past 150 years has been of 22 to 32cm a year. They have calculated that in the past 7,000 years it was just two to six centimetres a year.
The cause of the huge acceleration is likely to be human management of the coastline, which has stripped some cliffs of their protective beaches, as well as changes in storm intensity. Climate change, which is bringing higher sea levels and fiercer waves, will make the erosion even worse, say scientists.
Dr. Martin Hurst, at the University of Glasgow, who is leading the new work, said that, they are surprised at the stark difference. He also mentioned that, if there is a nice thick and wide beach in front of a cliff, it reflects wave energy. But the beaches have all disappeared.
Coastline management near Seaford, which saw the use of groynes or the shifting of sand and gravel to try to protect specific beaches, has led to the cliffs to the east, including Beachy Head, being starved of sediments.
Prof Rob Duck, at the University of Dundee, who was not part of the research team said that, human s have significantly altered this coastal system.
The scientists were able to calculate the historic erosion rates by measuring the amount of an isotope of beryllium in the rock platform under the cliffs. This isotope is formed in the top few metres of rock when it is struck by cosmic rays from space and the longer the rock is exposed, the higher the concentration. This enables the estimation of the speed of the cliff’s retreat.
Dr Dylan Rood, from Imperial College London, one of the co-authors said that, the coast is clearly eroding, and Britain has retreated fast. A nearly tenfold increase in retreat rates over a very short timescale, in geological terms, is remarkable. He also added that, the UK cannot leave the issue of cliff erosion unresolved in the face of a warming world and rising sea levels. Cliff erosion is irreversible; once the cliffs retreat, they are gone for good.