Sand dunes on the northern coasts of Devon and Cornwall have been eroded by up to 15 metres in the past 15 years, according to new research.

A study by members of the Coastal Processes Research Group at the University of Plymouth demonstrated that the vast majority of coastal dunes in the South West experience chronic erosion.

Using survey data from 25 dune systems they found that they have been retreating at an average rate of 0.5 to 1 m per year, with only a few dunes in relatively sheltered locations being stable or growing.

This equated to a total retreat over the 15-year period of anything between five and 15 m, with the three worst affected locations being Westward Ho! in North Devon, and Porthcothan and Porthkidney in North Cornwall.

Writing in the journal Marine Geology, the researchers say that for half of the retreating systems, the amount of sand within the dunes has actually increased.

This means sand from the dune face, as well as from the beach, is being transported over the top of the dunes by a combination of wind and waves, and causing the dune system to migrate landward.

This is referred to as ‘dune roll-over’, and means there will be no immediate loss of dune habitat. However, if the dune is pushed back into coastal infrastructure or defences it will be squeezed and that could reduce the dune area.