THE sand dunes on a beach in the north of Scotland are retreating by up to five feet a year and protective measures are urgently needed, according to a scientific study.

The study says Golspie beach in Sutherland should have the type of defensive work successfully carried out in other places such as St Andrews, with a new ridge and gravel and boulders brought in to protect the coastline from further losses.

It found that the upper beach in the northern section at Golspie had eroded at an average rate of up to 3.28ft a year, and the southern section had retreated at an average rate up to 4.92ft a year.

Scottish Natural Heritage, which commissioned the paper, said the erosion was due to rising sea levels as a result of climate change and other factors.

Man-made hard coastal defences further up the coast from Golspie have reduced the supply of natural materials to the area to help combat the effects, the study said.

The work was carried out by Dr Jim Hansom and James Fitton of the University of Glasgow's department of geographical and earth sciences, who went back 134 years in their investigations. They studied historical OS maps dating from 1879, 1907 and 1971 augmented by aerial photography and ground survey from 2013.

The researchers recommended using aggregate, known as 'beach feeding', as a low-cost and effective way to manage erosion and flood risk at key points of the coast.

Dr Hansom said: "Beach feeding would provide natural beach material to the eroded sections by working with natural processes, rather than against them, to mitigate future erosion and flood risk."

He said the supplied material should be mainly coarse gravels and boulders from gravel ridges of the Golspie spit, nearby commercial quarries, or recycled from the beaches to the south.

The paper was commissioned after a storm that affected much of the east coast in December 2012.