Study highlights the complex changes and threats facing Cornwall’s sand dunes

New research carried out by the University has developed a means of predicting dune evolution on a regional scale

Mr Alan Williams

Media and Communications Manager

Corporate Communications (Marketing and Communications)

28 January 2025

Sand dunes are an iconic feature of Cornwall’s coastline and an essential, natural element of the county’s coastal flood defences.

However, new research has suggested they could face an uncertain future in the face of the sea-level rises and increases in extreme storms predicted under future climate change.

The study, by experts in coastal processes at the University of Plymouth, focused on 31 sites along Cornwall’s north and south coasts.

The researchers developed a method through which they could quantify historic changes in the dunes, with the ultimate aim of providing coastal managers and other agencies with predictions about how the dunes might behave in the future.

The results painted a varied picture of how the dunes have been impacted over recent years by some of the most energetic storms ever to hit the Cornish coast.

At Par Sands, on the south coast, the dunes have advanced by around 1metre per year showing that sand from the beach is being blown into the dunes and making them increase in size.

However, at Crantock – on the north coast near Newquay – the dunes had retreated inland by about 3metres a year, likely because of changes in the position of the river channel as it flows over the beach and the action of storm waves.

Writing in the study, published in the journal Ocean & Coastal Management, the experts say the diversity in dune evolution across the study sites highlights the complexity of coastal dune dynamics.

They also say these varied responses emphasise the importance of developing site-specific predictive models that incorporate factors such as sediment supply, the transport of sand grains, the underlying rock surface and estuarine channel dynamics.

Every dune system we studied is unique.

Although most dunes, especially on the north coast of Cornwall, experience volume loss and retreat due to storm erosion, others exhibit accretion and seaward expansion driven by sediment transport by wind. Some sites also show so-called rollover dynamics, where the front of dune retreats, but the back of the dune expands while a few sites lose dune sediment while at the same time advancing seaward. It all demonstrates the complex nature of Cornwall’s sand dunes and the need to assess each in its own right.

Miss Liane Brodie
PhD student on the Making Space for Sand project and study lead author

Current projections about future changes in beaches and dunes, and how they might be impacted by sea level rises, are commonly made using a principle called the Bruun Rule.

It takes into account a range of characteristics, including the shape of the coastal profile, the height of the dunes and the wave climate, to identify the extent of the coastal zone at risk from sea-level rise. When applied to the Cornish sandy beach-dune systems, the Bruun rule predicts a coastal retreat of anywhere between 13m and 61m by 2100.

For many of the sandy beaches along the coast of Cornwall, application of the Bruun Rule using the sea-level rise we have experienced in the past two decades does not match what we have observed. Some shorelines are advancing despite rising sea levels, and others are retreating much faster than predicted. For us, it highlights the importance of considering every dune system on an individual basis rather than providing a generic prediction based on what might occur along a whole coastline. And that, in turn, underlines the importance of coastal monitoring to ensure shoreline predictions are regularly updated using up-to-date coastal observations.

Professor Gerd Masselink
Professor of Coastal Geomorphology

The study was carried out as part of the Making Space for Sand project, a £6million project led by Cornwall Council and a number of partners including the University.

This project is funded by Defra as part of the £200 million Flood and Coastal Innovation Programmes which is managed by the Environment Agency. The programmes will drive innovation in flood and coastal resilience and adaptation to a changing climate.

Cllr Martyn Alvey, Cornwall’s cabinet member for environment and climate change, said:

“This research on our dune systems is vital in helping us understand ways in which we can adapt and become more resilient to climate change while maintaining vibrant coastal communities.”