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29 October 2014

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Seaton Sluice dunes

Point 1 - The fragile dunes

Between the car park and the beach stands a natural barrier that has taken thousands of years to form. We read how sand dunes have developed, and how important they are to the coastline.

The dunes at Seaton Sluice were originally formed after the end of the last ice age, around 10,000 years ago, as tiny grains of sand were picked up by the wind, blown a short distance, and collected in heaps. 

A plentiful supply of sand was needed for their formation. Some sand would have come from erosion of the coal measures sandstone bedrock, but a ready-made supply was waiting in the form of glacial out-wash. 

This had developed during, and at the end of, the last glacial period as melt-waters charged with rock debris scoured their way through Northumberland's countryside during the advance of the ice.

Seaton Sluice sand dunes
Dunes - thousands of years in the making

It flooded eastwards, dumping sands and gravels along a broad coastal strip. This was the raw material for our dunes.

On the coast, onshore winds, predominantly from the North and North East, would have picked up dry sand grains and gravels on the beach that were exposed as the tide retreated. 

The grains would then have been transported landwards by the wind and dumped at the back edge of the beach where the slope changed. Individual grains moved up the beach in a hopping motion, until they met an increase in the slope, where the wind would have been unable to carry them further uphill. 

Hartley Links grows

"The dunes today represent a fragile environment, once we lose it, it is gone for good. "
Paul Williams, The Open University

They would have been dumped here at Hartley Links, forming a pile that was our infant sand-dune.

Once the dune had started to form, it acted as an obstacle to further wind-collected grains, which were also dumped at this point. Over time, the sand dune grew in size as fresh sand grains were rolled up the windward face and settled in the lee. 

This also resulted in the sand dune migrating inland in the prevailing wind direction. 

They are always on the move, migrating inland. This will be an exaggerated process if there is relatively flat land behind the beach. 

Migration of the dunes can however be arrested if they are colonised by vegetation. 

This stabilisation of the dune-field can happen naturally, but as in the case here at Seaton Sluice, can also be helped by human intervention. Planting of Marram grass is the usual strategy. This grass binds the sand dune and stabilise them. 

Once stabilised, the dunes act as a valuable wild life habitat.  The dunes also have another vital function - protecting the coastline against both flooding and erosion by the sea.

A precarious future

Seaton Sluice sand dunes
Grasses are vital to the dunes future

But this stabilising vegetation is easily damaged. 

Grazing animals can destroy the grass colonies and trample other vegetation. 

Human activity is however the greatest threat to this fragile ecosystem.  Simply walking through the dunes damages the binding plant life irreparably. 

Once this happens, the dunes are subject to migration, and wind erosion.  Wind-scour can generate large hollows, blow-outs, into which neighbouring dunes collapse. 

Due to a shift in climatic conditions these dunes are no longer actively building. 

In fact there are only one or two places in the entire British Isles where sand dunes are currently being formed. 

So here at Seaton Sluice, there is no fresh build up of sand that could repair the damage. 

Once the dune is damaged, the erosion processes take hold and destroy the whole dune. 

So, there is an urgent need to ensure the stability and protection of this unique environment to guarantee the long-term survival of this vital ecosystem. 

The dunes today represent a fragile environment, once we lose it, it is gone for good. 

Paul Williams, The Open University               

You can spur off the dune path down to the beach here, but always be aware of the tides - you can get local tidal information from the links on the right of this page.

From here - walk along the dunes path to appreciate point 2 - the wind turbines of Blyth.

last updated: 04/04/06
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St Mary's Lighthouse. Photo: Ken Cowins

Kielder Water

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