Shifting shores at Birling Gap and the Seven Sisters

White chalk cliffs and the beach at Birling Gap, East Sussex — White cliff views recede into the distance at Birling Gap, East Sussex | © National Trust Images/Chris Lacey

Our coastlines are constantly changing due to rising sea levels, erosion and weathering. These natural processes have been happening for centuries and have shaped Birling Gap and the Seven Sisters into what you see today. These changes present us with unique challenges including those of the safety of our visitors. The geology at these sites are slightly different but both are important for wildlife and vegetation, providing a home for plants and nesting birds. We work with these natural coastal changes to plan for the future in this dynamic landscape.

Erosion at the Seven Sisters

The white chalk cliffs of the Seven Sisters are world famous. The chalk erodes in such a way that large pieces fall away and leave near-vertical faces which create the steepness of the cliffs.

It is not just the action of the sea from below that causes this erosion but also heavy rainfall. Water passes through the chalk and then freezes as temperatures drop. The water then expands and cracks the chalk, causing the cliffs to erode from the top.

Staying safe at Birling Gap

Our white cliffs are beautiful but also very fragile. They may appear safe to stand on, but chalk is a soft rock that can be softened further by heavy rain or undercut by wind and wave action. This means the cliff edge is very unstable and at risk of collapsing at all times. It is unsafe to stand on or near the edge and near the base of the cliffs. Always keep at least 5m back from the cliff edge and the base of the cliff, even when the sun is shining. Be aware of tide times. The sea comes in and out twice a day and often reaches the base of the cliffs so it is possible to get cut off by the incoming tide or forced up against the cliffs with the subsequent risk of drowning. We do not encourage anyone to walk further than 150m either way from the beach platform. Make sure you can always safely exit the beach.

The geology at Birling Gap

At Birling Gap the geology is slightly different, and this can best be seen by looking back at the cliffs from the beach at low tide. The dry valley, underlain with coombe rock, was created during the last Ice Age (which lasted until about 12,000 years ago). As the coombe rock is much softer than the chalk it erodes at a faster rate – about one metre every year - causing a slight ‘bay’ at Birling Gap.

In 2014, the chalk cliffs at Birling Gap suffered seven years’ worth of erosion in just two months, in part due to heavy storms.

Kittiwake in flight above the sea, photographed from above — A kittiwake flying over the sea | © National Trust Images/Dougie Holden

An important habitat

Most of the coastline in the south east of England is either built up or protected through sea defences. This has not happened at the Seven Sisters, which has remained unspoilt due to the long history of National Trust and East Sussex County Council ownership.

These cliffs and the wave cut platform below are nationally and internationally important for their biology and geology. They provide spaces for specialised plants and animals to thrive, as well as being a safe habitat for nesting birds such as fulmars, kittiwakes and peregrine falcons.

Planning for the future

Erosion, rising sea levels and weathering have been happening for thousands of years but the process is now speeding up, possibly due to the effects of climate change. We are taking a long-term view and planning for the future by working with natural coastal change where possible.

There are several practical ways that this has been done at Birling Gap and the Seven Sisters:

The specially designed metal fencing can be moved back in response to any changes in the cliff line and profile. Gabions and other structures have also been designed to be moved when necessary
Part of the café was taken down in 2014, following a large cliff fall, to ensure that the rest of the building remained safe for continued use
A consultation process is being carried out to find out what visitors and local people would like to see at Birling Gap in the future, given the natural changes that the site will undergo

These actions will hopefully provide time and space to manage the ever-changing coastline at Birling Gap and the Seven Sisters, meaning we have a better chance of coping not only with sea level rises but also the impact of extreme weather events.

This ‘shifting shores’ policy can only work through talking to, and working with, coastal communities, other organisations and the government about the importance of working with natural processes.

A sunny view across the blue sea with cottage roofs in the foreground and the white chalk cliffs of Birling Gap and the Seven Sisters in the distance

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People and dogs on wet sand at the beach, with chalk cliffs behind, at Birling Gap, East Sussex

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