Dynamic coastlines and shifting shores at Birling Gap

Our coasts are constantly changing through actions such as rising sea levels, erosion and weathering. These are all part of the natural processes that have been happening for centuries and have shaped Birling Gap and the Seven Sisters.

The chalk cliffs of the Seven Sisters are world famous.  Their ‘whiteness’ is due to the chalk that forms the majority of the cliffs.  When the chalk erodes it does so in such a way that large pieces fall away and leave near vertical faces which helps create the steepness of the cliffs. It is not just the action of the sea from below that cause this erosion but also heavy rainfall.  Water passes through the chalk when it lands on the surface and then freezes as temperatures drop.  The water then expands and cracks the chalk, causing the cliffs to erode from the top.

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.  It is a dry valley underlain with coombe rock.  This valley was created during the last Ice Age (which lasted until about 12 000 years ago).  The coombe rock is much softer than the chalk and so it erodes at a faster rate, causing a slight ‘bay’ at Birling Gap.

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 thanks to the long history of National Trust and East Sussex County Council ownership.  These cliffs and the wave cut platform below are important both nationally and internationally for their biology and geology. They provide spaces for specialised plants and animals to thrive, and also a safe habitat for nesting birds such as fulmars, kittiwakes and peregrine falcons.

These changes have been happening for thousands of years but the process is now speeding up, probably due to the effects of climate change.  The early winter of 2014 saw some five metres of cliff erode in front of the café at Birling Gap.  This means that seven years’ worth of erosion effectively happened in just two months.

The National Trust is taking a long-term view and planning for the future by working with natural coastal change where possible.  There are a number of practical ways that this has been done.  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 also taken down in 2014 to ensure that the remainder of the building remained safe for continued use.  A consultation process is currently being carried out to assess what visitors and local people would like to see at Birling Gap in years to come given the changes that the site will undergo.  This will enable us to continue providing a valuable service and welcome to all our visitors for years to come. 

These actions will hopefully give us the time and space to manage our coastal properties with the ever-changing coast line, 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 be effective through talking to and working with coastal communities, other organisations and the government about the importance of working with natural processes.