UK
Race against tide for archaeologists digitally restoring Seaford Head’s ancient hillfort



Sun, January 9, 2022

The Iron Age hillfort at Seaford Head has stood watch over the English Channel from its cliff top location for two-and-a-half millennia - Paul Grover

The Iron Age hillfort at Seaford Head has stood watch over the English Channel from its cliff top location for two-and-a-half millennia. Yet it is doomed to collapse into the sea, with parts of the site already lost and climate change accelerating its downfall. Archaeologists are now in a race against time to unlock its secrets.

Experts from University College London have spent recent weeks surveying the ancient monument with drones and producing 3D models of it in the hope of not only learning more about Seaford Head, but producing a template for the hundreds of other historic monuments along the British coastline set to disappear beneath the waves.

Seaford Head fort, which also contains a Bronze Age burial site (barrow) and dates to around 600 to 400 BC, perches atop the Seven Sisters headland of the same name between Brighton and Eastbourne.

Despite being known to archaeologists for centuries, it has only had investigative work done on it twice, in the late 19th century by Augustus Pitt Rivers and again in the 1980s. These surveys have done little more than date the fort and barrow.

“There are most definitely secrets that it hasn’t given up, because it hasn’t been subject to any major excavations”, Jon Sygrave, a project manager for Archaeology South-East, a part of UCL, told The Telegraph.

This latest survey, which is funded by Historic England, is not designed to reveal those mysteries, so much as identify them and decide what further archaeological work should be done and can be justified with constrained resources.

A key plank of the survey work is drone photogrammetry, which involves taking multiple aerial photographs of the site, merging them using advanced software and georectifying them so that they are to scale and measurable. This allows archaeologists to create a 3D model of the site and identify sites of potential interest.

Drone photogrammetry is a key part of the archaeologist's work to create a 3D model of the ancient monument

The drones are also used to survey the cliff face itself which, due to previous collapses, already provides a cross-section of the fort. “We’ve got one image very clearly showing the ditch and bank of the enclosure,” said Mr Sygrave.

Whatever the results, time and tide are working against his team.

On average, the coast at Seaford is retreating by 50 centimetres (20 inches) a year. That figure, however, masks a pattern of large cliff collapses followed by months or even years of stasis. The UCL team cannot predict when the chalk might next give way, but it could take with it another large chunk of the fort.
Large chunk of cliff collapsed last year

In March 2021, a large section of the Seaford Head cliff face collapsed following heavy rain, leaving behind an enormous mound of debris reaching into the seawater. Elsewhere on the clifftop, large cracks have appeared, portending further losses. That prompted English Heritage to place it on the Heritage at Risk register.

“Every time that there’s a section of cliff that’s lost, it’s not just the material that’s lost in that cliff collapse. There’s also the area behind it, because you can’t safely work within the first 10-20 meters of the cliff,” explained Mr Sygrave.

Climate change, meanwhile, is likely to accelerate this process. Increasingly rough weather conditions and rising sea levels are all expected to eat away at Britain’s coastline and the ancient monuments dotted along it.

Marcus Jecock, a senior archaeological investigator and coastal lead at Historic England, said: “Coastal erosion is not a new threat, but climate change is accelerating the rate at which erosion is happening and thereby the rate at which archaeological sites of all types that exist around our coasts are being lost - often without proper record.”

The coast of Seaford is retreating by 50 centimetres a year

Because of the precarious nature of coastal heritage, the study undertaken by Archaeology South-East at Seaford Head is designed to produce results quickly and cost-effectively. The full survey work was completed in just a few weeks, while a full analysis of the findings will be submitted by the end of January.

The pilot project is also intended to spark a discussion among a general public perhaps unaware of how much of its heritage is about to plunge off a cliff face.

With sea defences potentially costing into the millions of pounds, as well as sometimes being disfiguring, few at-risk sites realistically can be saved from disappearing.

The project will produce a podcast series, bringing in institutions such as the National Trust, as well as films discussing the protection of heritage.

“It’s a discussion that needs to be had between people that manage these sites, curators and the public as well, so that they’re not under any sort of illusion that all of these sites can be protected,” said Mr Sygrave.