All change at Selsey, West Sussex, UK
David Bone (UK)
Issue 26 of Deposits magazine in the Spring of 2011 included my article on fossil collecting at Bracklesham Bay in West Sussex, following in the footsteps of my guide book on Fossil hunting at Bracklesham & Selsey, published in 2009. This area has been well known for the foreshore exposures of Palaeogene and Quaternary geology since the mid-nineteenth century and is still very much an area for popular fossil collecting, as well as research. Many readers will have been to Bracklesham or Selsey to collect sharks’ teeth and may have even been lucky enough to find a piece of mammoth bone or tooth.
The scientific value of the area is recognised by much of the coastline being designated as a geological Site of Special Scientific Interest (or SSSI). However, this has been impacted by two major coastal defence schemes at Selsey that were completed in 2013, significantly changing access to the foreshore and any exposures of the geology, as well as rendering my guide book in need of a major update.
In medieval times, Selsey was effectively an island, although this is no longer the case due to the construction of sea defences and land reclamation. However, Selsey remains a localised area of higher land surrounded by low-lying land prone to flooding (Fig. 1). It has also been an area of coastal erosion and loss of land to the sea throughout recorded history. The relatively unconsolidated Palaeogene and Quaternary sediments exposed in the low cliffs of the peninsula were easily eroded, particularly during storms driven by the prevailing south-westerly winds. Rising sea level since the end of the Pleistocene has undoubtedly played a part in this and has been a major consideration in the coastal protection schemes recently completed.
On the west side of the Selsey peninsula, the higher beds of the Selsey Formation (Eocene, Bracklesham Group) were commonly exposed on good low tides when the cover of beach sand had been removed by wave action. Tidal runnels carved in the foreshore exposures provided a supply of fossil detritus for sieving, while the sediments could be sampled for a rich assemblage of mollusc, vertebrate and microfossil material (Fig. 2). A visitor today will find all this dramatically changed. In fact, unfortunately, it has all disappeared.
West of Selsey, towards Bracklesham, a shingle bank is essentially all that protected the low-lying Earnley Marshes, agricultural land and much of the West Sands Holiday Village at Medmerry (apparently the second largest caravan site in Europe) from inundation by the sea. Reconstruction of the shingle bank was regularly needed, but a severe storm in January 1998 resulted in a breach of the shingle bank, with an estimated 30,000 tons of shingle being washed away in around 20 minutes by the force of the waves.
The West Sands Holiday Village was partly flooded to a depth of 0.6m. The cost of reinstating the shingle bank over the one weekend using 18 bulldozers and 40 lorries bringing in shingle from inland reserves was variably reported as being up to £300,000. Winter storms over the following years, with escalating costs of repair, continued to cause concern about the long-term future of the sea defences.
Various plans to remedy the situation were being developed with the favourite – despite local opposition – being a managed retreat and realignment of the coastline inland of the low-lying areas. Public engagement and progress on the proposed scheme was given a significant boost by another severe storm in March 2008 that caused an estimated £5 million of flood damage at the West Sands Holiday Village and required evacuation of the site. Several seafront chalets were severely damaged, while storm waves undercut the concrete seawall protecting houses in Selsey. Subsequently, with full planning permission, Bunn Leisure (the owners of the holiday village) constructed their own coastal protection, which was completed in 2013 at a cost of £16.8 million.
This consists of two larvikite rock groynes (the stone brought by barge from Norway) with 500,000m3 of offshore dredged shingle infilling between them to create a broad artificial beach in front of the site (Fig. 3). This resulted in the complete burial of the former exposures of beds S7 to S9 (Selsey Formation), which were the popular fossil collecting beds at the Selsey end of Bracklesham Bay. Beach sand is also accumulating around the rock groynes, raising beach levels and obscuring previous intermittent foreshore exposures of the nearby beds S6 and S10. On a positive note, the geology still exists beneath the new beach and maybe, one day in the distant future, the sand and shingle will erode to reveal the fossiliferous beds once again.
The situation is dramatically different to the west of the holiday village. Here, the low-lying land behind the shingle bank is of no commercial value apart from rough grazing and arable crops and the responsibility for coastal protection lies with the Environment Agency. It is in this area that the managed realignment of the coastline has been put into action (Fig. 4). Work, at a cost of £28 million, commenced in October 2008, just two months after planning permission had been granted.
A new inland flood bank, 7km long and encircling 183 hectares of low-lying land, was constructed using material excavated from borrow pits and new drainage channels. The flood bank terminates on the foreshore with larvikite rock groynes, 1.5km apart, the foreshore and shingle bank between being left to natural erosion by the sea. In the final stages of construction in September 2013, the shingle bank was breached with a 30m wide excavated channel at the site of the former Broad Rife sluice, the original outfall for the inland drainage system. This allows the sea to flood in on the rising tide, through the complex of channels and former borrow pits, with the expectation that this will gradually form new mud flats and salt marsh. One of the scheme drivers is that this new habitat creation compensates for the loss of similar habitat elsewhere in the UK due to coastal development and rising sea levels.
Shallow excavations associated with the construction works yielded large amounts of archaeological material, principally dating to the Bronze Age, but also including medieval remains and World War II defences, as well as munitions from the post-war gunnery range that operated here. Deeper excavations revealed a thin layer of Quaternary raised beach gravels that provided a rich source of Ice Age erratics, possibly originating by ice-rafting from Brittany and the Channels Islands. One of these – a large mudstone boulder – has been relocated to the RSPB Visitor Centre at Sidlesham and is on display by the car park (Fig. 5).
Now, some three years or more after the breach, the changes are dramatic. The unprotected and no longer maintained shingle bank behind the foreshore is rolling back at around 20m a year, particularly around the breach (Fig. 6). The former, low-lying land behind is submerged at high tide and is rapidly developing into mud flats, as designed. What does this mean to the visiting geologist or fossil collector? Firstly, it is no longer possible to walk the length of the Bracklesham Bay foreshore because of the breach. Even at low tide, the outward flow is too great to risk crossing. However, it is the increased erosion along the foreshore that is now opening new possibilities for the future.
Currently, there are extensive exposures of Holocene deposits (much of it Bronze Age soils and alluvial channels fills), and associated archaeology, walls of long-lost farms and World-War II ordnance. Beneath these are intermittent exposures of Pleistocene raised beach gravels and weathered Eocene beds. But the coastline continues to erode and the area of foreshore will grow and move inland. Who knows what might appear in the years to come? However, there is no obvious impact on the foreshore exposures of the Earnley Formation (beds E3 to E5) at Bracklesham, the regular hunting ground for fossil collectors (Fig. 7).
The newly created wetland area is now managed by the Royal Society for the Protection of Birds (RSPB) as a nature reserve. Because of the private ownership of land and roads in the area, beach access from the west is only accessible from the public car park at Bracklesham or the new reserve car park at Earnley, both long walks to the west side of the breach. Access through the West Sands Holiday Village to the east is now security controlled, so access for the casual visitor is not always easy. However, there is a viewpoint from which the new wetland is best seen at high tide (Fig. 8).
My new, extended 40-page guide-book (Fig. 9) is now available at £4.00 plus £1.30 p&p (at current postage rates) and is reviewed on the page opposite. Enquires to David Bone at: email@example.com.
Bone, D.A., 2016. The geology and fossils of Bracklesham and Selsey. Limanda, Chichester, 40 pp.