How is Devil's Dyke managed?


1. What will it look like?
Landscape changes – Currently the land on the west side of the Valley is spring and autumn pasture. Flooding will change this into saltmarsh with creeks and some areas of intertidal mudflat. Saltmarsh is very beautiful, particularly in summer, and aids in absorbing the force of the tides. Mudflat is an incredibly rich habitat which supports a great diversity of wildlife. As more silt is deposited each time the land is inundated, ground levels ‘warp up’ so that saltmarsh vegetation can spread. The Cuckmere Valley supports a range of habitats from shingle to grazing pasture. Allowing the sea to inundate one area will simply create another habitat and increase diversity.

Damage to existing archaeological interest – The landscape of the Cuckmere Valley has been evolving for many years, and this project will provide a unique opportunity to gain valuable insights into previous landuse. If evidence of former settlements are found, full record will be made, and flooding the area is actually likely to preserve any remains. Archaeologists will be present at all stages of the engineering works to make sure no damage is done to any existing archaeological interest and to record details about the structure of the floodbank itself. Any documentation, maps or old photographs of the Valley would be useful in building up an historical record of the area.

2. Why is this scheme necessary?
Planned vs unplanned – Maintaining the flood defences within the Cuckmere Valley at their current height will not succeed in the long term given the fact that sea levels are rising and storms are likely to become fiercer and more frequent through climate change. During winter 2000, the sea overtopped the banks on several occasions, damaging the floodbanks and increasing water levels higher up the valley. The sea regularly overtops the river bank at the mouth; put simply, the banks are now too low. It is highly likely that a catastrophic storm event will occur again which will have devastating impacts on the farmland, wildlife and on land further upstream. Restoring the Valley to a naturally evolving ecosystem will mean that the intertidal habitats which will be re-created will act as natural defences to further storm events..

3. How will access and recreation on the valley floor be affected?
Rights of way/ Access - An established Right of Way along the western side of the river would unfortunately be lost through the proposed breach. However, access to the beach will be maintained through two other footpaths within the valley, and a licensed footpath on the hillside to the west of the valley could be upgraded to a full public right of way. This would afford fantastic views across the Valley (be consistent with the use of capitals) and would provide a similar circular route to that which would be lost. The Vanguard Way which runs from the Golden Galleon pub to the beach will be improved by moving sections up onto the 4 m contour, raising it above flood level and making the whole footpath much drier. Access to and understanding of the estuary will be enhanced overall through the installation of interpretation panels to explain the changes to the landscape and the associated wildlife they are likely to encourage. Bird hides are also planned to help people enjoy and appreciate the wildlife at close quarters.

Recreation - Up to half a million people visit the Seven Sisters Country Park every year to enjoy the peace and natural beauty of the area, walk, camp and to see the wildlife. . Canoeing is a very popular activity based at Seven Sisters Country Park and any scheme will take full account of the needs of canoeists, and it may well be possible to retain areas of none tidal water for beginners somewhere within the scheme. Other recreational activities will also be much enhanced. The re-created intertidal habitats will attract large numbers of birds and animals, including some more unusual species like ospreys and seals, and we would like to provide bird hides and interpretation panels within the Valley to enhance people’s enjoyment and understanding of the area. The restoration of a naturally evolving estuary will also have huge potential for increasing the value of the site for education and research..

4. What are the other benefits of this scheme?
Climate change/ Rising sea levels – Climate change is an issue of particular concern in southern England. An increase in rainfall, the gradual sinking of south-east England and a rise in sea-level of as much as 6 mm per year is moving the low water mark landwards. However, sea defences prevent the subsequent landward migration of the high water mark so that intertidal habitats are being squeezed out. This means that low lying land is at greater risk of flooding, as intertidal habitats like saltmarsh and mudflats form excellent natural sea defences, absorbing the power of the waves and acting as a buffer zone.

Flooding upstream - A feasibility study into the flooding implications of this scheme has been carried out with encouraging results. It concluded that because of the increased use of the natural floodplain for storing flood waters, the risk of flooding upstream would be reduced in certain conditions. However the work needs to be carefully phased and monitored, using the latest in sophisticated modelling techniques as they become available.

The capacity of the floodplain on the west side of the river is about 600,000 cubic metres on a high tide. In a severe tidal surge it could exceed 1 million cubic metres. How far upstream the impact of this storage will reduce the depth of water will depend on the type of storm (the combination of rainfall and tide).

The long term aspirations to return the river to the meanders and to remove the walls at the mouth of the river will require much more detailed modelling. However we hope that because more water will be going through the mouth of the river on every tide, the mouth should keep itself clear through the increase in scour.

5. What effect will it have on the wildlife in the area?
Damage to existing ecological interest – The ponds and ditches on the valley floor are home to some nationally important species, most notably water beetles. Although flooding the Valley will mean that some of these important habitats will be lost, similar habitats will be recreated further upstream. Phasing of the project will allow the wildlife to adapt gradually to its new environment, and to move into new niches further upstream.Long term prospects include creation of more saltmarsh as well as other important intertidal habitats such as mudflats. In terms of birds, the re-created intertidal habitats will suit the species already there, but will attract in greater numbers and more species. .

Importance of new ecology – Intertidal habitats like mudflats and saltmarsh are declining across the country, particularly in the south east. This is a significant loss to both wildlife and to our natural coastal protection. The importance of intertidal habitats is recognised by the listing of saltmarsh, mudflats, saline lagoons and vegetated shingle as priority habitats under the UK Biodiversity Action Plan and as habitats which the UK has international obligations to protect. The first phase of the project will create about 46 hectares of intertidal mudflats and saltmarsh and it is likely that a new saline lagoon will be created. In the long term, removing the training walls at the mouth of the river will increase the extent and range of vegetated shingle habitat and lagoons, and re-opening the meanders would further diversify the river and establish new freshwater habitats.

Intertidal habitats are declining across the country, particularly in the south east. This is a significant loss to both wildlife and to our natural coastal protection. The importance of intertidal habitats is recognised by the listing of saltmarsh, mudflats, saline lagoons and vegetated shingle as priority habitats under the UK Biodiversity Action Plan and as habitats for which the UK has international obligations to protect. The first phase of the project will create approximately 45 hectares of intertidal mudflats, which will gradually develop into saltmarsh. Removing the training walls at the mouth of the river will increase the extent and range of vegetated shingle habitat and lagoons, and re-opening the meanders would further diversify the river and establish new brackish habitats.

6. What will happen to the meanders?
The old meanders are a ‘national landscape icon’ but they are at significant risk of being lost completely if the Valley is maintained in its current state. As there is little water flowing through them, they are silting up and they may also be at risk of eroding away completely in the event of a ‘catastrophic bank failure.’ It is believed that the best way of maintaining them indefinitely is to restore the natural processes that formed them originally and the landscape setting that they formed in. The land around the meanders is much higher than the west side of the Valley and will therefore form saltmarsh very quickly. The meanders will briefly disappear under the water on the very high tides of each month but will otherwise remain high and dry for most of the time, looking much the same as they do now.

7. How will the meanders be reinstated?
1. The restoration of the meanders flow, and dredging of silt (without them eroding which is likely to involve establishing saltmarsh vegetation around them before completely opening them to the elements),
2. The relocation of the canoe barn and facilities,
3. Changes to the footpath network (the concrete track to Foxhole cottages is not affected)
4. Numerous ecological issues,
5. Possibly relocating the mouth of the river,
6. Minor revetments to the A259 road, and
7. Other issues that have been raised already and those that haven’t.

8. How will this affect farming on the Cuckmere valley?
Perception of retreating from agricultural land – The need for better coastal protection, especially in the south, has meant that reclamation of inter-tidal areas for agricultural purposes is becoming much less frequent, and agricultural practices are starting to change, recognising that low lying land needs to evolve to adapt to the current environmental conditions, particularly rising sea levels. There are a number of grant incentives for farmers and landowners to create habitats like saltmarsh, and such a grant is being applied for in this case. The Countryside Stewardship Scheme will provide financial support for the land to be managed as mudflat and saltmarsh, and the farmer concerned will be compensate for the loss of grazing pasture on the Valley floor. Light grazing of the saltmarsh may be required in the long term, as this can be highly beneficial to both vegetation and the associated wildlife.

Farming – The valley floor to the west of the river is currently leased to a tenant farmer who grazes the pasture. The National Trust have been working closely with the farmer to establish how best to secure his livelihood whilst providing sufficient coastal protection for the area and enhancing wildlife. Phasing the restoration of the Valley will allow the farmer to gradually alter his stocking levels and adapt to the changing environment. Although the grazing pasture would be lost, the Countryside Stewardship Scheme will ensure that there will be no financial loss to the farmer.r.

9. How will the public be consulted over these changes?
The Environment Agency has announced that it will be submitting a planning application for its proposals to restore the Cuckmere Estuary. The decision to seek planning permission follows extensive consultation with the community over the past two years. The planning application will be submitted to Lewes District Council in June 2003. If planning permission is granted, work could begin to protect the valley as early as autumn 2003. In addition, the critical importance of involving local people and interest groups in the scheme is recognised and many events have already been held, such as guided walks, information boards, roadshows talks and the publication of the "Back to Nature" booklet. The proposed scheme has already evolved to incorporate comments from local groups and the partnership will continue to consult and engage with the local community as the scheme develops.

10. What will be the impact on tourism?
1. Because there have been so few projects of this kind in the past, it is very difficult to establish the impact that this will have on tourism / visitor numbers.
2. Most people come to see the cliffs and meanders – and both of these will remain.
3. The Concrete track to Foxhole cottages will remain above sea level, and there will always be access to the beach (although it will probably be on a different route after phase 2)
4. All of the natural estuaries in the South West / Cornwall / Devon etc don’t seem to put people off visiting them.

11. Are there any other implications of this scheme that I haven’t already been told about?
Erosion/ coastguard cottages – One of the long term aims of the restoration project is to remove the training walls from the mouth of the River and to allow the Cuckmere to act completely naturally. This is likely to mean that the mouth will migrate eastwards, meeting the sea beneath Haven Brow. The movement of shingle along the coast from west to east is likely to build up a bar of shingle across the mouth of the Haven. This build up of shingle will help to protect the cliffs below the Coastguard Cottages, thus providing them with better protection from the sea. Prior to any works taking place however, geomorphological experts who will be able to accurately predict the development of the Valley, will be brought in to make sure we have a clear picture of how the beach will evolve.

Sustainability – working with nature, will mean that coastal protection and flood defence along the River Cuckmere will be sustainable into the future with little or no intervention from man. This clearly has huge cost saving advantages as well as providing peace of mind for people living and working in and around the Cuckmere Valley. It is predicted that once the restoration project is complete, and the River is allowed to migrate across the Valley floor, little if any, works will be needed to protect the area from flooding.

Cost – The Environment Agency currently carry out a number of annual operation and maintenance activities for the lower Cuckmere. These include bank reinstatement, beach recycling and removal of shingle from the mouth of the River. Due to the pressures of sea level rise, the estimated cost of rebuilding the existing floodbank on the west side of the river up to a sufficient standard is approximately £1.2 million. This is because the banks are simply not big enough to cope with rising sea levels. This is clearly not cost efficient, nor would higher and wider banks be fitting with the landscape. Allowing the Cuckmere and the Valley to evolve naturally through the restoration project will save the Environment Agency, and in turn the tax-payer, thousands of pounds. The National Trust are currently applying for a grant under the Countryside Stewardship Scheme which will pay for the majority of the engineering works associated with the restoration and will contribute towards a management plan for the Valley.

 


Copyright Sussex Downs Conservation Board 2000