Coastal Erosion and Coast Protection

Portland West WearesPortland West WearesThe Jurassic Coast is a beautiful, interesting and internationally important place because it is eroding. Indeed, coasts are a product of erosion. Without the sea eating into the land we would not have a coast at all. An obvious statement but one that needs to be expressed as most people's instant reaction to a landslide or a storm is that it is a 'bad thing'. On the Jurassic Coast, erosion exposes the rocks and uncovers the fossils. These are two of the key features upon which World Heritage Site status was granted by UNESCO. The third are the very processes of erosion itself, the geomorphology; landslides, beaches, coves, sea caves, arches and sea stacks. The iconic Durdle Door is a product of erosion. One day it will fall down and there is nothing we can or should do about it. Indeed, the interest on the Lulworth coast is that you can see every stage in the formation of bays and headlands. The caves in Stair Hole may one day form a new Durdle Door while the stumps of the Bull, the Cow and the Calf are all that remains of previous outcrops that could well have included a former Durdle Door thousands of years ago.

A rock fall, April 2005 and just one year later, April 2006 where no sign remains due to the winter storms washing the material awayA rock fall, April 2005 and just one year later, April 2006 where no sign remains due to the winter storms washing the material away

The future of Durdle Door. There is no question mark here; this will happen sometime in the future! It could be next year or not for 100 years, only time will tell.The future of Durdle Door. There is no question mark here; this will happen sometime in the future! It could be next year or not for 100 years, only time will tell.

The view east from Lyme Regis over the Spittles in March 2008.The view east from Lyme Regis over the Spittles in March 2008.The same view in May 2008: 300 m of the cliffs collapsed in a huge landslide. Since then many amazing fossils have been rescued from the beach as the sea has washed away the mud.The same view in May 2008: 300 m of the cliffs collapsed in a huge landslide. Since then many amazing fossils have been rescued from the beach as the sea has washed away the mud.As the sea erodes the coast, it can lead to landslides that may obscure important rock outcrops or alternatively, a storm could sweep away an old landslide or beach to reveal part of the rock sequence that has not been seen for many years. Similarly, the fossils are uncovered by erosion but that process is completely unpredictable and we therefore cannot tell where the next major find may be. That is both frustrating and exciting, but finding these fossils requires the investment of a great deal of time and for collectors and scientists to be available to respond, instantly to the storms and landslides. A weather forecast with the phrase 'there is a risk of flooding and structural damage' is music to the fossil collector's ear!

This is a dynamic and exciting coastline and the overriding principle in its conservation is that it is maintained by natural processes.

Coastal Conflicts

The construction of the new sea defences at Charmouth in the mid '90’s. ‘The sea has more time and energy than any local authority’ Brunsden 2011The construction of the new sea defences at Charmouth in the mid ‘90’s. ‘The sea has more time and energy than any local authority’ Brunsden 2011There are potential conflicts between protecting the World Heritage Site by allowing it to erode and protecting people, property and infrastructure located on the coast from that very erosion. The coastal towns and villages are as much of an attraction to people as the natural coastline and it is these places where people live and tourists stay and access the Site. Not surprisingly, many people choose to live here and the towns and villages are where they own property or run businesses that provide an income. Many are historically important and contain Conservation Areas and Listed Buildings or scheduled ancient monuments.

Branscombe sea defences. Are the beach huts more important than the naturally eroding coast?Branscombe sea defences. Are the beach huts more important than the naturally eroding coast?When we talk about 'protecting the coast' we are talking about protecting it from coastal defences but when engineers talk about 'protecting the coast' they are generally talking about protecting it from erosion by constructing or maintaining coastal defences! What is more important: the World Heritage Site or the built environment? In reality it is the job of the planning system to balance all of the interests.

The Shoreline Management Plan is a high level strategic document that charts out the future management of the coast for the next one hundred years. The plan takes a holistic approach to the coast so that the management in one place does not cause problems in another. There are only four basic options for management:

Sidmouth. The Shoreline Management Plan says ‘Hold the line’ here because the value of the property defended by the sea wall makes the investment worth while.Sidmouth. The Shoreline Management Plan says ‘Hold the line’ here because the value of the property defended by the sea wall makes the investment worth while.Hold the existing line of defence. This enables the operating authorities, typically the District Councils or Environment Agency, to continue to maintain the sea or flood defences. Examples include the sea frontages of Exmouth, Sidmouth, Seaton, Lyme Regis, West Bay, Chesil Cove, Weymouth and Swanage where the value of the property clearly makes holding the line worth while. As the World Heritage Site does not extend along the fronts of most of these towns, there are usually no conflicts with this policy, although managing the transition between the defended coast and the naturally eroding coast can be problematic and lead to conflict.


Gun Cliff, Lyme Regis. This is an example of ‘Advance the Line’ where the sea wall has been moved forward of the old sea defences.Gun Cliff, Lyme Regis. This is an example of ‘Advance the Line’ where the sea wall has been moved forward of the old sea defences.Advance the line of defence. This allows for the line of the defence to be moved seaward if it is the best way to manage the issue. These are quite rare but Gun Cliff at Lyme Regis is a good example where, in the mid 1990's West Dorset District Council combined forces with South West Water to build seaward of the towns old, historic sea walls (a Grade II listed structure) in order to protect the old town and make the space for a sewage pumping station.

Chapman’s  Pool, Kimmeridge and the Lulworth coast beyond . As with most of the  open coast, there is no conflict here between coastal erosion and the  need to protect property or infrastructureChapman’s Pool, Kimmeridge and the Lulworth coast beyond . As with most of the open coast, there is no conflict here between coastal erosion and the need to protect property or infrastructureManaged realignment. This can relate to realigning the existing defences or the property and infrastructure at risk. Parts of the Exe Estuary provide an example where flood defences constructed to protect farmland are being breached to allow the sea to flood back in which will reduce flood risk to the built environment and create valuable new wildlife habitat.

No active intervention. Not surprisingly, this option applies to most of the World Heritage Site as there are no conflicts with property or infrastructure. As with Hold the Line above, the issues typically arise where the edges of these towns and villages come into contact with the natural, eroding coastline.

Coastal defence schemes are constrained by three factors; they have to be cost effective, viable and environmentally acceptable. A coast defence scheme currently has to cost no more than 20% of the value of the property that it seeks to protect. It also has to guarantee to do the job over its design live (i.e. work) while minimising the impact on the natural interests; the geology, wildlife or landscape. DEFRA now also require schemes to work with nature rather than against it. That means moving away from concrete sea walls and rock armour towards that use natural processes to deliver the required defence through, for example, beach management.

Two Shoreline Management Plans cover the Jurassic Coast:

South Devon and Dorset SMP

Poole and Christchurch Bays SMP

Implications of the SMP review

The SMP's were reviewed and republished in 2011. As they identify future provision for coastal defences they essentially identify areas of potential conflict with the natural interests of the Site. In the short term (up to 2025), all of the existing sea defences will be maintained and there are some conflicts with the natural interests in a few of these areas. There are also a few areas where new defences may be required and these could create a significant conflict with the natural interests. However, in the medium and long term (2025 to 2100) many marginal coast defence schemes will no longer be maintained because of the cost and increasing technical challenges presented by continuing erosion and potential impacts of climate change. So long as the transition is handled well, the quality of the World Heritage Site will actually improve over time but there will be a need to manage the loss in terms of property and infrastructure.

Charmouth in 2009, 2050 and 2100. The coast is going to change. © Original image Plymouth Coastal Laboratory. Manipulation, Jurassic Coast Pathfinder Project 2011.Charmouth in 2009, 2050 and 2100. The coast is going to change. © Original image Plymouth Coastal Laboratory. Manipulation, Halcrow and Jurassic Coast Pathfinder Project 2011.

The coastal Pathfinder

In 2009 DEFRA funded a project through Dorset County Council, in partnership with Devon County Council, to look at managing the transition from hold the line to no active intervention identified by the SMP. Six sites across the World Heritage Site were chosen as case studies to 'road-test' adaptive measures for the time when property and infrastructure start to become at risk. These are still a long way off while the exact or even approximate date for 'change' cannot be predicted simply because that change is not gradual but catastrophic. A sea wall may last much longer than its design life, so the 2025 date when coastal policy changes is unlikely to be the date when adaptive measures should be implemented. Equally so, it is quite possible that a catastrophic storm could take place before 2025 forcing that change to take place sooner rather than later. The Pathfinder scheme has attempted to highlight the issue and prepare communities to start thinking about the issue rather than assuming that the coast is always going to stay the same.

Details of the coastal pathfinder project can be found here.

The Jurassic Coast's approach to managing coastal conflict

Responsibility for protecting the Jurassic Coast ultimately lies with Natural England and the legal mechanism is through the designated Sites of Special Scientific Interest (SSSI's). The Jurassic Coast team advises Natural England directly and indirectly through the planning process and both or either teams may comment on planning applications. Furthermore, the Jurassic Coast Team are supported by a Science and Conservation Advisory Network (SCAN), a network of expert scientists who can be consulted when threats arise in order to provide the best, and most up to date science on the area in question. This network works very well for the Team but it can also help scientists as information is provided to them when opportunities present themselves, for example, landslides or storms.

In addition, there is now the Planning Policy Guidance 15: Planning and the Historic Environment (PPG15) which provides advice on the level of protection and management needed for World Heritage Sites.

It is the District Council and the Environment Agencies responsibility to protect people, property and infrastructure from coastal erosion and flooding and the funding for work comes from DEFRA who are also, ultimately responsible for the World Heritage Site status at a Government level.

There is potential for conflicting interests but the two groups work closely together in order to minimise impacts on the natural interests of the site. Both the SSSI and WHS designations were granted with many of the conflicts already in place and it has been agreed that a pragmatic approach is the best way to handle such issues. In places coast defence schemes can be maintained while minimising the impact to natural interests. In a few areas there are potentially fundamental conflicts and it is up to the planning process to balance the issues and make the decisions. The important thing on this coast is that all parties work together in a sprit of co-operation, recognising the issues rather than polarizing them.

Case studies

Lyme Regis from Black Ven. The historical development of the landslide complex has been from east to west, towards the town.Lyme Regis from Black Ven. The historical development of the landslide complex has been from east to west, towards the town.Lyme Regis is probably the best town to illustrate the conflict: the coast around the town is one of the most famous places in the world to see rocks of Lower Jurassic age while those rocks are the richest source of fossil reptiles, fish and insects from the Lower Jurassic anywhere in the world. A major reason why this particular coast is so famous is because it is subject to massive landslides that deliver huge volumes of fossils onto the beaches.

However, the evolution of the Black Ven landslide shows a migration towards Lyme Regis and now parts of the eastern edge of the town, including the main road, are considered to be at significant risk. There is a need to continue to protect the base of the cliffs from erosion and stabilise the ancient landslides above it. The old sea wall, constructed in 1953, is now showing signs of distress and could break up in an extreme storm, triggering a landslide above. Or, prolonged winter rainfall, one of the predictions for climate change, could reactivate the landslide on which part of the town is constructed

West Dorset District Council's consultant engineers recommended constructing a new sea wall in front of the old one and protecting that with rock armour. This would cover some 360 metres of the beach in engineering and extend beyond the old sea wall into the pristine World Heritage Site. The slope above was to be extensively re engineered to make it stable using a variety of methods including pilling, soil nailing and new drainage.

The old East Cliff sea wall constructed in 1957 and now showing signs of distressThe old East Cliff sea wall constructed in 1957 and now showing signs of distress The preferred scheme (indicative only, this image produced by the Jurassic Coast team)The preferred scheme (indicative only, this image produced by the Jurassic Coast team) The final scheme (indicative only, this image produced by the Jurassic Coast team)The final scheme (indicative only, this image produced by the Jurassic Coast team)

Following consultation and an expression of concern by Natural England, the World Heritage Site team and the public, regarding the extent of rock armour, the scheme was modified to a new sea wall largely constructed on the footprint of the old wall and with a more substantive foundation and no rock armour. The extent of the work on the slope was also altered to reduce the impact on the wildlife interest. The modified scheme was granted planning permission in 2011 with no objections from Natural England or the World Heritage Site team and work should start in 2013.