COASTAL PROCESSES

• As the coastline is exposed to the power of the sea it tries to adapt to minimise the effects. For example waves from the southwest will move beach material northeastwards to create a beach alignement that is more parallel to the waves.
• Another example is that during a storm the beach will flatten which result in a profile that reduces the wave energy reaching the top of the beach. This change is known over the short term as coastal processes and over longer times scales as 'geomorphological change'.
• It may not be possible to provide sea defences that will survive in the longer term and the costs will increase with an increase in the water level and an increase in storms or a change in the direction of storms.

YET MORE INFORMATION ABOUT PEVENSEY SEA DEFENCES

THE PEVENSEY BAY SEA DEFENCES

• The Pevensey Bay shingle sea defences are nearly 9 km long. The crest of the sea defences lies at about 6 m A.O.D. and in most cases the shingle bank extends seawards around 45 m. The beach then becomes sand and is of a shallow gradient. There are over 150 timber groynes along the frontage, many of which are now in a relatively poor state of repair
  
• The sea defences provide protection from the permanent flooding of a 50 square km area including Pevensey Bay, Normans Bay, Langley, Westham and parts of Pevensey itself. Within this area there are more than 2000 properties, important recreational and commercial sites, transport links (main road and railway), wetlands of international importance and two important nature reserves (Hooe Flats and Pevensey Levels). Should there be a serious breach of the sea defences then all these sites could be flooded.

MORE BEACH DEFENCES!

TYPES OF DEFENCES

1) Hard Defences
Static shoreline structures such as those constructed from timber, steel, concrete, asphalt and rubble.These involve linear structures such as sea walls, revetments and breastwork and control structures of artificial headlands, offshore breastwork and groynes.
(2) Soft Defences
Mobile/ responsive defence measures which seek to work with nature rather than control it. Such structures may consist of sand or shingle beaches and dunes or banks) which may be natural or constructed, and may include control structures. These can include soft solutions of beach nourishment, cliff/dune stabilisation, bypassing and managed retreat.




TYRE STRUCTURES

• Scrap tyre constructions - a cheap, enviromentally friendly way of protecting the coastline. 100,000 scrap tyres available each year in Britain alone.
• The flexibility they offer seems tailor made in the reef's construction and environment. The fact that they are in abundance and practically free, becomes a big plus for future sea and coastal defence work.
• Scrap tyre constructions placed on the seabed offer habitat to sea life such as fish and molluscs.

PICTURES

Pevensey beach 1957

Pevensey bay 2002

Pevensey beach 1957

Pevensey Bay in 2002 (notice beach defences...)

Aerial Photographs of Pevensey Bay

map of the Pevensey Bay area

TYPE OF COASTLINE 2

• Pevensey is part of a low energy coastline. The waves heights here a relatively low. The waves spread outwards and energy is dissipated, leading to the deposition of transported material.
• Tourists are attracted to the area by the coastal features, as well as other tourist attractions such as Pevensey castle. There are establishments around Pevensey such as Pevensey hotel to accomodate tourists.

TYPE OF COASTLINE

• Pevensey bay is part of a constructive coastline. This type of coastline has constructive waves, which tend to be low waves with a long wavelength. As they approach the beach, the wave front steepens slowly, giving a gentle spill on to the beach surface. Swash rapidly loses energy as water percolates through the beach material. This has a weak backwash which can't pull sediement of the beach to impede swash from the next wave. Material is slowly moved up the beach, leading to the formation of ridges.
• The beach is part of a low energy coastline, where the wave heights are considerably low. As they approach the beach, the wave front steepens slowly, giving a gentle spill on to the beach surface. Swash rapidly loses voulume and energy as water percolates through the beach material. This has a very weak backwash which has insufficient force to pull sediment off the beach or to impede swash from the next wave. Therefore, material is slowly moved up the beach, leading to the formation of ridges.
• Many tourists are attracted to the area because of the coast and because of tourist attractions such as Pevensey castle. Places like the Pevensey bay hotel have been built to accomodate tourists.

METHODS OF PROTECTION USED FOR COAST

1) Hard Defences
Static shoreline structures such as those constructed from timber, steel, concrete, asphalt and rubble.These involve linear structures such as sea walls, revetments and breastwork and control structures of artificial headlands, offshore breastwork and groynes.
(2) Soft Defences
Mobile/ responsive defence measures which seek to work with nature rather than control it. Such structures may consist of sand or shingle beaches and dunes or banks) which may be natural or constructed, and may include control structures. These can include soft solutions of beach nourishment, cliff/dune stabilisation, bypassing and managed retreat.

DEFENCE COST ADVANTAGES AND DISADVANTAGES

Sea wall £6000 per m Very strong, but may reflect waves. Very expensive.

Rock £4500 per m Absorbs the energy of the waves, rock breaks up over time.

Revetment

Offshore £5000 per m Protects the base of the cliff. Must be large rocks.

Groynes £5000 each Will trap sand.

Beach £3500 per m Absorbs wave action. May need replacing

Nourishment

HAZARDS AND DANGERS THAT EXIST

LOSS OF INCOME

• The coastline is extremely important from a great many viewpoints. The foreshore has a large number of uses, such as sailing, bathing and fishing and is an important recreational and commercial area. There are a large number of properties both along the beach crest and immediately behind it which would be at risk of damage if further deterioration of the sea defences is not prevented.
• In the absence of improved defences, the beach will continue to erode, which in turn will reduce the strength of the sea defences. In the immediate term, the properties on the beach crest will be subject to a growing danger of subsidence and storm damage. In the medium to long term, or under particularly severe storm conditions, the greatest threat is from a breach of the sea defences. This could cause damage to several thousand properties. Grazing pastures and wildlife habitats in the Hooe Flats and Pevensey Levels would be lost and the roads and railway would be harmed and possibly closed. Some of the damage could be permanent.
• The cost of the damage from flooding would amount to several tens of millions of pounds and in past cases of breaches and flooding at other locations there has been a loss of life.

FLOOD/STORM SURGE

• The coastline of the South East is subject to huge dynamic forces and is largely the product of ongoing management for both flood defence and coastal protection reasons. Climate change is placing further pressures on this heavily managed coastline. Inundation by the sea is largely due to combinations of high tide, storm surge and wave activity but may also be associated with structural failure of defences.
• Significant stretches of our coastline and rivers are monitored each year by the Environment Agency to assist with coastal and river management decision making. There is considerable development pressure in the South East for new housing both on greenfield sites, and also on previously developed brownfield sites that are often located in floodplains. The Environment Agency seeks to discourage inappropriate development in the floodplain and to enforce compliance with Bye Laws. It will be vital to focus more strongly on Sustainable Drainage Systems (SuDS), which usetechniques to control surface water run-off as close to its origin as possible before it enters a watercourse.

Pevensey

LOCATION

Pevensey bay is located about 2 miles east of Eastbourne along the English coastline, about 3 miles south east of the old settlement of Pevensey.

TYPE Of COASTLINE

• Pevensey bay has a constructive coastline, it experiences constructive waves. They are low waves with a long wave length, usually up to 100 m. As they approach the beach, the wave front steepens slowly, giving a gentle spill onto the beach surface. Swash rapidly loses volume and energy as water percolates through the beach material. Material is slowly moved up the beach leading to the formation of ridges.
• Pevensey bay is part of a low energy coastline. Wave heights are considerably low; waves spread outwards and energy is dissipated. This leads to the deposition of transported material.
• There is much tourism associated with Pevensey bay. Tourists are attracted by the coastal location as well as many other tourist attractions in the area. Many establishments such as the Pevensey bay hotel exist in Pevensey.

METHODS OF PROTECTION USED FOR COAST

This coastline acts as an important defence against flooding and storm damage from the sea for a large area of very low-lying land immediately behind the beach. Situated in this area are a large number of properties, recreational interests, transport links, grazing pastures and two important nature reserves. These are all at risk from flooding if a breach of the defences occurs.

The sea defences of this area are the responsibility of the National Rivers Authority, Southern Region (NRA). Despite their regular maintenance efforts the sea defences are deteriorating. To restore an appropriate standard of defence the NRA are proposing to undertake major capital works. The Babtie Group, which is an engineering consultancy, has examined the coast in detail over the past two years, and have devised three options for new defences.

Option 1

The recharged shingle beach will be accomplished by pumping material from a ship on to the beach and forming it to profile using bulldozers. The beach crest will be widened substantially by about 10 metres. The material to be brought in to build up the beach will be specified after an appraisal of likely sources. This material would be selected to match the existing beach material as closely as possible. This wide beach would bury the existing beach structures which would be either extracted or cut off. Existing outfalls to the sea may need to be extended.

Option 2

For the remainder of the frontage the low groynes and rock heads of Option 1 would be replaced by large strongpoints. The purpose of these strongpoints is to contain beach material on the frontage into a series of embayments. The size of the strongpoints will be such that the beach within the embayments can reorientate itself to a stable shape under wave action. The beach within the strongpoint bays will therefore be ungroyned. The build up of material against the strongpoints will create a far greater beach area than exists at the present time and it is expected that because the beach material is contained by the strongpoints, finer material can be utilised for the beach recharge than the existing beach. This will further improve the amenity of the beach for recreational use. In the siting of the strongpoints due consideration will be given to existing sea outfalls which would be extended as necessary.

Option 3

A recharged shingle beach.
Replacement groynes to the whole frontage.
Some timber and rock breastwork.
Offshore breakwaters.

Strategy choices and their overall impacts
There are three strategies that the NRA may adopt regarding sea defences. Briefly, these are:
Do nothing: If the sea defences were effectively abandoned, the groynes would continue to deteriorate. Beach material would be lost from the frontage and some of the properties on the beach crest would be undermined and eventually lost. The beach would continue to recede until a breach occurred. Such a breach would initially flood only part of the area behind the defences but would gradually be opened up by the sea until all the levels were regularly inundated by the tide and reverted to saltmarsh.
Maintain as at present: A programme of maintenance and emergency maintenance would continue to defend the coast in the short term. However, it would not reduce the chances of a breach to an acceptable level, nor would it be able to offer an acceptable standard of sea defence against flooding for this important area. Both the risks of flooding and breaching would be increased by future anticipated sea level rises which this strategy could not accommodate.
Major capital investments: These would involve substantial improvements to the sea defences. New structures would be added to the coast and the beach would be enlarged. This is the only strategy which the NRA considers will provide appropriate long term sea defences for this area.

Cost - A £30 million scheme to give more than 3,000 homes on the Sussex coastline better protection from flooding started in April. The project will protect properties along a 9km stretch between Eastborne and Bexhill, including properties in the Pevensey Bay area.

HAZARDS AND DANGERS THAT EXIST