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