Coastal Environments on a Local Scale: The Coastal Proceses, Landscape and Sustainable Management of Pevensey Bay, East Sussex Flashcards
What type of land does Pevensey Bay occupy?
It occupies a low-lying area of softer sediments between standstone geology to the east at Hastings and chalk at the South Downs to the west.
What has created a natural shingle barrier?
Natural processes, sea level rise and longshore drift over the course of thousands of years.
In which direction is the longshore drift action?
From west to east.
For how long does the shingle bank extend?
It extends fro 9km between Eastbourne and Bexhill.
What has the shingle bank remained as?
It has remained as a natural defence to flooding.
Why is it difficult to manage this stretch of coastline?
The settlements need the coast to stay in the same position but it is changing everyday. Climate change is increasing sea levels and storm frequency and it is difficult to balance the costs with the needs of the residents and sustainability.
How many properties are protected by the current sea defences?
10,000
What is the size of the area that is protected from permanent flooding because of the sea defences?
50km2 and includes the area of Pevensey Bay.
What type of sites are being protected?
Commercial and recreational sites.
What road is being protected by the sea defences?
The A259 coast road is protected?
The train line from Hastings to where is being protected by current sea defences?
From Hastings to Portsmouth
What special sites are being protected by the sea defences?
Two nature reserves and a SSSI wetland site.
What type of farms are being protected by the sea defenced?
Both livestock and arable farming.
Where do the prevailing winds move beach material to?
The prevailing wind moves beach material from southwest to the northeast.
What does the prevailing wind create?
It creates beaches that are more parallel to the waves.
What happens to the beach profile during major storm events?
The beach becomes flatter which creates beach profiles that reduce wave energy thereby stopping waves from reaching the shingle bank. This therefore reduces the flood risk.
What is becoming increasingly irregular?
The movement of sediment is becoming increasingly irregular.
What is the net loss of beach each year?
The net loss of beach is 25,000m3 each year.
Which is bigger: the risk of erosion or the risk of flooding?
The risk of flooding is bigger here.
Why are soft engineering defences more effective?
They are more effective because flooding is the biggest risk and soft man-made defences that are made out of sand and shingle are more effective at breaking up and absorbing wave energy.
What is a PPP?
This is a public-private partnership and is the country’s first coastal management scheme to be organised and maintained by this.
When did the project begin?
It began in 2000.
Why did the project begin?
It began because in 1997 it was realised that there was a 1 in 20 year chance a storm event could breach the shingle beach.
Who was the contract awarded to?
It was awarded to a consortium called Pevensey Coast Defence Ltd (PDCL).
How long was the project to run for?
25 years
What was the initial budget of the scheme?
£30million
What has PDCL based its management on?
It has based it on working with the natural environment of the local sediment sub-cell.
What is the management an example of?
The management is environmentally and aesthetically acceptable and is an example of a development that maximises opportunities for future recreational and environmental projects.
What has maintained the shingle beach?
Traditionally, 150 ageing wooden timber groynes were used but since 2000 the project has removed each groyne as it fails.
How many groynes does the project hope to retain?
10
What are the 6 beach management strategies that can be seen at Pevensey Bay?
Recharge Recycling Bypassing Reprofilling Groynes Beach surveys
Explain the recharge strategy.
Lorries transport some of the beach material that has been moved by longshore drift back to the part of the beach where it was taken from, this is dredged from the sea floor just off shore and is a close match to the original sediment. Instead of using noisy bulldozers to push it into place, the material is left in situ and redistributes itself.
Explain what is meant by recycling beach material.
Dump trucks redistribute sediment from areas with a net gain to those with a net loss. This is required after storms and when conditions do not allow dredging.
What is meant by bypassing?
The southern arm of Sovereign Harbour interrupts the west to east movement of shingle causing it to accumulate. During the winter months the sediment is moved to the west, bypassing the harbour.
Why does bypassing take place in the winter?
This is so that tourism is not affected.
What is reprofiling?
Destructive waves from winter storms remove shingle from the crest of the shingle beach and deposit it lower down the beach, overtime this sediment will move back to where it originally was but until then the shingle bank is vulnerable. Therefore, a bulldozer pushes the material back up the beach to stop the shingle being transported away by longshore drift.
What would the cost of restoring the 150 groynes have been?
It would have taken 40% of the budget (around £12million).
Why are the groynes removed when they fail?
This is so that it doesn’t threaten public safety and so that it does not float out to sea. The wood is then used to repair the other groynes or given out to local residents.
What do the beach surveys entail?
Twice a month, a quad bike with a GPS receiver surveys the beach. The data is used to produce 3D models of the beach and works like a car satnav but with more accuracy (15-30mm). This ensures the sustainability of the beach and allows the areas that need replenishment, reprofiling and recycling to be targeted.
