pevensey bay a case study of soft engineering€¦ · pevensey bay: a case study of soft...

Pevensey Bay A case study of soft

engineering

David Redfern

All images can be found at http://www.pevensey-bay.co.uk

Pevensey Bay: a case study of soft engineering

Background (1)

• The small town of Pevensey Bay (population 4,000) is on the East Sussex coast between Eastbourne and Hastings.

• In the medieval period Pevensey Castle was on the coast to protect against invaders. Today, thanks to centuries of longshore drift and deposition, it lies 2 km inland across the saltmarsh and grazing land of the Pevensey Levels.

• The 9 km long shingle embankment, from Sovereign Harbour in the west to Bexhill in the east, protects the Levels but is no longer being replenished naturally because resorts to the west are deliberately retaining their beach material.


Background (2)

•  Every high tide the shingle is moved seawards by waves, especially in storms.

•  Without human intervention, this coast would recede to its earlier position close to the Castle.

•  Pevensey Bay, the hamlets, farms and caravan homes in the area, roads and railway all require protection.

•  The Levels is an SSSI (Site of Special Scientific Interest) and has Ramsar status as a Wetland of International Importance (an EU designation given to valuable ecosystems).


Stormy seas at Pevensey


The shingle bank

•  The shingle bank is key to the coastal defence strategy.

•  Its base lies below present-day sea level. Without the bank 50 km² of land, 10,000 properties, several caravan parks and key road and rail links would be at risk of sea flooding.

•  If the bank was not maintained and the sea breached or overtopped it, the consequences would be catastrophic. 3–4 m of floodwater could cover land behind Eastbourne and Hastings. Lives and businesses of thousands of people would be at risk.


Sovereign Harbour at different times in the late summer and autumn


The coastal defence scheme •  In 2000 the area became the first in the world to be funded by a a Public

Private Partnership/Private Finance Initiative (PPP/PFI). Four construction companies: Westminster Dredging Company, Dean and Dyball, Mackley Construction and Mouchel Parkman, created the Pevensey Bay Consortium in partnership with the Environment Agency.

•  The consortium has a 25-year contract to maintain the beach and coastal defences. This allows time to experiment with different approaches and then employ the most effective ones.

•  Local people are secure in knowing that protection is in place for their property and livelihoods until 2025. Interested stakeholders and local residents, especially those whose homes are most affected by the works, are involved in the discussion and decision-making process at all stages.


Longshore drift was limited by 150 obsolete groynes.

These were removed and not replaced, to save project costs and turn the

scheme into purely soft engineering.

In the past, shingle for beach nourishment was brought to the beaches by

lorry, along narrow roads through residential areas. Noise, dust and vehicle

fumes made residents’ lives a misery.

Removal of the groynes


Collecting shingle • Most shingle used today is brought to the beach by a flat-bottomed sea barge, the Sospan Dau. It is suitable for the gently-shelving coastline.

• The dredger scrapes shingle off the sea bed and sprays it onto the beach.

• At every high tide, 2,000 tonnes of shingle can be gathered, equivalent to 200 lorry loads per day, a big saving on environmental pollution and disruption.


Spraying shingle

• Shingle is sprayed on to the shore close to where it is needed.

• Excavators and bulldozers redistribute it on the beach.

• This provides a spectacular sight; people come to watch the operations and it has become a tourist attraction.


Bulldozers are used for beach re-profiling. After each storm, and each summer ready for the winter storms, they push the shingle back towards the beach crest. Dump trucks also move material from areas of accretion to areas of loss along the beach. Beach reprofiling


Beach surveys • Global Positioning System (GPS) surveys of the whole beach are carried out using a GPS receiver on a quad bike at low tide.

• Surveys from different times are compared and the amount of replenishment, re-profiling and recycling is targeted when and where it is most needed.

• All areas of beach frontage are protected, and work is only done when necessary.


An experimental idea? • Engineers are experimenting with using old tyres to increase the size of the shingle ridge.

• Banks of discarded tyres are laid down and covered thickly with shingle. If this works it could be used in other coastal management projects. It also reuses a waste product which is difficult to dispose of.

• As the beach is built up, new habitat is created. The East Sussex Coastal Biodiversity Project surveys plant species, numbers and distribution.

The yellow sea poppy

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