Case Study: Coastal Environment and Management at a Local Scale (AQA A-Level Geography): Revision Notes

Case Study: Coastal Environment and Management at a Local Scale

Geographical context of Pevensey Bay

Pevensey Bay is situated on the East Sussex coastline in a low-lying zone with softer sediment deposits. It lies between harder rock types - sandstone found at Hastings to the east and chalk formations of the South Downs to the west.

The bay occupies a stretch of coastline that has been shaped by thousands of years of natural coastal processes. These processes have created and maintained a natural shingle barrier that provides important protection for the area behind it.

Key features of the area include:

• A259 coast road and railway line connecting Hastings to Portsmouth
• Nature reserves including a designated SSSI (Site of Special Scientific Interest) wetland
• Agricultural land with numerous livestock and arable farms
• Settlements including Pevensey Bay, Norman's Bay, Langley, Westham and parts of Pevensey

Physical characteristics of the coastline

The coastline at Pevensey Bay has several distinctive features:

The shingle barrier:

• Extends for 9 kilometres between Eastbourne and Bexhill
• Reaches a height of approximately 6 metres above sea level
• Projects seawards an average distance of 45 metres
• Consists of naturally deposited beach material (shingle and sand)

This shingle bank has developed over several thousand years through geomorphological processes. Whilst the barrier has been modified through coastal management today, it continues to function as a natural defence against coastal flooding.

Natural coastal processes

The shore at Pevensey Bay, like all natural coastlines, continuously adapts to reduce the impacts of wave energy. Several key processes operate along this stretch of coast:

Longshore drift is the dominant process affecting sediment movement. Beach material is transported from the south-west towards the north-east along the coastline. During major storm events, beaches become flatter as wave energy spreads the sediment, creating protective barriers that reduce wave power and prevent waves from reaching the top of the shingle bank.

Through natural processes, the shingle bank and beach have historically been maintained without human intervention. However, research has demonstrated that sediment movement is not evenly distributed - the coastline experiences irregular losses with a net loss of approximately 25,000 m³ of beach material every year.

The continuing rise in sea levels means that:

• Wave action and longshore drift continue to transport sediment in the littoral zone
• Storm frequency appears to be increasing
• The shape and position of the coastline changes almost daily
• Flood risk is the biggest concern rather than erosion, given the soft man-made defences constructed from sand and shingle

What requires protection?

The natural and man-made sea defences at Pevensey Bay currently protect substantial areas and infrastructure:

• A permanent area of 50 km² at risk of flooding - including communities in Pevensey Bay, Norman's Bay, Langley, Westham and parts of Pevensey
• 10,000 properties
• Recreational and commercial sites that support the local economy
• Transport infrastructure - the A259 coast road and railway line from Hastings to Portsmouth
• Environmental sites - nature reserves and SSSI wetland areas
• Agricultural land - numerous livestock and arable farms in the Pevensey Levels

Current coastal management approach

The management of sea defences at Pevensey Bay follows a unique organisational structure. The defences are managed and maintained through the country's first public-private partnership (PPP) for coastal management.

The Pevensey Coastal Defence Ltd (PCDL) partnership

The project was established in 2000 following a major storm event in 1997. This 1-in-20 year storm demonstrated that the shingle beach could be breached, prompting action to improve coastal defences.

Key details of the partnership:

• Established following a realisation in 1997 about breach risk
• Contract awarded to a consortium called Pevensey Coastal Defence Ltd (PCDL)
• Designed to run for 25 years
• Initial budget of $30 million

The management approach centres on working with the natural environment rather than against it. PCDL bases its management on understanding and working with the natural processes of the local sediment sub-cell. This environmentally and aesthetically acceptable approach maximises opportunities for future recreational and environmental projects.

Management philosophy

The shingle beach at Pevensey Bay extends the full length of the bay. The crest height of this defence is 6 metres, and the shingle bank extends seawards an average of 45 metres.

Traditionally, the barrier had been maintained using 150 wooden timber groynes. However, since 2000, the project has taken a different approach. As each groyne fails, it is carefully removed rather than replaced. The aim is to retain only about 10 groynes strategically positioned to maintain important discontinuities in the coastline. This creates a more open, natural beach whilst still providing effective coastal protection.

Beach management strategies

PCDL employs six main strategies to maintain the coastal defences at Pevensey Bay. Each strategy plays a specific role in managing beach sediment and maintaining effective protection.

1. Recharge
2. Recycling
3. Bypassing
4. Reprofiling
5. Groynes
6. Beach Surveys

Recharge

Beach recharge addresses the natural loss of sediment from the bay.

Longshore drift naturally removes approximately 25,000 m³ of sediment annually from the bay, transporting it towards Bexhill. Lorries then transport 5,000 m³ of this material around the harbour each year to areas further west.

To replace lost material, the remaining 20,000 m³ of gravel and sand is dredged annually from an offshore location at Sovereign Harbour. This dredged material is then pumped directly onto the beach, providing a natural source of beach material that closely matches the original composition.

Recycling

The rate of sediment movement varies from place to place along the bay. Some sections experience net accumulation of material, whilst others suffer net loss.

Following periods of particularly stormy weather - such as Winter 2013-14 - when conditions prevent the dredger from operating close to shore, recycling becomes essential. Dump trucks and bulldozers are deployed to redistribute sediment from areas of gain to areas of loss.

If relatively small amounts of sediment require recycling, a 'box' or earth scraper is attached to the bulldozer to limit the use of larger plant machinery. This reduces environmental impact and operational costs.

Bypassing

The southern arm of Sovereign Harbour creates a barrier that interrupts the natural west to east movement of sediment. Without intervention, this would cause material to accumulate on one side of the harbour.

If this accumulation were allowed to continue, sediment would eventually spill over into the harbour, blocking the lock gates. To prevent this, between 5,000 and 15,000 m³ of surplus shingle is moved from the western side of the harbour during winter months.

Reprofiling

During winter storms, destructive waves remove material from the crest of the shingle beach and deposit it lower down the beach profile. Whilst some wave energy would naturally return this material, in the meantime coastal areas may be left vulnerable to flooding.

To prevent the shingle being transported away by longshore drift before natural processes can return it, a bulldozer is used to push the material back up to reinstate the beach crest. This operation occurs during winter months when recycling is also taking place.

Groynes

Rather than maintaining the original 150 groynes along the bay, the management strategy now takes a very different approach.

Restoring all 150 groynes would have consumed 40 per cent of the 25-year budget (approximately $12 million). Instead, as each wooden groyne fails, it is carefully removed to prevent it becoming dangerous for beach users or breaking apart and floating out to sea.

The wood from removed groynes is reused - either to repair other structures or made available to local residents, businesses and farmers for recycling and reuse. Around 10 groynes are strategically retained to maintain important discontinuities in the coastline, helping create a more open, natural beach environment.

Beach surveys

Accurate monitoring enables targeted and efficient management interventions.

Twice a month, a quad bike equipped with a GPS receiver surveys the beach. The collected data produces three-dimensional models of both the shingle bank and beach. This system functions similarly to satellite navigation in a car but achieves accuracy to between 15 and 30 cm.

These regular surveys help the management team:

• Maintain the sustainability of the project
• Target replenishment activities only where needed
• Monitor how different strategies are performing
• Identify areas requiring recycling or reprofiling
• Track longer-term changes in beach morphology

Success and sustainability

The Pevensey Bay sea defences project has achieved significant recognition for its approach to coastal management.

By May 2019, the scheme had won 15 awards, including gold and silver awards under the Considerate Constructors Scheme. This scheme specifically highlights projects that try to manage the coastline sustainably, working with rather than against natural processes.

The project continues to adapt and refine its strategies, with current progress and updates available through the project website (www.pevensey-bay.co.uk).

Remember!