G23: Coastal Management

🏗️ Why Manage the Coast?

The UK uses a shoreline management plan (SMP) approach that divides the coast into cells and sub-cells, each with a management strategy. There are four possible policies for each stretch of coast:

• Hold the line: Maintain existing defences to keep the coastline in its current position
• Advance the line: Build new defences seaward of the existing coastline
• Managed retreat: Allow the coastline to retreat in a controlled way, moving defences inland
• No active intervention: Do nothing - let natural processes operate without management

🧱 Hard Engineering

Sea Walls

• Concrete or stone walls built along the coast, often with a curved face to reflect waves
• Prevent erosion and flooding by absorbing and deflecting wave energy
• Cost: £5,000-£10,000 per metre
• Advantages: Very effective at protecting the land behind; long lifespan (75-100 years)
• Disadvantages: Expensive; can cause scouring of the beach in front; ugly; restricts access to the beach

Rock Armour (Rip-Rap)

• Large boulders (1-2 tonnes each) placed at the base of cliffs or along the coast
• Boulders absorb and deflect wave energy, reducing erosion
• Cost: £1,000-£4,000 per metre
• Advantages: Cheaper than sea walls; looks more natural; allows some access; gaps between rocks absorb energy
• Disadvantages: Boulders can shift during storms; beach may lose sand; requires imported rock

Gabions

• Wire cages filled with rocks and pebbles, stacked to form walls at the cliff base
• Absorb wave energy while allowing water to drain through
• Cost: £500-£1,000 per metre
• Advantages: Relatively cheap; use local materials; allow drainage
• Disadvantages: Wire cages corrode and break after 10-15 years; look unnatural; limited effectiveness against large waves

Groynes

• Wooden, stone or concrete barriers built at right angles to the coast, extending into the sea
• Trap sediment moved by longshore drift, building up the beach on the up-drift side
• Wider beach absorbs more wave energy, protecting the cliffs behind
• Cost: £150,000-£200,000 per groyne
• Advantages: Effective at building beaches; relatively cheap; provide recreational beach
• Disadvantages: Starve the down-drift coastline of sediment, increasing erosion there; need regular maintenance; visually intrusive

🌱 Soft Engineering

Beach Nourishment

• Sand and shingle are added to an existing beach to make it wider and higher
• The wider beach absorbs more wave energy, protecting the land behind
• Material is usually dredged from offshore or imported from elsewhere
• Cost: £5-20 million per scheme
• Advantages: Looks natural; provides recreational beach; popular with tourists
• Disadvantages: Needs regular replenishment (every 5-10 years); imported sand may be different in colour/texture; can affect marine ecosystems

Dune Regeneration

• Creating or restoring sand dunes by planting marram grass and using sand fences
• Marram grass has deep roots that stabilise the sand, while its leaves trap wind-blown sand
• Boardwalks protect dunes from trampling by visitors
• Cost: £2,000-£10,000 per 100 metres
• Advantages: Natural appearance; provides habitat; low maintenance once established; absorbs wave energy
• Disadvantages: Takes time to establish; easily damaged by storms and trampling; requires space

Managed Retreat (Coastal Realignment)

• Allowing the sea to flood low-lying land in a controlled way, creating salt marsh
• Existing sea defences are deliberately breached or removed
• The new salt marsh absorbs wave energy, protecting land further inland
• Cost: £500-£5,000 per hectare
• Advantages: Creates valuable intertidal habitat; sustainable long-term; relatively cheap; natural
• Disadvantages: Farmland and property are lost; compensation is expensive; socially controversial; takes time for salt marsh to develop

📍 Case Study: The Holderness Coast

The Problem

• The coastline is made of soft boulder clay (glacial till) which erodes very easily
• Powerful destructive waves from the North Sea have a long fetch across the North Sea
• Longshore drift transports approximately 500,000 tonnes of sediment south each year
• Since Roman times, over 30 villages have been lost to the sea
• Approximately 80 properties and 28,000 m² of farmland are at risk

Management Strategies

• Hornsea: Sea wall, rock armour and groynes protect the town. The beach has been widened by groynes trapping sediment. Cost: over £5 million.
• Mappleton: Two rock groynes and a rock revetment were built in 1991 at a cost of £2 million to protect the village and the B1242 road. However, groynes trap sediment up-drift, starving the down-drift coast of material and accelerating erosion south of Mappleton.
• Withernsea: Sea wall and groynes protect the town. The sea wall was extended in the 1990s.
• Spurn Head: Managed as part of the Spurn National Nature Reserve. A policy of no active intervention applies to the spit itself, allowing natural processes to operate.
• Great Cowden/Fraisthorpe: No active intervention - farmland is being lost to erosion as there is no economic case for protecting agricultural land.

The Cost-Benefit Debate

• Protecting the entire Holderness Coast would cost billions of pounds
• The government uses cost-benefit analysis - the value of property protected must exceed the cost of defences
• Towns like Hornsea and Withernsea are protected because the value of property exceeds the cost of defences
• Farms and small settlements are not protected because the cost of defences exceeds the value of the land
• This creates winners and losers, and is socially and politically controversial

⚖️ Evaluating Coastal Management

❓ Practice Questions

✅ Answers

1. Rock armour involves placing large boulders (1-2 tonnes) at the base of cliffs (1 mark). The boulders absorb and deflect wave energy, reducing erosion of the cliff behind (1 mark).
2. Groynes are wooden or concrete barriers built at right angles to the coastline, extending into the sea (1 mark). They trap sediment being transported by longshore drift on the up-drift side (1 mark). This builds up a wider beach which absorbs more wave energy naturally (1 mark). However, groynes starve the down-drift coast of sediment, increasing erosion rates there, which is a significant disadvantage (1 mark).
3. Hard engineering uses artificial structures to resist wave energy - sea walls reflect waves and prevent flooding, but are expensive (£5,000-10,000/m) and ugly (1 mark). Rock armour and gabions absorb energy but have shorter lifespans (1 mark). Soft engineering works with natural processes - beach nourishment adds sand to create wider beaches that absorb energy naturally, looking attractive and providing recreation (1 mark). Dune regeneration uses vegetation to stabilise sand and create natural defences (1 mark). Hard engineering is generally more effective at protecting property but can cause problems down-drift (e.g., groynes starving beaches) (1 mark). Soft engineering is cheaper and more sustainable but may be less effective in extreme storms and needs ongoing maintenance (1 mark).
4. The Holderness Coast in East Yorkshire is Europe's fastest-eroding coastline, retreating at 1.8 m/year. At Hornsea, hard engineering including a sea wall, rock armour and groynes has effectively protected the town (1 mark). The groynes have built up the beach, providing recreation and protection, costing over £5 million (1 mark). However, at Mappleton, the 1991 rock groynes that protect the village have accelerated erosion down-drift at Great Cowden to 3-4 m/year by trapping sediment (1 mark). This shows hard engineering can protect one area while worsening problems elsewhere - an unsustainable approach (1 mark). Soft engineering alternatives like beach nourishment at Hornsea provide natural protection but need regular replenishment every 5-10 years (1 mark). Managed retreat is applied at Spurn Head, creating habitat but accepting land loss (1 mark). The cost-benefit approach means towns are protected while farmland is not, creating inequality (1 mark). An integrated approach combining hard and soft engineering where appropriate, with managed retreat where protection is not economically justified, would be most effective and sustainable (1 mark). However, any approach must consider the impact on neighbouring sections of coast (1 mark).

🎯 Exam Tips

• Always give both advantages AND disadvantages for each strategy
• Use the Holderness Coast as your case study - know Mappleton's down-drift impact
• For evaluation questions, consider effectiveness, cost, sustainability and environmental impact
• Explain the down-drift problem of groynes - examiners look for this specifically
• Know the difference between hard and soft engineering and be able to justify a preference
• Use cost-benefit analysis to explain why some areas are protected and others are not

📝 Exam Technique

⚠️ Common Errors

✍️ Model Answer

📊 AO Deep Dive

📝 Exam Questions by Topic

• AQA Past Papers - Topic Questions -- AQA
• Edexcel Past Papers - Topic Questions -- Edexcel
• OCR Past Papers - Topic Questions -- OCR
• Eduqas Past Papers - Topic Questions -- Eduqas
• CCEA Past Papers - Topic Questions -- CCEA

🎬 Video Resources

• BBC Bitesize
• Geography Online
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