Coastal Management Strategies and Case Study

• Sea Walls: Concrete or stone walls built at the foot of cliffs. They are often recurved (curved face) to reflect wave energy back out to sea, rather than absorbing it.
  • Pros: Highly effective at preventing flooding and often provide a paved promenade for tourists.
  • Cons: Extremely expensive (costs £5,000 to £10,000 per linear metre). Reflected waves create scouring at the base, which can undermine the wall, and they are often considered an "eyesore."
• Rock Armour (Rip-rap): Piles of large, tough boulders like granite or basalt.
  • Pros: Cheaper than sea walls (£1,000 to £3,000 per metre). The gaps between rocks allow for percolation, which successfully dissipates and absorbs wave energy.
  • Cons: Rocks are often imported from abroad (e.g., Norway to the UK), they can be slippery and dangerous for the public, and they tend to trap litter.
• Groynes: Timber or rock fence-like structures built at 90-degree angles to the coast to trap sediment moved by longshore drift.
  • Pros: Creates a wider, higher beach, which acts as a natural buffer against wave energy and boosts tourism.
  • Cons: They do not directly absorb wave energy themselves. More importantly, they cause Terminal Groyne Syndrome, starving downdrift beaches of sediment and accelerating erosion elsewhere.
• Gabions: Galvanised steel wire mesh baskets filled with rocks.
  • Pros: Very cheap (£110 to £250 per metre) and absorb wave energy well. They can be colonised by vegetation, eventually blending into the landscape.
  • Cons: They have a short lifespan (20–25 years) because the wire easily rusts or gets damaged by shingle abrasion.

Overall Effectiveness of Hard Engineering: While hard engineering strategies are undeniably effective at providing immediate, robust protection against erosion and flooding, their overall long-term effectiveness is often compromised. The astronomical financial costs of construction and maintenance, combined with severe negative environmental impacts like Terminal Groyne Syndrome, mean these strategies are rarely sustainable across a whole coastline. Ultimately, they are mostly deemed effective and justifiable only where the economic value of the protected land (such as major towns or essential infrastructure) vastly outweighs the costs.

Evaluating Soft Engineering Strategies

Can we protect the coast without pouring concrete? Soft engineering is a sustainable approach that manages the coast by working with natural processes, rather than fighting them with artificial structures.

• Beach Nourishment (Recharge): Adding sand or shingle dredged from offshore onto an existing beach.
  • Pros: Blends in perfectly with the natural appearance of the coast and creates wider beaches that heavily boost local tourism.
  • Cons: Costs around £3,000 per metre and requires constant maintenance (every 5–10 years). Dredging the sand also damages offshore marine ecosystems.
• Beach Reprofiling: Moving existing sediment from the lower beach to the upper beach using bulldozers.
  • Pros: A quick fix that looks natural and effectively builds up the beach profile against storm waves.
  • Cons: High long-term costs (e.g., Pevensey Bay spent £30m over 25 years) because it must be frequently repeated, often after every major winter storm.
• Dune Regeneration: Creating or restoring sand dunes by planting marram grass and erecting wooden fencing to trap sand.
  • Pros: Extremely cheap (£200 to £2,000 per 100 metres) and maintains local biodiversity by creating natural habitats.
  • Cons: Dunes are fragile and easily destroyed by severe storms, and the protective fences can restrict public access to the beach.

Overall Sustainability of Soft Engineering: Soft engineering represents a much more environmentally sustainable approach to coastal management because it works directly with natural processes, enhances local biodiversity, and entirely avoids starving downdrift beaches of sediment. However, its economic sustainability is often challenged by the need for continuous, long-term maintenance, as natural buffers can be easily washed away by severe winter storms. Overall, soft engineering is a highly sustainable option for preserving natural landscapes and boosting tourism, but it cannot offer the fixed, permanent defence required by dense coastal settlements.

Calculating the Viability of Coastal Management

Before any engineering strategy is approved, a Cost-Benefit Analysis (CBA) is calculated to ensure the economic benefits outweigh the costs.

Worked Example: Beach Nourishment CBA

A proposed beach nourishment scheme costs £1.5 million. It will protect 10 homes, each valued at £300,000. Is the scheme economically viable?

Step 1: Calculate the total economic benefit (value of homes protected).

• $10 \times £300{,}000 = £3{,}000{,}000$

Step 2: Calculate the Benefit-to-Cost Ratio.

• $\text{Ratio} = \frac{\text{Total Benefit}}{\text{Total Cost}}$
• $\text{Ratio} = \frac{£3{,}000{,}000}{£1{,}500{,}000}$

Step 3: State the conclusion.

• The benefit-to-cost ratio is 2:1. Because the benefits are twice as high as the costs, the scheme is economically viable.

Managed Retreat and Salt Marshes

Sometimes, the most effective way to fight the sea is to surrender to it. Managed retreat (or coastal realignment) involves deliberately breaching existing hard defences to allow low-lying coastal land to flood.

This is used as a sustainable alternative to engineering because it creates natural wave buffers and prevents coastal squeeze. When the sea floods the land, it deposits mud and silt in a low-energy environment, triggering salt marsh formation:

1. Pioneer species (like salt-tolerant cordgrass) colonise the newly formed mudflats.
2. The roots of these plants trap more sediment, gradually raising the height of the land.
3. This allows for vegetation succession, creating highly biodiverse habitats (e.g., supporting 38 bird species at Wallasea Island).

To implement this, governments must offer a compensation package to landowners. Agricultural land compensation typically ranges from £5,000 to £10,000 per hectare. However, designating an area for managed retreat causes its financial value to plummet, often leading to social conflict with residents who feel "abandoned" by local councils.

Case Study: Lyme Regis Coastal Management

Understanding coastal management requires seeing how it plays out in reality. Lyme Regis is a town on the Jurassic Coast built on unstable Blue Lias geology (permeable clay sitting over impermeable limestone), which causes massive landslides.

Reasons for Management: Erosion threatened 480 homes, the main Charmouth Road, and a vital tourism industry worth £42 million per year (supporting 880 jobs).

Strategies Used: The total scheme cost exceeded £35–£60 million across multiple phases:

• Phase 2 (£22m): Extensive beach nourishment (importing sand from France), new sea walls, stone groynes, and soil nailing (driving 19m steel nails into the cliffs to pin the clay to the limestone).
• Phase 4 (£19.5m): A 390m sea wall built at East Cliff to protect 480 homes for 50 years.
• Phase 5 (The Cobb Stabilisation): A £4.5m project to save the historic Grade I harbour. Without intervention, sea-floor erosion would cause The Cobb to fail by 2044. Strategies include a concrete toe wall and tension piles to anchor the harbour walls.

Effects and Conflicts: While homes and businesses were successfully protected, the scheme caused several conflicts. Fossil hunters were angry because stabilising the cliffs prevented new fossils from being exposed. Furthermore, the new defences interrupted longshore drift, increasing erosion rates downdrift at nearby Charmouth. Finally, some locals felt the heavy use of concrete "spoilt" the natural beauty of the area.

Case Studies: Holderness Coast and Medmerry

Protecting one stretch of coastline can sometimes guarantee the destruction of another. The Holderness Coast in Yorkshire perfectly illustrates the severe conflicts caused by hard engineering.

The Holderness Coast Conflicts: In Mappleton, £2 million was spent on two rock groynes and a rock armour revetment to protect 30 homes and the B1242 road. While successful locally, it caused Terminal Groyne Syndrome at Great Cowden. Downdrift erosion accelerated from 1m to 3.8m per year, causing local farmer Sue Earle to lose her home and livelihood. Meanwhile, at Easington, £4.5 million of rock armour was installed to protect a gas terminal handling 25% of the UK's North Sea gas, causing social resentment because nearby villages were left to erode.

Medmerry Managed Realignment (West Sussex): Maintaining Medmerry's existing shingle bank was costing £200,000 annually, and a 2008 breach had caused £5 million in damage. In 2013, a £28 million scheme deliberately breached a 110m section of the sea wall and built a new 7km embankment inland.

This created 183 hectares of new salt marsh, providing 1-in-1000-year flood protection for 348 homes. However, it caused intense conflict because three productive farms were lost, and residents felt £28 million was an excessive cost for a sparsely populated area.