B.3.2 Coastal Erosion and Flooding Management Strategies Notes

Coastal Erosion and Sediment Supply: A Chain Reaction

What is Coastal Erosion?

1. Coastal erosion occurs when waves, currents, and tides wear away land along the coast.
2. This process is driven by natural forces like wind and water, but human activities - such as construction, deforestation, and damming rivers - can accelerate it.
3. The eroded material, often sand or sediment, is transported by water and deposited elsewhere along the coast or in marine environments.

Sediment Supply and Downstream Ecosystems

1. Sediment is essential for maintaining coastal and marine ecosystems.
2. It replenishes beaches, supports the growth of mangroves and salt marshes, and provides habitats for marine organisms.
3. When coastal erosion reduces or redirects sediment supply, it can trigger a cascade of effects downstream.

The Domino Effect on Ecosystems

When sediment supply is reduced:

1. Beaches may shrink, increasing vulnerability to storm surges and flooding.
2. Coral reefs and seagrass beds, which rely on sediment for nutrients, may degrade.
3. Mangroves and salt marshes, which act as natural barriers against coastal erosion, may fail to regenerate, further accelerating erosion.

Coastal Management Strategies Are Used to Manage Risks

1. Coastal areas face significant risks from erosion, flooding, and rising sea levels.
2. To manage these risks, a combination of engineering and adaptive strategies is used.

Cliff Line Stabilization

Hard Engineering Controls Natural Processes

1. Examples of these include:
   1. Seawalls: Tall, curved walls reflect wave energy back to the sea, protecting cliffs and land behind them.
   2. Groynes: These structures extend perpendicular to the shore, trapping sand and reducing erosion by interrupting longshore drift.
   3. Rock Armoring (Riprap): Large boulders placed at the base of cliffs absorb wave energy, reducing its impact on the coastline.

Example

Holderness Coast, UK

• Seawalls and groynes protect towns like Hornsea, but they also cause erosion further down the coast by disrupting sediment flow.

Soft Engineering: Working with Nature

1. Soft engineering strategies enhance natural defenses rather than relying on artificial structures. Examples include:
   1. Beach Nourishment: Sand is added to eroded beaches to restore their size and protect the coastline.
   2. Dune Stabilization: Planting vegetation on dunes helps anchor the sand, reducing erosion and providing a buffer against storms.

Managed Retreat: Letting Nature Take Its Course

1. Managed retreat is a coastal management strategy that involves allowing certain areas to flood or erode naturally, often to restore ecosystems like wetlands or salt marshes.
2. These natural buffers absorb wave energy, reduce flooding, and support biodiversity.

Case study

Holderness Coast, UK

1. The Holderness Coast is one of Europe’s fastest-eroding coastlines, losing up to 2 meters of land per year.
2. This erosion is driven by its soft geology (boulder clay) and powerful wave action from the North Sea.

Issues and Stakeholders

1. Local Residents: Demand hard engineering solutions like seawalls to protect homes and property.
2. Environmentalists: Advocate for managed retreat to allow natural processes and restore ecosystems.
3. Tourism Businesses: Support strategies that preserve beaches, which are vital for the local economy.

Strategies Implemented

1. Hard Engineering: Seawalls and groynes protect towns like Hornsea and Withernsea but cause erosion further down the coast.
2. Soft Engineering: Beach nourishment maintains tourist beaches but requires regular replenishment.
3. Managed Retreat: Areas like Spurn Head have been allowed to erode naturally, creating valuable habitats.

Coastal Management Strategies: Effectiveness and Trade-offs

1. Coastal management is a critical aspect of geography, particularly in the context of sustainable development.
2. It involves balancing the need to protect coastlines from natural and human-induced threats with the imperative to preserve ecosystems and support local communities.

Economic Costs: Infrastructure and Enforcement