PL- Coasts Flashcards
What are the two types of waves?
Constructive: Low, long wavelength, strong swash, builds up beaches.
Destructive: High, short wavelength, strong backwash, erodes beaches.
Name the four coastal erosion processes.
Hydraulic action – Water forces air into cracks.
Abrasion – Rocks thrown at cliffs.
Attrition – Rocks collide, becoming smaller.
Solution – Acidic water dissolves rocks.
What is longshore drift?
Transport of sediment along the coast by waves at an angle.
How are headlands and bays formed?
Discordant coastlines (alternating hard and soft rock).
Soft rock erodes faster, forming bays; hard rock remains, forming headlands.
How are caves, arches, stacks, and stumps formed?
Crack enlarged by hydraulic action.
Expands into a cave.
Erosion deepens it into an arch.
Arch collapses, leaving a stack.
Stack erodes, forming a stump.
What is a spit, and how does it form?
A ridge of sand extending from the coast, formed by longshore drift.
Can curve into a hook due to changing wind direction.
Salt marshes form behind.
What is a bar, and how does it form?
A ridge of sand across a bay, created by longshore drift.
Forms a lagoon behind it.
What are the types of coastal management?
Hard engineering: Sea walls, rock armour, groynes, gabions.
Soft engineering: Beach nourishment, dune regeneration.
Managed retreat: Allowing the sea to flood areas naturally.
What are the costs and benefits of managed retreat?
Benefits: Cheap, creates natural habitats.
Costs: Loss of land, relocation of communities.
Why was managed retreat chosen at Medmerry?
Reasons for managed retreat include:
* Sea wall maintenance cost £200,000 per year
* 2008 storm damage cost £5 million
* Projected sea level rise made flooding more likely
* Low-value farmland made hard engineering uneconomical
* Nearby Selsey, roads, and water treatment plant were at risk
Managed retreat is a strategy to allow certain areas to flood instead of using expensive hard engineering solutions.
What was the Medmerry managed retreat strategy?
The strategy included:
* 2013: Deliberate breach of sea wall to allow flooding
* 2 km embankment built to protect farmland, roads, and caravan parks
* Rock armour placed along embankment for protection
This approach aimed to create a natural buffer against flooding.
What were the social effects of the Medmerry scheme?
Social effects included:
* ✔️ Better protection for properties in Selsey
* ✔️ New footpaths, cycle tracks, and bridleways
* ❌ Some locals objected to loss of footpath access
The scheme aimed to enhance community access while providing flood protection.
What were the economic effects of the Medmerry scheme?
Economic effects included:
* ✔️ No more high maintenance costs for the old sea wall
* ✔️ Local landowners compensated for lost farmland
* ❌ Farmland lost, affecting farmers’ income
The compensation helped mitigate some negative impacts on local economies.
What were the environmental effects of the Medmerry scheme?
Environmental effects included:
* ✔️ Created a salt marsh, providing a natural buffer
* ✔️ Increased biodiversity, attracting waterfowl and birds
* ❌ Some people argued it was too expensive for a sparsely populated area
Salt marshes are crucial for ecosystems and act as natural defenses against flooding.
How do sea walls protect the coast?
Sea walls protect the coast by:
* Reflecting wave energy back to sea
* Acting as a direct barrier to flooding and erosion
Sea walls are a common hard engineering solution for coastal protection.
What are the advantages and disadvantages of sea walls?
Advantages and disadvantages include:
* ✔️ Very effective at preventing erosion
* ✔️ Can be used as walkways and promenades
* ❌ Expensive (£5,000-10,000 per metre)
* ❌ Can cause undercutting or wave reflection elsewhere
* ❌ Artificial appearance, unattractive
Their high cost and potential to create other issues are significant considerations.
How do groynes protect beaches?
Groynes protect beaches by:
* Trapping sediment, reducing longshore drift
* Helping maintain wider beaches for tourism
Groynes are structures built out into the water to interrupt sediment movement.
What are the pros and cons of groynes?
Pros and cons include:
* ✔️ Cheap (£150,000 per 200m)
* ✔️ Effective at building beaches, supporting tourism
* ❌ Starves beaches further along, increasing erosion
* ❌ Requires regular maintenance after storms
Their effectiveness is often localized, leading to erosion in adjacent areas.
How does rock armour (riprap) protect the coast?
Rock armour protects the coast by:
* Absorbing wave energy, reducing erosion
It consists of large boulders placed along vulnerable coastlines.
What are the advantages and disadvantages of rock armour?
Advantages and disadvantages include:
* ✔️ Cheaper than sea walls (£200,000 per 100m)
* ✔️ Quick to install and effective
* ❌ Imported rocks (often from Norway), so looks unnatural
* ❌ Can be ugly and hazardous to public
The visual impact and safety issues are important factors in planning.
What are gabions and how do they work?
Gabions are:
* Wire cages filled with rocks, placed at cliffs to prevent erosion
They are often used in temporary structures or as part of more permanent coastal defenses.
What are the pros and cons of gabions?
Pros and cons include:
* ✔️ Cheap (£50,000 per 100m)
* ✔️ Can blend in over time as plants grow over them
* ❌ Short lifespan (rusts after 10 years)
* ❌ Can break in storms, becoming ineffective
Their longevity and effectiveness can be limited by environmental conditions.
What is beach nourishment?
Beach nourishment is:
* Adding sand or pebbles to a beach to absorb wave energy
It’s a common soft engineering technique to enhance beach resilience.
