Coasts:: Coastal Management - Traditional Approaches Flashcards
Hard and soft engineering.
What is hard engineering?
Hard engineering involves the building of entirely artificial structure using various materials to reduce or stop the impact of coastal processes.
Why may different stakeholders not be happy with hard engineering along the coast?
It is an unsustainable method of management:
- expensive
- require constant maintenance
- harm the environment
What is soft engineering?
Soft engineering methods try to work with the physical and natural processes within an area to protect the coast
Describe a sea wall
A concrete barrier along the coast which absorbs the energy of the waves. Some can be curved to deflect the power of the waves.
Advantages of sea walls
- very effective
- will prevent erosion
- easily made
Disadvantages of sea walls
- deflecting waves can undermine foundations
- requires maintenance and repair
- expensive to maintain
- ugly and unnatural
Cost of sea walls
£5000 per metre
Describe groynes
Wooed fences or walls made from piles of rocks built out into the sea.
How do groynes protect the coast?
They reduce the rate of longshore drift by trapping material on one side. This extra beach then protects the coast from the sea.
Advantages of groynes
- works with natural processes
- increases tourist potential
- relatively low costs
- easily repaired
Disadvantages of groynes
- can increase erosion rates further down the coast
- unattractive
Cost of groynes
£1000 per metre
£5000-£10,000 each (200m intervals)
Lifespan of groynes
30-40 years
Lifespan of sea walls
30-50 years
Describe rip-rap
Large rocks placed at the foot of a cliff or at the top of a beach. It forms a permeable barrier to the sea, breaking up the waves but allowing some water to pass through.
Advantages of rip-rap
- easy to construct and maintain
- used for recreation e.g fishing, sunbathing
- uses natural resources
Disadvantages of rip-rap
- some erosion takes place
- can be intrusive
- looks out of place with local geology
- dangerous to climb on
Cost of rip-rap
£1000-£3000 per metre
Lifespan of rip-rap
120 years but could be removed in heavy storms
Describe revetments
Sloping wooden or concrete rock structures places at the foot of a cliff or the top of a beach. They absorb the wave’s energy and trap beach material.
Advantages of revetments
- cheap to build
- easily made
Disadvantages of revetments
- unnatural looking
- can need high levels of maintenance
- not as durable as sea wall (limited lifespan)
- doesn’t give total protection to base of cliff
Cost of revetments
£4500 per metre
Lifespan of revetments
Concrete - 30 years
Wooden - 10 years
Describe offshore breakwaters
Partly submerged rock barrier built parallel to the coast, designed to break the waves before they reach the shore, reducing wave energy.
Advantages of offshore breakwaters
- effective permeable barrier
- cheap to build
- doesn’t spoil the beach
Disadvantages of offshore breakwaters
- visually unappealing
- potential navigation hazard
- very expensive
- can be tricky to maintain
Cost of offshore breakwaters
£1.3 million for one (but depends on materials used)
Describe beach replenishment
The addition of sand or pebbles to an existing beach to make it high or wider. The sediment is usually dredged from the nearby seabed.
Advantages of beach replenishment
- looks natural and blends in with existing beach
- creates a bigger beach, increasing tourist potential
Disadvantages of beach replenishment
- needs constant maintenance because of natural processes of erosion and longshore drift
- relatively expensive
- dredger creates noise pollution, upsets tourism and kills marine life from sea bed
Cost of beach replenishment
£300,000 per 100m
Describe managed retreat
Allowing the coast to take back the land, by removing existing sea defences and allowing the land behind them to flood
Advantages of managed retreat
- marshland will form, creating habitats
- marshland will act as a natural sea defence protecting the land behind it from erosion
- cost effective
Disadvantages of managed retreat
- can cause conflict over which land should be flooded
- agricultural land is lost
- farmers or landowners need to be compensated
Example of managed retreat
Alkborough Flats, Lincolnshire
Describe cliff regrading and drainage
Reducing the angle of a cliff to stabilise it.
Drainage removes excess water to prevent landslides and slumping.
Advantages of cliff regrading and drainage
- cost effective
- very useful on clay and loose rock cliffs
Disadvantages of cliff regrading and drainage
- drains may become new lines of weakness
- dry cliffs may produce rockfalls
- effectively causes cliff to retreat, so some homes may need to be demolished
Example of cliff regrading and drainage
Mappleton, Holderness
Describe dune stabilisation
Marram grass can be planted to stabilise dunes. Areas can be fenced off to keep people off newly planted dunes.
Advantages of dune stabilisation
- maintains a natural coastal environment
- provides important wildlife habitats
- cheap and sustainable
Disadvantages of dune stabilisation
- time consuming to plant marram grass
- people may respond negatively to being kept off certain areas
- may still be eroded if people ignore signs
Cost of dune stabilisation
£200-£2000 per 100m
Example of dune stabilisation
Muir Beach, California
According to UNEP, how far from the coast do half of the world’s population live?
60km
