Coasts

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  • Created by: NatalieP
  • Created on: 13-06-12 21:26

Type of wave

Constructive Waves  Long Fetch  Low energy waves Low wave height Long wave length Weak backwash Powerful swash Greater deposition Create Beaches   Destructive Waves Short fetch  High energy waves High wave height Short wave length Strong backwash Weak swash Greater erosion Shingle beaches 

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Costal Erosion

Hydraulic action- The force of the wave hitting the rock Abrasion- Pebbles and sand flung against the rock to scrape it away Attrition- Rock fragments are flung against each other wearing each other away Solution- The water dissolves the material (e.g. limestone)

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Coastlines

Concordant Coastline Lulworth Cove (Dorset) The waves attack the hard rock to widen the fault line The waves erode the soft rock creating a bay Deposition occurs which creates a beach Discordant Coastline Swanage Bay (Swanage) Waves attack the coastline The softer rock is eroded to form a bay The harder rock is left sticking out to sea and forms a headland

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Wave-cut Platform

The waves use hydraulic action and abrasion to erode the rock to create a wave-cut notch. The rock is then overhanging and weakens the cliff It then collapses as it can’t support itself This creates a wave-cut platform The cliff retreats

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Cave, Arch, Stack, Stump

The FAULTLINE is weak and very vulnerable to erosion Hydraulic action and abrasion weakens the line splitting the rock to form a CAVE Erosion will continue to happen until the cave erodes to the back of the headland which creates an ARCH The chalk of the headland is fully eroded due to hydraulic action and weathered (freeze-thaw) to create a STACK Finally the stack is further eroded and weathered to create a STUMP

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Costal Erosion Case Study

Holderness Sand-le-mir lost 26m Cliff Top Farm (Ulrome) lost farm and business Beach Café can’t sell Easington Gas Company need to be protected to avoid explosions and loss of jobs and electricity

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Coastal Transportation

Traction- Large particles (boulders) are pushed along the sea bed by the force of water Suspension- Small particles (clay) are carried along by the water Saltation- Pebble-sized rocks are bounced along the sea bed by the water Solution- Soluble materials dissolve in the water and are carried along

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Longshore Drift

The particle is moved along the beach by a wave It is taken up the beach by the swash at an angle because of the winds It is brought back to the sea by the backwash because of gravity

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Spits

As sediment is transported along the coast by longshore drift, it is deposited at a point where the coastline changes direction As the spit goes into the sea it becomes recurved as there are more low-energy waves and the wind changes direction A salt marsh is built behind the spit as there are low energy waves

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Bars

A bar is when two headlands join together Longshore drift can sometimes cause a spit to cross the bay creating a bar A lagoon is formed behind the bar When a bar connects from the shore to an island its called a tombolo

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Rising Sea Levels

Burning fossil fuels gives off CO2 This is slowly causing a climate change The air warms up therefore the sea warms up and expands (thermal expansion) OR the ice melts on the land which increases the amount of water in the oceans

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Costal Flooding Case Study

Maldives Potential to make 750,000 homeless Rising approx 3m a year Coral dies as it can’t live in deep water UK Low lying mud flats in Essex are vulnerable Norfolk broads will lose £5million a year from tourism King’s Lynn will lose agricultural land

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Costal Management

Type of defence Description Advantages Disadvantages Hard/Soft Engineering Sea Wall A large concrete wall to reflect wave energy back out to sea Protects cliffs from erosion, last along time, protects buildings and land Expensive, High maintenance cost and unsightly HARD Groynes Wooden structures in the sea to prevent longshore drift Builds up beach, protect the coastline, good for tourism Unattractive, regular maintenance HARD Rock Armour Large boulders are piled onto the beach to absorb wave energy They dissipate wave energy, protect base of cliff Unattractive, large transportation costs HARD Gabions Wire cages filled with boulders Cheap, absorb wave energy, beach can build up Unattractive, dangerous if broken HARD Concrete  Breakwater A barrier built in shallow water Absorbs waves when they break Ugly, disrupt marine life, bad for surfers/fishermen HARD Beach Nourishment Beach is built up Provides natural defence, attracts tourists, cheap Not a long-term solution SOFT Dune Regeneration Sand dunes are restored Maintains a natural coast environment, cheap Time consuming, limited access SOFT Managed retreat Areas of the coast can be flooded e.g. Farmland Encourages development of beaches, cheap People will lose land and need to compensated SOFT

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Coastal Management Case Study

Minehead Home to Butlins Resort 500,00 people a year Work on sea defences began in 1997-2001 0.6m sea wall to deflect waves Rock armour/beach nourishment/groynes A promenade has been constructed by the sea wall to make it more appealing

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Salt Marshes

Areas of periodically flooded low-lying costal wetlands Keyhaven Marshes (Hampshire) Usually found behind spits as it provides shelter for sediment accumulation. Deposition takes place as the waves are low-energy The first plants to grow are pioneer colonising plants, which help trap sediment (e.g. Cordgrass has long roots to help it stay firm) Pioneer plants help salt marshes to grow when they die as it contributes to organic matter As the mud rises the salt becomes less abundant and more complex species can be grown (e.g. Sea lavenders) The salt marsh will continue to grow until it reaches its climax of producing ash trees This is called vegetation success

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