COASTAL MANAGEMENT

Coastal Management

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COASTAL MANAGEMENT

Only some parts of the coast are managed:
The aim of coastal management: protect homes, businesses & environment from erosion & flooding.

All coastal settlements want protection, but ££ is limited.
Choosing where is protected & how is based on a cost-benefit analysis.
££ available is usually used to protect large settlements & important industrial sites.

4 COASTAL MANAGEMENT OPTIONS:
1. HOLD THE LINE
maintaining existing defences.
2. ADVANCE THE LINE
build new defences out to sea.
3. DO NOTHING
build no coastal defences, deal with flooding/erosion as they occur.
4. RETREAT THE LINE
build no defences, move people away from the coast.

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HARD ENGINEERING: BUILT STRUCTURES

SEA WALLS

  • wall reflects waves, preventing coastal erosion.
  • acts as a barrier, preventing flooding.
  • COST: expensive to build & maintain.
  • DISADVANTAGES:
    Creates strong backwash = eroding under the wall.
    Sea Walls are unattractive.
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REVETMENTS & GABIONS

REVETMENTS

  • slanted structures built at the foot of cliffs.
  • can be made from concrete, wood or rocks.
  • waves break against them, they absorb wave energy, preventing cliff erosion.
  • COST: expensive to build, relatively cheap to maintain.
  • DISADVANTAGE: same as sea walls.

GABIONS

  • rock-filled cages.
  • wall of gabions usually built at the foot of cliffs.
  • gabions absorb wave energy, therefore reducing erosion.
  • COST: cheap.
    DISADVANTAGE: unattractive.
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RIPRAP & GROYNES

RIPRAP

  • boulders piled up along the coast that absorb energy & therefore reduce erosion.
  • COST: fairly cheap.
  • DISADVANTAGE: can shift in storms.

GROYNES

  • fences built at right angles to the coast.
  • trap beach material transported by LSD.
  • create wider beaches: slows waves by reducing energy & so provides greate protection from flooding & erosion.
  • COST: quite cheap.
  • DISADVANTAGE: starve down-drift beaches of sand.
    Thinner beaches do not protect the coast as well, leading to increased erosion & flooding.
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BREAKWATERS & EARTH BANKS

BREAKWATERS

  • usually concrete blocks/boulders deposited off the coast.
  • force waves to break offshore.
  • waves' energy & erosive power is reduced before they reach shore.
  • COST: expensive
  • DISADVANTAGE: can be damaged during storms.
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EARTH BANKS

  • mounds of earth act as flooding barrier.
  • COST: quite expensive.
  • DISADVANTAGE: can be eroded.
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TIDAL BARRIER

TIDAL BARRIER

  • tidal barriers built across river estuaries.
  • contain retractable floodgates, that can be raised to prevent flooding from storm surges.
  • COST: VERY expensive.
  • DISADVANTAGE: really, VERY expensive.
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TIDAL BARRAGE

TIDAL BARRAGE

  • dams built across river estuaries.
  • main purpose - to generate electricity.
  • water's trapped behind the dam at high tide.
  • the controlled release of water through the turbines in dam at low tide generates electricity.
  • tidal barrages also prevent flooding from storm sturges.
  • COST: VERY expensive.
  • DISADVANATAGE: barrages disrupt sediment flow, which may increase erosion elsewhere in the estuary.

e.g CARDIFF TIDAL BARRAGE - part of redevelopment scheme.

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