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.

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.

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.

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.

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.

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.

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.