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.
HARD ENGINEERING: BUILT STRUCTURES
- wall reflects waves, preventing coastal erosion.
- acts as a barrier, preventing flooding.
- COST: expensive to build & maintain.
Creates strong backwash = eroding under the wall.
Sea Walls are unattractive.
REVETMENTS & GABIONS
- 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.
- rock-filled cages.
- wall of gabions usually built at the foot of cliffs.
- gabions absorb wave energy, therefore reducing erosion.
- COST: cheap.
RIPRAP & GROYNES
- boulders piled up along the coast that absorb energy & therefore reduce erosion.
- COST: fairly cheap.
- DISADVANTAGE: can shift in storms.
- 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 & EARTH BANKS
- 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.
- mounds of earth act as flooding barrier.
- COST: quite expensive.
- DISADVANTAGE: can be eroded.
- 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.
- 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.