Aims
- Protect homes.
- Protect businesses.
- Protect the environment from erosion & flooding.
- Flooding and erosion of the coastline can have severe social, economic and environmental impacts.
- All coastal settlements want to be defended, but the amount of money availableis limited so not everywhere can be defended.
Four Options for Coastal Management
- Hold the line- maintain the existing coastal defences.
- Advance the line- build new defences.
- Do nothing- build no defences and deal with erosion and flooding as it happens.
- Managed realignment – allow the shoreline to move but manage retreat so it causes least damage.
Hard Engineering Defences – Built Structures
- Sea wall- reflects waves back out to sea, preventing erosion and flooding, expensive creates a strong backwash which erodes under the wall.
- Revetment- slanted structures built at the foot of cliffs; waves break against them which reduces their power, expensive to build and create a strong backwash.
- Gabions- rock-filled cages which absorb wave energy, cheap and ugly.
- Riprap- boulders piled up along the coast and they absorb wave energy, cheap and change shift in storms.
- Groynes- fences built at right angles to the coast which trap material transported by longshore drift, cheap and starve beaches further along.
- Breakwaters- concrete block or boulders deposited off the coast which force waves to break offshore; reducing wave power is expensive and can be damaged in storms.
- Earth bank- mounds of Earth act as a barrier to prevent flooding which are expensive and can be eroded.
- Tidal barrier- built across river estuaries; contain flood gates which are expensive.
- Tidal barrage- dams built across river estuaries; hold water at high tide and control release of it which is expensive and disrupt sediment flow which increases erosion elsewhere.
Soft Engineering Defences – Coaxing Natural Processes
- Beach nourishment- sand and shingle are added to beaches from elsewhere to create wider beaches to reduce erosion of cliffs.
- Beach stabilisation- reducing the slope angle and planting vegetation, or by sticking stakes and old tree trunks in the beach to stabilise the sand, creating wider beaches to reduce erosion.
- Dune regeneration- sand dunes are created or restored by either nourishment or stabilisation of the sand and dunes provide a barrier between land and sea, absorbing wave energy.
- Land use management- vegetation needed to stabilise the dune can easily be trampled and destroyed, leave the dune vulnerable to erosion. Wooden walkways and fenced-off areas reduce vegetation loss.
- Creating marshland- planting vegetation which stabilises the sediment which also reduces the speed of the waves, reducing their power.
- Coastal realignment- breaching an existing defence and allowing the sea to flood the land behind. Over time, it will be marshland.