You need to know the costs and benefits of the following coastal management strategies:
Hard engineering – sea walls, rock armour, gabions and groynes
Soft engineering – beach nourishment and reprofiling, dune regeneration
Managed retreat – coastal realignment
Hard Engineering
Hard engineering involves use of concrete and large artificial structures by civil engineers to defend land against natural erosion processes. You need to know about four hard engineering strategies:
1. Sea Walls
A concrete wall which aims to prevent erosion of the coast by providing a barrier which reflects wave energy.
Benefits:
Very effective against coastal erosion
Reasonably long lifespan if well maintained
Can have walkways or promenades along the top for people to walk along
Costs:
Very expensive (about £5,000 per metre) and high maintenance costs
Look unnatural and ugly (not aesthetically pleasing)
May destroy habitats
2. Rock Armour
Large boulders dumped on the beach as part of the coastal defences.
Benefits:
Absorb the waves' energy, protecting the cliffs and reducing erosion
Cost only £1,000 to £3,000 per metre, which is relatively cheap compared to management strategies such as sea walls
Easy to maintain
Often used by fishermen for fishing
Costs:
Rocks are often from other parts of the coastline or from abroad. They are expensive to transport
Need regular maintenance, as rocks may be moved by storm waves
Do not fit in with the local geology
Can be very obtrusive and may make access to the beach more difficult for tourists
3. Gabions
Steel wire mesh filled with boulders used in coastal defences.
Benefits:
Relatively cheap to produce (£110 per metre) and may last for 20 to 25 years
May improve drainage of cliffs
Over time, plants will begin to grow on them, blending them into the landscape
Costs:
Cages only last 5-10 years before they rust and they need regular maintenance
For a while they look unattractive (until vegetation grows on them)
If the wire mesh breaks, they may pose a hazard to people and wildlife
4. Groynes
A wooden barrier built out into the sea to stop the longshore drift of sand and shingle, and so cause the beach to grow. It is used to build beaches to protect against cliff erosion and provide an important tourist amenity. However, by trapping sediment it deprives another area, down-drift, of new beach material.
Benefits:
Create a wider beach, which can be popular with tourists. Tourists bring in money for the local economy
Not too expensive (can cost as little as £5,000 each) and, if well maintained, may last up to 40 years
Costs:
Groynes interrupt longshore drift, starving beaches further along the coast. This often leads to increased erosion elsewhere
Timber groynes need regular maintenance to prevent them from rotting
Groynes are unnatural and may look unattractive
Soft Engineering
Soft engineering involves managing erosion by working with natural processes to help restore beaches and coastal ecosystems. You need to know about two soft engineering strategies:
1. Beach nourishment and reprofiling
Beach nourishment is the addition of new material to a beach artificially, through the dumping of large amounts of sand or shingle.
Beach reprofiling is changing the profile or shape of the beach. It usually refers to the direct transfer of material from the lower to the upper beach or, occasionally, the transfer of sand down the dune face from crest to toe.
Benefits:
Relatively cheap (compared to building a sea wall) and easy to maintain
Looks natural and blends in with the existing beach
Creates a larger beach, which may attract more tourists
Costs:
Needs constant maintenance unless structures are built to retain the beach
During re-nourishment, tourists' access to the beach will be restricted
Dredgers for beach nourishment are expensive to hire (around £300,000)
Reprofiling costs can be expensive too (often over £200,000)
2. Sand dune regeneration
Dune regeneration is action taken to build up dunes and increase vegetation to strengthen the dunes and prevent excessive coastal retreat. This includes the re-planting of marram grass to stabilise the dunes, as well as planting trees and providing boardwalks.
Benefits:
Maintains a natural coastal environment that is popular with tourists
Maintains and creates habitats for wildlife
Relatively cheap (£400 to £2,000 per 100 metres)
Costs:
Time-consuming to plant the marram grass
The dunes may need to be fenced off to prevent trampling or boardwalks may need to be built through the dunes. Fencing and boardwalks require regular maintenance
Dunes may be damaged by storms
Managed Retreat
Managed retreat involves allowing cliff erosion to occur as nature taking its course: erosion in some areas, deposition in others. Benefits include less money spent and the creation of natural environments. It may involve setting back or realigning the shoreline and allowing the sea to flood areas that were previously protected by embankments and seawalls
Coastal realignment
Benefits:
Creates a natural barrier against storm waves, reducing flood risks
Develops an intertidal habitat for wildlife and plants (salt marshes)
Nature reserves create environmental and social opportunities
Costs:
Can be expensive to set up, as relocation costs may need to be paid to landowners and homeowners