2. Sea Walls
Building walls, can be straight or curved,
to physically stop the waves from hitting
the coast. Costs £1000-5000 per metre on
average and requires a lot of rock for the
whole area of the coastline.
An example would be
3. Advantages
Protects the base of the cliff effectively
Protects valuable property in the area
Can be used as a flood barrier to prevent extreme storm
surge damage
Absorbs the energy of waves so the coast doesn’t
Fixed line of defences allowing development up to
shoreline.
Allows amenity facilities along backshore and easy access to
beach.
4. Disadvantages
Expensive to build
Can be eroded quickly due to absorbing all the energy
Maintenance costs
Can cause beaches to dissipate as no more sediment will be deposited there
Interferes with the sediment flow along the coast
Poor design can lead to faster erosion on the wall, leading to more maintenance
costs
Provides good medium term protection, but continued erosion will cause long term
failure (30-50 year life expectancy).
Continued erosion may cause undermining and structural failure.
Complete disruption of natural beach-dune processes as the energy from waves is
directed elsewhere
5. Rock Armour
Rock armour consists of blocks of hard
resistant rock, such as granite or
limestone. These are laid at the foot
of vulnerable cliffs to add extra
protection from the sea.
Often used in conjunction with Sea
Walls
6. Advantages
Good hydraulic performance and energy dissipation.
They can also be used in exposed areas (breaks up the large amounts of
energy contained by the waves in isolated areas).
Construction costs generally cheaper than solid structures, this is because the
wire cages that are used to contain the rocks can be opened and the large
boulders easily replaced.
They also require little ongoing maintenance.
7. Disadvantages
Difficult to provide amenity value if used as primary defence (people are
unable to walk on them etc).
These often need to be made as huge wide structures, otherwise, only a
narrow area is provided for the waves to hit and be broken up.
Can be seen as an eye saw.
Not very safe for public use.
8. Gabions
Gabions are steel-wire mesh cages
(usually about 1m³ each) that hold
smaller rocks, cobbles and boulders that
both reflect and absorb wave energy. On
average, gabions cost about £1 million
per kilometre.
9. Advantages
Gabions are cheaper than revetments and sea walls.
The wire mesh improves the stability of the structure and they can be refilled
with new rocks when the old ones have been eroded.
10. Disadvantages
Gabions can cause aesthetic pollution and are prone to rusting
Gabions are also a relatively lightweight and small scale solution, which are
not as long lasting as sea walls for example
11. Revetments
A revetment is a variation of a sea wall. A revetment
is positioned at an angle to the sea, meaning that
the waves travel up the revetment. This means that
the revetment is able to dissipate wave energy. This
gives it the advantage over a sea wall, which only
shields the coast from waves.
13. Disadvantages
Revetments are very expensive to build in the first place and then to maintain
Revetments do not cope well with strong waves
Their sloped nature means that they take up more space than sea walls
Although they halt the coastline where they are built, they do not prevent
erosion in front of them
They do not support natural coastal wildlife
