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Coastal Erosion


[IMAGE][IMAGE]Coastal erosion presents a problem along the coastlines
of Britain. One of the many areas affected by this is
Walton-on-the-Naze, situated in the Southeast coast of England, about
sixty-five miles from London. Walton-on-the-Naze is a dated tourist
resort with a pier, which has an end shut off due to unsafe structure.
There is an area of cliffs further up coast, which are suffering from
erosion and cliff collapse. The government has erected a number of
different sea defence mechanisms including groynes, rip rap and wooden
revetments. These are erected to protect the cliffs from substantial
erosion and the eventual disappearance of Walton-on-the-Naze. Sea
defences are very expensive to set up but could have dramatic effects
on the future of Walton-on-the-Naze. There are several groups of
people who believe that it is worth the money, these include local
residents, conversationalists and local business owners. Residents
want to protect Walton because none of them wish to lose their homes
to the sea, they believe that whatever can be done to conserve their
homes should be done however high the cost. Conversationalists want to
keep the area because the Naze provides homes to a great amount of
wildlife whose homes are situated in an area most at risk from cliff
collapse. Local businesses want to protect Walton-on-the-Naze because
their livelihoods have been invested into their businesses so they are
unable to afford to lose what they have got. Some people believe that
Walton-on-the-Naze should not be saved, as there is very little which
would attract tourists and more money could be spent improving other
facilities. There are various benefits and costs from saving
Walton-on-the-Naze as the problem can only be controlled and not
prevented but is the job worth millions? "The cost of extending sea
defences at Walton-on-the-Naze are too high and the benefits are too
small." I will now investigate this hypothesis and study how true it
really is.

How is the coast of Walton being protected at present?

There are various sea defences in action along the coastline of
Walton-on-the-Naze. Some are relatively cheap but some are more
effective. Protecting a coastline is an expensive business so
understandably there are many disputes weather or not to invest in
more worthwhile defences, cheaper defences or no defences at all. With
no defences, Walton-on-the-Naze will disappear within the next hundred
years. The materials on the cliffs are eroded in the following ways;

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Wave erosion has created these low cliffs in the slide material.

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Erosion by the sea is evident at the toe of the slump beneath the
tower embayment.

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The power of the sea on concrete is shown here. It is obvious why it
can completely destruct sand and clay.

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The sea power here has moved the concrete blocks.

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At one stage, the waves had cut a sharp half-meter cliff into the
deposit, but now the whole beach has been reduced.

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Grasses have been eroded from their new deposits leaving a fine mat of
root fibres to blow in the wind.

Solutions have been given to prevent cliff erosion;

Sea Walls - A sea wall reflects the energy of a wave, as it is built
of concrete. The reflected energy creates erosion in front of the
wall; so steel pilings are used to protect the foundations. It is
approximately £7000 a meter.

Revetments - There are two types of revetment, timber and block
filled. Timber types are sloped with timber and have spaces to allow
the sea to pass through and over. As a result a beach develops behind
which protects the base of the cliff. Timber revetments are
approximately £2000 a meter and are built parallel to the coastline. A
block filled type is usually filled with rocks and acts in a similar
way to a sea wall.

Groynes - A groyne is a low wall built out into sea to slow down the
transportation of material along the coast (longshore drift). Groynes
act as barriers to allow deposition to take place, they cost between
£10000 and £30000 each.

Gabions - Steel and wire mesh baskets filled with stones and pebbles.
As the wave hits these it will break up so when it reaches the cliff,
it will be small.

Rip - Rap - Large interlocking man made boulders and rocks, which
protect the coast by breaking up the waves before they hit the cliffs.
They cost about £3500 a meter.

Bays and Headlands - If they build three large concrete groynes to act
as artificial headlands, the sea will find these impossible to erode.
The sea will continue to erode the gaps between the gaps of the
concrete groynes until two large bays are created. The water inside
the bays will be calm so the rate of erosion will get slower and
eventually stop. This method will be successful in preventing erosion
but would be financially challenging and would destroy the horizon at
Walton-on-the-Naze.

Walton-on-the-Naze has a discordant coastline so it will develop
natural bays and headlands.

Concordant coastline -

Concordant Coastline

Discordant coastline -

Discordant Coastline

The most effective of these is the sea wall but it is also very
expensive. It will last a long time because concrete is strong but
being an unnatural material, it will pollute the landscape. An
alternative idea is beach rebuilding. This only costs £3 per cubic
meter but is very easily carried by long shore drift. The sand carried
by the water will only build up further along the coast. This requires
regular replacement so I do not think it would be very effective in
the long term. Offshore breakwater protects shore from all waves by
breaking them up. This could be effective but would prove inconvenient
for boats. Gabions are not very effective because they are easily
filled up with grass and sand. Groynes and revetments are also likely
to fill up with beach material as a result of long shore drift. This
is a process in which sand is carried along the shore - line by waves
and deposited at a later stage. You can tell which way long shore
drift is by noting which side of the beach has a build up of more
sand.