Revision for Year 11 for year 2012
2. Coasts
Y11 Geography
1
The specification for this unit
• Physical processes give rise to characteristic coastal
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landforms.
Processes: marine (wave characteristics and erosion;
longshore drift; wave deposition); sub-aerial (weathering;
mass movement).
Land forms: erosional (headlands and bays; cliffs; wave-cut
platforms; caves; arches and stacks); depositional (beaches;
spits; bars).
Role of geological structure, vegetation, people and sealevel change (estuaries and raised beaches).
Distinctive ecosystems develop along particular
stretches of coastline.
Coastal ecosystems and biodiversity (coral reefs and
mangroves).
Factors affecting the distribution of coastal ecosystems.
2
The specification for this unit
• Management of both physical processes and human
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activities is needed to sustain coastal environments.
Coastal ecosystems are of value to people, but are
threatened by tourism and other developments
(industrialisation; agricultural practices; deforestation).
Conflicts between different users of the coast and between
development and conservation.
Coasts as a natural system of interdependent places.
Coastal retreat, flooding and natural processes. Coastal
protection: soft and hard defences; management retreat.
Different views on coastal protection.
Case studies
 Case study of a located coral reef or a mangrove stand and its
management.
 Case study of a stretch of a coastline under pressure.
 Case study of one stretch of retreating coastline.
3
Marine processes
• What is the coast?
• It is a narrow zone between the land and the sea
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that is constantly changing due the effects of the
land, sea and air acting upon it.
You may recall the processes that create river
landscape are
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Erosion
Weathering
Transportation
Deposition
Mass movement
• Well you will meet them again here but there are a
few changes.
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Here they are at work
• Including the usual
suspects there is
Wave scouring waves breaking at
the base of the cliffs
swirl around the
base and result in
the removal of loose
rock
• Wave Pounding breaking down of
the cliff face due to
the sheer force of
the wave which can
exert upwards of 30
tonnes / m2 when
crashing on the
cliffs.• These are both
variations on
hydraulic action
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How is energy transferred to
create waves?
• 1. Wind creates friction on the waters surface;
• 2. Frictional drag between the wind and the waters surface causes water
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particles to rotate and energy is transferred forward;
3. When the wave reaches shallow water, it slows down due to friction
between the base of the wave and the sea bed. The shape of the wave
becomes increasingly elliptical;
4. The top of the wave continues to move forward as it is unaffected by
the friction with the sea bed. It becomes steeper and steeper and
eventually breaks;
5. Water moves up the beach as the swash;
6. Water then returns back down the beach as the backwash.
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There are two main types of
waves:
• A constructive wave is
• small in height
• has a gentle angle: there is a shallow gradient between the waves
because there is a long gap between them and each wave is not very
high
• has less energy
• has a stronger swash than backwash (material is moved up the beach by
the strong swash).
• So it is constructive because it is building the beach up – it is
constructing it
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There are two main types of
waves:
• A destructive waves is
• large in height
• has a steep angle: the is a steeper gradient between the waves because
there is a shorter gap between the waves and each wave is high
• has lots of energy
• has a weaker swash than backwash (beach is scoured and degraded as
the strong backwash pulls sand and shingle back down the beach)
• So it is destructive because it is removing material from the beach – it is
destroying it
Can you sort your
constructive waves form
your destructive ones?
Try this:
http://classtools.net/widge
ts/dustbin_0/uuQJ4.htm
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Diagrams you need to learn to draw
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
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Diagrams you need to learn to draw
Formation of a
cove e.g.
Lulworth, Dorset
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
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Diagrams you need to learn to draw
e.g.
Flanborough
Head
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
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Diagrams you need to learn to draw
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
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Diagrams you need to learn to draw
A very
useful
diagram to
explain
long shore
drift - a
MUST
LEARN
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
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Diagrams you need to learn to draw
e.g. Spurn Head
• Make sure you include types of
erosion, abrasion, hydraulic
action …..in each of these
formation diagrams
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Diagrams you need to learn to draw
e.g. Chesil Beach
• Make sure you include types of erosion, abrasion, hydraulic
action …..in each of these formation diagrams
15
This part maybe new? The role of
sea level change in coastal features?
• An estuary
• Is larger than a river
mouth, for example the
river Thames, and
resulted from a river that
flowed out into the sea
from a valley with low hills
on either side. When the
ice melted further north,
the sea level rose causing
an entry to the sea
considerably wider than its
former mouth.
This is a submergent
coastline - together with the
next 2 slides
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This part maybe new? The role of
sea level change in coastal features?
• A Ria
• During the Ice Ages, the sea level
dropped as so much ice was piled up on
the land, that there was less left in the
sea, so the UK was joined to Europe and
Alaska was joined to Russia.
• With the lower sea level, rivers that were
still flowing eroded vertically making their
flood plain at a lower level. When the ice
melted and re-entered the sea the lower
flood plains and the lower parts of the
middle course were flooded, for example
the River Tamar in Cornwall
• Where the valley was previously glaciated - scraped out by a glacier,
leaving a flat bottomed U shaped valley, then fjords is left - see picture
on page 41
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This part maybe new? The role of
sea level change in coastal features?
• Raised Beaches
• Raised beaches are another way that
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show that sea level has changed. A raised
beach is an elevated area of sloping
ground, sitting above the present tide line.
In the past this area was at sea level.
There are many examples of this feature
throughout Britain, particularly along the
West coast - this is because the area
experienced the greatest weight of ice
during the last Ice Age (about 20,000 years
ago).
During an Ice Age, the massive weight of
ice bearing down on a landmass caused it
to sink. Over time, as the earth's
temperature rose and the weight of ice
decreased, areas of land began to slowly
rise back out of the sea. This ‘bounce back'
motion - the localised change in sea level,
relative to the land - is known as isostasy,
or isostatic uplift.
• The picture of East Prawle in
South Devon shows the old cliffs
and the wave cut platform that
was created at the time the land
was lower than it is today.
This is a emergent coastline
18
The affects of geology on coasts
• Summary:
• Hard rocks give high steep cliffs, with bare
rock on the rock face and boulders and rocks
at the base
• Softer rocks give gentler, less steep cliffs - the
cliff face is smoother with evidence of
slumping (slide 17 of rivers about weathering)
with mostly sand and/or mud at the base.
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The affects of vegetation on coasts
• Summary:
• The longer the coast line has been
established, the more likely vegetation is to
be there - so not on a cliff face that is forever
changing, but yes on sand dunes and
mangrove swamps.
• But be aware that only certain plants can
withstand high salt content.
• The major impact of vegetation is that once
established, it reduces erosion
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The affects of humans on coasts
• Summary:
• 1. Settlements: coastal lowlands are very popular
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worldwide for settlement, especially protected bays
and river mouth - they make good ports
2. Where economic development is possible along
coasts, it will often happen - agriculture, industry,
fishing, tourism and increasingly energy - wind
turbines, wave and tidal power
3. Coastal management - man has sort to control
the coastline over centuries - by reducing erosion
with groynes, sea walls etc
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Beach ecosystems - coral
• Are built up entirely of tiny
living creatures, each of
which have their shells these shells form reefs.
• What do they need to
survive?
• Sea temperatures that never
go below 180C but are best
23-250C
• Light is needed for the corals
to grow, so they are in sea
less than 25 metres below
the surface, but not be
exposed to the air for too
long if at all, as they dry out
• They can only survive in sea
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water.
They need a lot of oxygen and so
need strong wave action - lots of
foamy white water.
They clear clean water, so no
sediment
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Why are corals under threat?
• Primary impacts: Very pretty areas that attract tourists, reefs
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a great source of fish, farmers attracted by fertile coastal
areas.
Secondary impacts: development of ports, blasting by
fishermen, pollution from farming, sewage all damage
pristine conditions needed by coral, deforestation leads to
silting of coastal fringe
Tertiary impacts: coral declines, fish decline, tourists move
on, local food supplies decline.
One more addition to the pot of trouble - global warming
leads to a rise in sea temperatures making it too warm for
some coral and the sea is acidifying (more CO2 absorbed
making carbonic acid) and this is damaging the delicate
shells of the coral and another cause of reef bleaching and
eventually death.
27% of coral reefs are highly threatened and another 31%
under moderate threat.
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Case study of coral reef management
- St Lucia
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Where is St Lucia?
In the Caribbean just north of Venezuela
What is the problem?
90km2 of coast was seriously threatened by human activity over fishing, tourism and coastal development, marine
pollution and sedimentation form the land
• On the West coast around
Soufriere, tourism and
urban development
resulted in conflicts of
interest - between
fishermen, divers and
yachts all wanting to use
the same areas
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Case study of coral reef management
- St Lucia
• The solution:
• The Soufriere Marine
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Management Area (SMMA)
came up with a neat solution.
They divided the coast up
into 5 different zones - see
the map.
This way, everyone can
make a living, while making
sure that enough of the coral
is protected, and they are
working hard to make sure
their ideas are sustainable
through a variety of on-going
research projects.
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Beach ecosystems - mangroves
• Most common in SE Asia most found within 30 degrees
latitude of the equator.
• They have 1 foot on the land
and one in the sea.
• The shore needs to be soft and
muddy enough for them to take
root. The shoreline needs to be
undisturbed for them to do well.
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Why are mangroves a good thing?
• They are a fish nursery, they trap silt and help
create new land, but possibly most
importantly in times of rising sea level, they
protect coastal areas in times of storm surges
that accompany tropical storms, e.g.
cyclones.
• However they have been seen as diseaseridden and are therefore being cleared in
many areas - what for? Nearly ½ are turned
into fish farming areas, another ¼ for
providing fuel and timber for construction.
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Case study of mangrove management: Bangladeshi Sunderbans
• Bangladesh are one of the few countries to
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recognize the importance of mangroves as they are
so susceptible to storm surges from cyclones and in
particular due to the majority of their land being less
than 10 metres above sea level. They also suffer
from a grave shortage of land and high population
density
As part of its Coastal Zone Policy, as mangroves
trap silt and stabilise shores, they have been
planting mangroves in the delta sediments and have
gained an extra 120 000 hectares of land as a
result. This has been helped by the Sunderbans
gaining World Heritage Status in 1998, which allows
funds to flow in to help protect the area.
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Conflict between development and conservation
• Each of the threats to the mangrove and the corals
result from conflicts between human needs and
conservation. In other words should these
ecosystems be protected or should people be
encouraged to make the fullest use of their
resources and exploit the opportunities available?
But conflicts between developers and
conservationists are not the only issues. There are
conflicts between different users or stakeholders,
householders want good housing and a clean
environment; business want space for offices,
factories; farmers want the best land kept for them;
fisherman want harbours and unpolluted sea;
tourists want hotels, beaches and amusements.
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Case study of a stretch of a coastline
under pressure.
• To manage the various pressures on the coastal
zone, the concept of ‘integrated coastal zone
management (ICZM)’ has been developed. ICZM
has the following characteristics:
 It is a long-term approach involving the sustainable and
equitable use of resources (natural, cultural, economic)
 It seeks to bring together all the various organisations
who have responsibility for managing the coastal zone
 It recognises not only the need to protect the coast but
also the importance of recreation and commerce to
coastal settlements
 It provides a framework for managing and reconciling the
various groups that have an interest in how the coastal
zone is managed
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All the sites
underlined
in red will
be saved
but not the
places in
between
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THE HOLDERNESS COASTLINE
a coastline under pressure.
• Why does it erode so rapidly?
• It erodes rapidly because the cliffs are made up of soft clay (called
‘boulder clay’) and sand. The clays and sands are unconsolidated which
means they have not been compressed and hardened. The cliffs are not
able to resist the force of the waves hitting them and frequently collapse.
The sea then removes the debris and starts to attack the cliffs again. In
this way, the cliffs recede (i.e. move inland) at a rate of around 2 metres a
year.
• Geographer’s estimate that about 7,645,000 m³ of material has been lost
from the Holdeness coast in 100 years. As the cliffs recede, villages close
to the sea are under threat and historical records show that 29 villages
have been taken by the sea since Roman times. 'Each year
approximately 1 million m³ is eroded from the Holderness coastline and
moved southwards. Only 3% of this reaches Spurn Head. The rest is
either deposited in deep offshore areas (known as 'sinks') or is carried
across or into the Humber estuary
• Around Flamborough Head, the cliffs are made up of chalk which is much
more resistant. These cliffs have not receded as far as the clay cliffs
which is why Flamborough Head forms a headland. (more detail on
management of receding coastline)
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THE HOLDERNESS COASTLINE
a coastline under pressure.
• Competing Interest Groups:
• Different interest groups may have very different views as to the most
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appropriate form of coastal defence. For example:
The Local Tourism Industry: Tourism is immensely important to this area.
It is important that the beaches are preserved but the less harsh on the
eye the coastal defence measures are, the more appealing the beaches
are likely to be to tourists.
Farmers: Some areas of the coastline are only used for farming and
spending money on defending them against the sea may not be
economically viable. Farmers are unhappy, however, to see their land
disappearing into the sea as they are not compensated for their losses.
Local Authorities: They ultimately have to pay for coastal defence. They
may not be able to afford the most effective and appropriate form of
defence. However, it is in their interests that the area should be
prosperous and one of the main forms of income is tourism, so this above
some other issues, needs protecting.
Environmental Pressure Groups/Organisations (e.g English Nature): In
the case of Spurn Head, coastal defence measures such as groynes may
have a strong negative impact on this bird sanctuary.
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THE HOLDERNESS COASTLINE
a coastline under pressure.
• Conclusion - Integrated Coastal Zone Management
• Local authorities such as in the case of Holderness, East Riding of
Yorkshire Council, have many other issues than coastal defence to
consider. These include the promotion of tourism, fisheries and farming.
• In the case of tourism, they will want to promote tourism as it is so
important to the local economy but also to maintain the environmental
quality of the coastline.
• The litter that tourists bring not only has a negative visual impact, but
may kill sea birds and dolphins, and smother rare coastal plants. Coastal
areas such as Holderness that have clean beaches and water are given
Tidy Britain Group Awards (distinctive yellow and blue Seaside Award
flags, which are awarded for clean and safe beaches by the Tidy Britain
Group) and Blue Flag awards. These are important as they demonstrate
to both visitors and tourists that the area is clean and safe but they can
be removed if the beaches and water are not kept clean.
• Integrated Coastal Zone Management looks at all of these inter-related
issues and attempts to come up with a management plan that takes all of
them into account.
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THE HOLDERNESS COASTLINE
a coastline under pressure.
• The plan:Chalk cliffs (Flamborough Head to Sewerby)
• The intent of management for this area is to allow natural processes to
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continue.
Holderness cliffs (Sewerby to Kilnsea coast)
The intent of management for this area is to allow natural processes to
continue along the frontage whilst sustaining Bridlington, Hornsea and
Withernsea as viable towns and seaside resorts. The draft policies intend
to sustain the viability of the village of Mappleton and a strategic northsouth transport link. The draft policies intend to sustain the Dimlington
and Easington gas terminals while there is a strategic need for the site.
The continued functionality of Tunstall Drain and Barmston Drain may be
maintained.
Spurn Head
The intent of management for this area is to allow the Spurn barrier to
evolve largely naturally with as limited intervention as is required to
maintain the integrity of the Spurn barrier. The intention is to maintain
access to the key facilities and assets at Spurn Point whilst causing
minimal interruption to the natural environment, coastal processes and
the functioning of Spurn Head and the Humber Estuary.
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THE HOLDERNESS COASTLINE Case
study of one stretch of retreating coastline
• As we saw on slide 33 the Holderness Coast is retreating
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very rapidly. This is partly down to the geology but there are
other issues involved too.
(a) The weather: In winter there are frequent storms which
produce stronger waves and higher sea levels. The rain also
saturates the clay cliffs and they either slump or flow.
(b) The waves attack the coastline. The dominant wind and
thus wave direction is north-east. These waves have,
therefore, a long fetch which causes very destructive waves.
The approach of the dominant waves from the north-east
causes longshore drift to move the material southwards. At
the end of this stretch of coast where it meets the Humber, is
a spit called Spurn Head. Each year it is estimated that
500,000 tonnes of material a year is moved towards the spit.
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Managing a retreating coast
• There are various strategies for defending the coastline. These can be divided
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into ‘hard engineering’ strategies (sea walls, groynes etc) and ‘soft-engineering’
strategies (beach replenishment, sand dunes etc).
HARD-ENGINEERING RESPONSES (some really useful diagrams of what
these look like on page 59)
SEA WALLS:
These are massive concrete structures which may either be straight or curved (a
'bull-nose sea wall’)
Advantages: They provide strong protection to the land immediately behind the
wall.
Disadvantages: Waves in storm conditions may break over them. They are
expensive to build and maintain.
GROYNES
These are wooden or rock structures (in which case they are called boulder
groynes) which run along the beach at right angles to the sea. They catch
sediment that is being carried along the beach by longshore drift and prevent the
removal of beach sediment downstream.
Advantages: They maintain the beach and may therefore prevent coastal erosion
of the land behind the beach.
Disadvantages: They may catch so much longshore sediment that beaches
downstream are deprived of sediment. They are unattractive to look at and so
may put tourists off visiting a beach
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Managing a retreating coast
• RIP-RAP (or ROCK ARMOUR)
• This consists of boulders placed in front of a cliff or building to protect it.
• Advantages: It is less expensive to build and maintain than sea walls. It is less
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unsightly than sea walls.
Disadvantages: It is a less formidable barrier than sea walls.
SOFT ENGINEERING RESPONSES
SAND DUNES
Sand dunes can be an effective form of defence against storm waves. They are a
very popular destination for tourists and the dunes are easily eroded by people
walking and riding bikes on them. It is important, therefore, that they are
'stabilised'. This means that there are schemes to plant grasses such as Marram
Grass, which prevent the sand from being blown away and that areas are fenced
off to protect them.
BEACH REPLENISHMENT.
This is carried on numerous beaches, the beaches at Weymouth and Lyme Regis
being but two examples. It has the benefit that it may look natural, especially if
the sediment is local but, on the other hand, replenished beaches require
constant maintenance and so this may be an expensive solution.
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Managing a retreating coast
• MANAGED RETREAT
• The final response is to do nothing. The costs of resisting the
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sea are sometimes questionable, especially if the defenses
are only protecting farmland as is the case with long
stretches of the Holderness coastline. This is, however, a
controversial response and is, understandably often resisted
by farmers.
Conclusion: Possible coastal defence measures cannot be
looked merely on the basis of whether they are suitable for
the place in question. The bigger picture must be considered.
Not only may defences such as groynes have knock-on
effects on places downstream but coastal defence is just one
of a number of issues such as tourism, waste disposal,
economic development and pollution that local authorities
have to take account of.
39
THE HOLDERNESS COASTLINE Case
study of one stretch of retreating coastline
• Various strategies have been adopted along the coastline to stop or
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slow down erosion.
Hornsea is dependent on tourism and recreation and has a small fishing
industry. Groynes have been used to protect the beach and behind that
there is a sea wall. The authorities have also used rock armour (which is
also called ‘rip rap’) to protect the esplanade behind it. The strong coastal
defences have successfully reduced coastal erosion but have increased it
to the south of the town.
Mappleton consists of only about 50 properties but suffers from a rate of
erosion of 2m a year. It needs to be defended, despite being a small
hamlet, because the B1242 is a vital road (and is only 50m from the cliff at
one point) and it would more expensive to re-route it than it is to protect
the stretch of coast between it and the sea.
In 1991 two rock groynes and a rock revetment were constructed (at a
cost of £2 million), and as a consequence a substantial beach has
accumulated. The groynes have, however, affected the movement of
material down the coastline.
The scheme has been moderately successful as the houses and the road
seem to be safe. The cliffs are however showing signs of slumping.
40
THE HOLDERNESS COASTLINE Case
study of one stretch of retreating coastline
• Skipsea
• At Skipsea, the authorities have placed cages filled with pebbles called ‘gabions’
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along the sea wall to absorb some of the wave energy.
Easington
Easington Gas Terminal is owned by British Gas and together with nearby
Dimlington Gas Terminal provides 25% of Britain’s gas.
The rate of erosion is 1 .8m a year.
The defence of Easington presented huge problems as it is so close to Spurn
Head which is a habitat for many species of bird and other fauna. The concern
was that if they had built groynes this would have prevented sediment reaching
the spit (Spurn Head) and would have increased its rate of erosion which in turn
would have threatened the bird habitats. Therefore, they built a rock revetment (at
a cost of £4.5 million) which protects the gas terminal but not the village.
Spurn Head
Despite the presence of some old groynes, the spit is no longer defended; it has
been abandoned. The neck of the spit is so narrow that winter storms were
washing over it and the spit was proving both impossible and very expensive to
defend. It will be a loss if the spit is breached. Thousands of people visit it every
year to appreciate its beauty and sense of isolation but also to bird-watch as it is
an excellent place for ornithologists to observe migrating birds in Spring and
Autumn.
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