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Canon Slade School
Geography Department
Unit 1 – Physical Geography
Q7. The Coastal Zone
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Topic Summary A: Coastal processes and landforms
B: Coastal management
Need for management coastal erosion and crumbling cliffs
threats from rising sea levels many coastal human activities
maintenance and improvement of sea defences
Hard engineering strategies sea walls groynes
rock armour
Soft engineering strategies beach nourishment dune regeneration
marsh creation
Do nothing leave to nature
allow sea to invade
Costs and benefits of these strategies Towards a more sustainable use of coastal areas
Processes at work changing the coastal zone
Weathering and mass movement
Breakdown of rocks by chemical and mechanical weathering
Mass movement of cliffs by sliding and
slumping
Deposition Factors favouring
deposition large load
sheltered water bend in coastline
Wave erosion Processes of erosion
hydraulic power abrasion attrition solution
Transportation Longshore drift Processes of transportation
traction saltation
suspension solution
Landforms of erosion appearance (description)
formation named example
Landforms of deposition appearance (description)
formation named example
How to recognise coastal landforms on OS maps
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Checklist for revision Understan
d and know
Need more revision
Do not understand
I know the difference between wave erosion, weathering and mass movement.
I can state and explain the differences between destructive and constructive waves.
I can describe how sand and shingle are transported along the coast of the UK.
I can recognise and explain the formation of cliffs, wave cut platforms, headlands, bays, caves, arches and stacks.
I can recognise and explain the formation of spits and bars.
I understand where and why beaches form.
I can give examples of hard and soft methods of engineering for coastal protection and state the differences between them.
I can explain why thermal expansion and melting land based ice cause sea levels to rise.
I know what managed retreat of the coastline means, and I understand why it is becoming preferred government policy along rural sections of coast.
Case studies
A: Cliff collapse
I know the causes (physical and human) and can give the impacts on people.
B: Coastal flooding
I know the economic, social, political and environmental impacts of flooding.
C: Coastal management
I can explain why it is needed, describe the methods used and know the costs and benefits.
D: Coastal habitat
I can describe the natural environment and strategies for conservation, allowing sustainable uses by people.
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Important coastal processes
Process Definition
Sub
aeri
al p
roce
sses
Mechanical weathering breakdown of rock without any change in its chemical composition; free–thaw is an example
Chemical weathering breakdown of rock in the place where it lies by chemical processes
Sliding (mass movement) large amounts of rock and soil move smoothly downslope
Slumping (mass movement) soil and vegetation move downslope in blocks, leaving curved scars where they have moved from
Eros
ion
proc
esse
s
Abrasion coastline eroded by waves bashing pebbles against cliffs
Hydraulic Power coastline eroded by the force of water hitting the coast
Attrition particles carried in the waves are reduced in size as they collide with one another and rock faces
Solution (erosion) chemical action on rocks by sea water dissolves rocks like chalk and limestone, making them easier to carry away
Tran
spor
t pr
oces
ses
Traction large boulders are rolled along the sea floor by the waves
Saltation small boulders are bounced along the sea floor by the waves
Suspension sand grains are carried along in the water Solution (transport) dissolved limestone rocks are carried away
in the water
Wav
es
Constructive waves (deposition) 6–9 per minute, small waves with a stronger swash
Destructive waves (erosion) 12–15 per minute, large waves with a strong backwash
Longshore drift movement of waves along the coast transporting sediment. Waves approach at an angle (swash) and retreat perpendicular to the beach (backwash).
Swash Waves moving up the beach Backwash Waves moving down the beach
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Case Studies Case Study of cliff collapse: Holderness Coast, NE England Reasons why the cliffs are vulnerable: • The cliffs are made of boulder clay. Boulder clay crumbles when it is saturated. • There are naturally narrow beaches along the coast so there is little protection for
the cliffs from the sea. • The waves that erode the Holderness coast have travelled long distances so they can
be quite powerful. • People have built groynes near places such as Mappleton. This is slowed the transport
of sediment down the coast making beaches narrower. Impacts of cliff collapse on people’s lives at Holderness: • Homes near the cliffs (e.g. in Skipsea) are at risk of collapsing into the sea. • Businesses are at risk from erosion so people will lose their jobs e.g. Seaside Caravan Park at
Ulrome is losing an average of 10 pitches a year. • Local councils will have to raise taxes in order to pay for more coastal management strategies. • Property prices along the coast have fallen sharply for those houses at risk from erosion. • Accessibility to some settlements has been affected because roads near cliff tops are at risk
of collapsing into the sea e.g. Southfield Lane which runs between Skipsea and Ulrome has been closed.
• The gas terminal at Easington is at risk (its only 25m from the cliff edge). This terminal accounts for 25% of Britain’s gas supply.
Impacts of cliff collapse on the environment: • Some sites of special scientific interest (SSSIs) are threatened e.g. The Lagoons near
Easington are separated from the sea by a bar. If the bar was eroded away, the Lagoons would be destroyed.
• 80,000 m2 of farmland is lost each year. This has a huge effect on farmer’s livelihoods.
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Hard and soft management at the coast Hard engineering – building artificial structures aimed at controlling natural processes. Strategy Description Financial
Cost Benefits Costs
Sea wall
Concrete or rock barrier placed at the foot of cliffs. Reflects the waves back into the sea.
Up to £6 million per km
Effective at stopping the sea, and often, the top can be a walkway or promenade.
Can be obtrusive and unnatural to look at. Very expensive and high maintenance costs.
Groynes Timber or rock structures that are built at right angles to the beach. They trap longshore drift and enlarge the beach.
£10,000 each (at 200m intervals).
Results in a bigger beach, which enhances tourist potential. Provides useful structures for people interested in fishing. Not too expensive.
Starves longshore drift downdrift which leads to erosion elsewhere. They are unnatural and can be obtrusive. Wood can rot too.
Rock armour
Piles of large boulders dumped at the foot of cliffs. They absorb the force of the waves.
Approx. £4,000 per metre
Relatively cheap, easy to maintain and provides interest to the coast (e.g. used for fishing)
Rocks are usually brought from other coastlines. Expensive to transport and they sometimes do not fit in with the local geology. Obtrusive.
Soft engineering – a sustainable approach to management without using artificial structures. Description Benefits Costs
Beach nourishment
Sand and shingle from elsewhere (e.g. offshore sea bed) is added to beaches
Provides wider beaches which slow waves. This gives greater protection from flooding and erosion.
Taking material from the sea bed can kills organisms like corals. It’s very expensive and it has to be repeated.
Marsh creation
Planting vegetation in mudflats/ salt marshes along the coast (usually because of managed retreat).
The vegetation stabilises the mudflats and helps reduce the speed of the waves, preventing flooding and erosion. It also creates new homes for organisms.
It isn’t useful where erosion rates are high because the marsh cannot establish itself.
Dune management
Creating or restoring sand dunes by either nourishment, or by planting vegetation to stabilise sand.
Sand dunes provide a barrier between the land and the sea. Wave energy is absorbed which prevents flooding and
The protection is limited to a small area. Very time consuming to
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erosion. Stabilisation is cheap.
plant vegetation. Nourishment is very expensive.
Managed retreat
Allowing low-lying, low- value coastal areas to be flooded by the sea. This involves removing existing sea defences.
This is a cheap option compared with maintaining expensive sea defences. Creates much- needed habitat for wildlife.
Farmers or landowners have to be compensated. Land is lost as it is flooded by the sea. Debate as to what land to let flood.
Case Study of Coastal Management: Holderness Coast, NE England Holderness is a 61km stretch of coastline. So far, only 11.4km of coastline has been protected.
PLACE EXISTING COASTAL DEFENCES
Bridlington (pop. 31,000) Fishing port and holiday resort with bathing beaches of EU quality standard.
• Sheltered naturally by Flamborough Head
• Protected from erosion and flooding by a 4.7km long sea wall as well as groynes.
Hornsea (pop. 7,500) Holiday resort with bathing beach of EU quality standard.
• Wooden groynes, and concrete sea wall. Built in early 1900s and repaired in 1980s.
Mappleton (pop. 100) Small village (on the B1242 coast road) in a farming area.
• Two rock groynes built in 1991 at a cost of £2m.
Withernsea (pop. 6,300) Holiday resort with bathing beach of EU quality standard.
• Wooden Groynes built in late 19th century.
• New sea wall with rock armour built in 1980s and replaced in 1992.
Spurn Head Sand and shingle spit with a lifeboat station, the Humber Pilots base and a nature reserve. It has Heritage Coast status.
• Rock armour and wooden groynes (now derelict) on eastern side.
• This also protects the Humber estuary behind Spurn Head.
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Case Study of Coastal Management: Managed Retreat at Wallasea Island, Essex. Wallasea Island is a low – lying coastal island formed at the confluence of the river Crouch and Roach in Essex. It was until recently used for growing wheat.
Case Study of Coastal Flooding: How will sea level rise affect the Maldives? Facts about the Maldives
The Maldives are a group of over 1000 islands made from coral (limestone) in the Indian Ocean. About 300,000 people live in the Maldives. The Maldives are the world’s lowest country. On average, each island is 1.5m above sea level. 80% of the land is below 1m. Because of rising sea levels, scientists think that the islands will be completely submerged by 2100. Social Impacts
The whole population
may have to abandon the
islands by 2100.
The sea rises up through
the permeable limestone.
This results in people’s
homes being eroded
away.
Political Impacts
The government has had
to build sea walls so that
the capital Male is
protected from flooding.
Money has been
borrowed from Japan to
pay for this.
The Maldives are
campaigning for other
countries to become
Environmental Impacts
Rising sea levels create
more destructive waves
resulting in more erosion
of the islands.
Seawater will
contaminate the
freshwater in the soil
which means that plants
will not be able to grow.
Economic Impacts
The main airport in Male
will be flooded. This will
reduce tourism in the
islands.
Coastal flooding may
damage fish processing
plants. This will affect
the Maldives main
industry.
Main features: • Cost of £7.5 million • Main aim is to replace bird habitats lost to
development. • Will also improve flood defences on the
island and reduce risk in areas such as Burnham-on- Crouch.
• New leisure opportunities will be created. • Mainly achieved through allowing the old sea
wall to be breached in July 2006. • This will allow the area to revert to a salt
marsh, providing a much needed habitat for birds.
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carbon neutral so that
the amount of carbon
dioxide emitted into the
atmosphere is reduced.
Rising sea levels mean
that there is little land
for future development
so the government is
thinking about buying
land in India and
Australia and moving
people there.
Land is being reclaimed
from the sea so that
more homes can be built.
This involves dredging
sand from the seabed
which can affect corals
and other ecosystems.
There will be less
freshwater for people so
the government will have
to build desalinisation
tanks which are
expensive.
Case Study of a coastal habitat: Keyhaven Salt Marshes, Hampshire. Vegetation Succession along Keyhaven Marshes
• Keyhaven Marsh is an area of salt marsh located behind (the lee side of) Hurst Castle Spit in
Hampshire (the south of England). • Salt marshes are areas of periodically flooded low-lying coastal wetlands that usually form in
the sheltered areas (lee) behind spits. • They are usually rich in plants, birds and animals and are very important coastal habitats.
Tidal
inlet (mudflat)
Low Marsh High Marsh Marsh uplands
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Environmental characteristics of Keyhaven Marshes • Tidal Flat - this area is mainly flooded by the sea. There is lots of deposition here of fine silt
and mud so there area is mainly a mudflat. There is very little vegetation that can grow here. However, the oystercatcher feeds here.
• Low Marsh – here, the area is flooded by the high tide. The area is periodically flooded so the
only vegetation that can grow here is cordgrass which is salt tolerant and has long roots to stabilise itself in the soil/ mud. This is a pioneer species (the first plant in the succession). The wold spider clings for hours on the cordgrass by clinging on and holding its breath for 4 – 6 hours.
• High Marsh – the soil in this area is more fertile so plants such sea lavender and sea asters
grow here. Butterflies (such as the blue butterfly) are attracted to these plants (which help pollenate other plants) and the ringed plover nests here before feeding intertidally on the mud flats. There is less salinity here in the soil due to less seawater flooding.
• Marsh Uplands – here, the soil is very fertile due to rainwater washing out excess salt and
decaying vegetation adding many nutrients to the soil. Lots of vegetation is able to grow here such as oak trees and shrubs.
Threats to the marshes: • Tourists trample the grass and disturb wildlife habitats • Decline in the number of bird species like wading birds • Dropping litter, dropping cigarettes which can cause small fires • Tourists trample the grass which can also cause erosion to the mudflats • Hurst Castle spit was breached in 1989, exposing 50-80m of the marsh to the sea.
Management Strategies and why they are sustainable
• Build boardwalks - These are raised walkways guide people across the marsh so the grass can grow below them and be protected and not get damaged.
• Fence off some of the vegetation and plant species of grass (e.g. cordgrass or marram grass) - This gives the vegetation chance to recover and the grass will stabilise the mudflats
• Information signs put up to inform visitors that Keyhaven Marshes is an important habitat - Educates tourists: shows them how to manage their waste responsibly and tourists can learn about the species and habitats, which shows them why the marsh is important.
• £5 million of Rock armour and beach nourishment in 1996 - This increased the height and
the width of the spit and has not been breached since. • Made into a SSSI (Site of Special Scientific Interest) and part of it is also a National
Nature Reserve managed by Hampshire county council - This means the species are fully monitored and managed to maintain a rich biodiversity.
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