Transcript CCC Revision

Coastal Change and Conflict
Revision
Revise the topic
Practice exam technique
Hard Rock Coast
Soft Rock Coast
Example
Lands End, Cornwall
Holderness coast, East
Yorkshire
Shape of
cliffs
(profile)
High, steep and rugged.
May be high but are less
rugged and not so steep.
On the
cliff face
Cliff face is often bare, with There may be piles of mud
no vegetation (plants) and
and clay which have slipped
little loose rock.
down the face of the cliff.
At the foot A few boulders and rocks
of the cliff which have fallen from the
cliff. Very few beaches.
Very few rocks, some sand
and mud.
Name
the
features.
Would
you find
them on
a hard or
soft rock
coast?
Name
the
features.
Would
you find
them on
a hard or
soft rock
coast?
Erosional
Hard rock
Erosional
Soft rock
Are they
erosional
depositional
Erosional
Hard rock
Erosional
Hard rock
Depositional
Both
Erosional
Hard rock
Depositional
Both
Depositional
Both
land form
Describe how these features formed.
You may use a diagram to help you. (4)
Joints are
small,
natural
cracks, found
in many
rocks.
Faults are
larger cracks
caused in the
past by
tectonic
movements.
Bay
Headland
(with stacks,
etc), e.g.
the Old
Harry Rocks
Discordant
coastline.
Weak areas
erode
fastest.
Bay
Concordant
coastline
Coves form here, e.g. Lulworth Cove
Name three types of erosion.
What do they do?
Wave Action
Types of Wave
Types of Erosion
Water is forced into
cracks in the rock.
This compresses the
air. When the wave
retreats the
compressed air
blasts out. This can
force the rock
apart. This is called
hydraulic action.
Loose rocks, called sediment,
are thrown against the cliff by
waves. This wears the cliff
away and chips bits of rocks off
the cliff. This is called
abrasion.
Waves crashing
against cliff
Cliff
Loose sediment knocked off
the cliff by hydraulic action
and abrasion is swirled around
by waves. It constantly
collides with other sediment,
and gradually gets worn down
into smaller, and rounded
sediment. This is called
attrition.
Longshore Drift (LSD)
Longshore Drift
Beach
Beach builds up
Sea
What features are formed by
longshore drift?
Beaches
Spits
Tombolos
Bars
Sub-aerial Processes
Weathering
Mechanical
weathering
Salt crystal growth, for example, happens because sea water contains
salt. When spray from waves lands on rocks, the water can be
evaporated leaving the salt behind. The salt crystals grow and create
stresses in the rock, causing it to break down into small fragments.
Chemical
weathering
Solution, for example, happens because all rain is slightly acidic. CO2
dissolves in water to form carbonic acid which, when rain falls on rocks,
can react with weak minerals, causing them to dissolve and the rock to
decay.
Biological
weathering
The root of vegetation, for example, can grow into cracks in a rock and
split the rock apart.
Mass Movement
Rock fall
This is one of the most sudden forms of mass movement. Rock fall
occurs when fragments of rock weathered from a cliff face fall under
gravity and collect at the base.
Slumping
This often happens when the bottom of a cliff is eroded by waves. This
makes the slope steeper and the cliff can slide downwards in a rotational
manner, often triggered by saturation due to rain, which both
‘lubricates’ the rock and makes it much heavier. You can see how the
weight added by rainwater and erosion by waves combine to cause
rotational slump.
Rotational Slumping
Saturation by rainfall
Rotational slump
Erosion by waves
Rising Sea Levels
Many scientist fear that global warming will cause sea levels to
rise. How much they will rise by is not known, but there are
estimates of between 30 cm and 100 cm by the year 2100.
• Sea level is rising today, as the sea is warming up and
expanding.
• Melting ice sheets are likely to speed up the rise.
For people who live on very low-lying land next to the sea, this
could spell trouble. There are many areas around the world at
risk:
• In Bangladesh, if sea levels rose by 100 cm, up to 15% of the
country might be flooded.
• In the UK, London and Essex are at risk, because they are
low-lying.
• Many small coral islands in the Pacific and Indian Oceans,
like the Maldives and Tuvalu could disappear underwater.
15%
100 cm
100 cm
2100
30 cm
15 cm London
Maldives
Tuvalu Bangladesh
UK
Pacific Indian
Essex
New York
Flood Risk
The New Forest Coast
An example of rapid coastal retreat and conflicting views about management
The New Forest Coast
An example of rapid coastal retreat and conflicting views about management
Highcliffe to Milford (Rapid erosion)
Hurst Spit (Erosion)
Lymington (Coastal flooding)
Value
Towns of Highcliffe, Barton on Sea and Milford on Sea built at top
of cliff
Naish Farm Holiday Village
A long shingle bank with Hurst Castle built at the end
Marshes behind the spit are of considerable wildlife
value
Valuable marsh habitats
Area of Outstanding Natural Beauty
Several Sites of Special Scientific Interest
(SSSIs)
Nature reserve
Marinas
Threats
Sand and clay cliffs are easily eroded
Rapid erosion: cliffs have retreated 60m since 1971
Mudflows and landslips happen along the cliffs after heavy rain
Towns of Barton on Sea and Milford are at risk from erosion
Spit vulnerable to erosion
Spit has been breached several times during storms
in recent years
Marshes threatened by flooding if spit is eroded or
breached
Flooding of low-lying areas such as in
1989
Water pollution; domestic sewage;
industrial waste from Esso oil refinery,
Fawley power station
Marshes threatened by flooding and
pollution
Erosion of heaches and cliffs
Management
In the past, traditional defences were used to protect cliff:
Concrete wall; groynes stop longshore drift (which moves from
west to east), and reduce effect of breaking waves by widening
beach and protect cliffs
Disadvantages: limit access to beach; eyesore; affect local
habitats; absorb wave energy, don’t deflect it; need constant
maintenance, which is expensive; can be damaged and allow
erosion to continue
Advantages: protects cliffs and towns above from erosion.
Modern, holistic management (soft engineering):
Rock revetments, stone groynes
Advantages: cost-effective; retains wildlife; enhances
environment; sustainable; allows natural processes to operate
Disadvantages: may not stop cliff erosion – loss of property, etc;
may starve Hurst Spit of sediment increasing its vulnerability to
breaching and erosion
Two options:
1 Traditional stabilisation using hard engineering
techniques, e.g. groynes
Advantages: protects spit from being breached and
protects salt marshes behind from being flooded and
altering the habitats there
Problems: stops natural processes from operating,
e.g. longshore drift; starves areas downdrift of
sediment; may increase erosion along the coast
2 Modern, holistic approach: allow spit to be
eroded and to breach
Advantages: allows natural processes to operate;
cheaper; sustainable
Disadvantages: salt marshes flooded; habitats
altered; Hurst Castle at risk from erosion at end of
spit
Groynes and coastal protetion against
cliff erosion.
Dykes and flood walls to prevent flooding
Create nature reserves to protect wildlife
habitats
Encourage sustainable tourism by making
two country parks
Conflict
Should the cliffs be allowed to erode?
Should cliffs, towns above them (e.g. Barton on sea and Milford)
be protected?
Should traditional management or more modern, holistic
approaches be used?
Should Hurst Spit be allowed to be breached (broken
through)?
Should low-lying areas (including salt marshes) be
allowed to flood?
Should natural landscapes and wildlife
habitats be protected?
Should natural landscapes be developed
for people who want to live or work
here, or for tourists?
Players
Home-owners and business owners in Highcliffe, Barton on Sea
and Milford on Sea
Tourists visiting the coast
Decision-makers in the local council
Owners of Hurst Castle, a popular tourist attraction.
Nature conservationists
Esso oil refinery
Fawley power station
Nature conservationists
Nature conservation – to
protect all areas of value
Pollution – to work with
responsible authorities to
improve water quality and
prevent pollution
Landscape – to maintain
and improve the
appearance of the coast
Coastal protection – to
research processes of
erosion and to achieve an
appropriate programme of
protection work
Recreation – to increase
enjoyment and recreational
use of the coast
New Forest
History – to conserve
features of historical and
archaeological interest
Development – to
determine criteria for
dealing with development
proposals on the coast
District Council
Coastal Management Plan
Education – to increase
public knowledge and
awareness of the coast
Economy – to recognise and
maintain the economic and
social functions of the
coast
Coastal authorities and
interest groups – to
encourage co-operation
Hard or Soft Engineering?
Sea wall
Beach nourishment
Cliff regrading
Revetments
Groynes
Rip-rap
Off-shore reefs
Managed retreat
Hard or Soft Engineering?
Sea wall
Beach nourishment
Cliff regrading
Revetments
Groynes
Rip-rap
Off-shore reefs
Managed retreat
Hard engineering methods – traditional methods using solid structures to resist forces of erosion.
Sea wall – a long
concrete barrier built at
the base of a cliff
offshore.
It is expensive to build, and the cost
of maintenance is high. It restricts
access to the beach and it may be
unsightly.
It protects the base of the cliffs
against erosion because it is made of
resistant concrete. Land and
buildings behind it are protected. If
it is ‘recurved’, it can reflect wave
energy.
Groynes – wooden, rock
or concrete ‘fences’ built
across the beach,
perpendicular to the
coastline.
They may look ugly and they do not
last very long because the wood
rots. Sand is prevented from
moving along the coast, and places
elsewhere may lose their beach and
the natural defence it provides.
These prevent the movement – by
longshore drift – of beach material
along the coast. The beach can then
build up as a natural defence against
erosion – and as an attraction for
tourists.
Rip rap – large boulders
of resistant rock.
They can be expensive. They still
let some wave energy through.
They can restrict access for the very
young and the elderly.
These absorb wave energy and
protect weak cliffs behind. They
look quite natural.
Revetments – slatted
wooden or concrete
structures built at the
base of a cliff.
Regular maintenance is needed and
they are quite expensive.
These absorb and spread wave
energy through slats. They do not
interfere with longshore drift.
Off-shore reefs – rock or
concrete barriers built on
the sea bed a short
distance from the
They are very expensive to build
and can interfere with boats.
Waves break on the barrier before
reaching the coast. These
significantly reduce wave energy and
allow a wide beach to develop.
Soft engineering methods - works with natural processes, and tries to stop erosion by stabilising
beaches and cliffs and reducing wave energy.
Beach nourishment (beach
replenishment) – adding sand
taken from somewhere else,
often offshore.
The sea keeps on eroding it
away – so it has to be replaced
every few years.
This looks completely natural.
It provides a beach for
tourists. The beach absorbs
wave energy and protects the
land or buildings behind.
Quite cheap.
Managed retreat (managed
realignment) – people and
activities are gradually moved
back from the vulnerable areas
of the coast.
Compensation has to be paid.
There is quite a lot of
disruption to people’s lives and
to businesses.
People and activities are
gradually moved back from the
vulnerable areas of coast.
Natural processes are allowed
to happen.
Cliff regrading – making the
cliff face longer, so that it is
less steep
Other methods need to be
used at the base of the cliff to
stop it being steepened again
by erosion. Properties on the
cliff may have to be
demolished.
The angle of the cliff is
reduced, making mass
movement less likely. This
method is relatively cheap.
Coastal Management
Sustainability
• Sustainable management – meeting the needs of
people now and in the future, and limiting harm to the
environment.
• Doing nothing is sustainable because no additional
resources will be needed.
• Building defences in option 1 and 2 is a lot less
sustainable because it would involve building extensive
concrete and steel defences against the sea.
• Option 3, the strategic retreat (managed realignment),
would involve some additional resources such as an
extra field for caravan sites and holiday homes, but it
would probably be less environmentally damaging that
options 1 and 2.
Exam Question
A
B
Figure 1
Study Figure 1.
a)
b)
Name the landforms labelled A and B. (1)
Describe how these landforms may have been
formed. (3)
Exam Question
(c) Using named examples, explain how
coastal management choices can cause
conflict at the coast. (5)
Describe how these landforms may have been
formed. (2)
Wave power is concentrated at the base of a
cliff, where abrasion forms a wave-cut notch.
Above this notch there is an overhang. As the
notch grows, the overhanging cliff become…
unstable and eventually collapses. The resulting
pile of rock debris at the base of the cliff….
protects the cliff from further erosion. Over
time, the loose rock is eroded by attrition,
…...… exposing the cliff to erosion again.
Using named examples, explain how coastal management
choices can cause conflict at the coast. (5)