Coastal Change and Conflict Revision

Revise the topicPractice 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 no vegetation (plants) and little loose rock.

There may be piles of mud and clay which have slipped down the face of the cliff.

At the foot of the cliff

A few boulders and rocks 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?

Hard rock

Hard rock

Hard rock

Hard rock

Soft rock

Are they erosional or depositional land forms?

Both Both

Both

Erosional

Erosional

Erosional

Erosional

Depositional

Depositional Depositional

Erosional

Describe how these features formed.You may use a diagram to help you. (4)

Concordant coastline

Discordant coastline.

Bay

Headland (with stacks, etc), e.g. the Old Harry Rocks

Bay

Coves form here, e.g. Lulworth Cove

Joints are small, natural cracks, found in many rocks.

Faults are larger cracks caused in the past by tectonic movements.

Weak areas erode fastest.

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.

Cliff

Waves crashing against 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.

Beach

Sea

Wav

es

Longshore Drift

Wav

es

Beach builds up

Longshore Drift (LSD)

What features are formed by longshore drift?

Beaches

Spits

Tombolos

Bars

Sub-aerial ProcessesWeathering

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

Erosion by waves

Rotational slump

Saturation by rainfall

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 cm15 cm London Maldives Tuvalu BangladeshUK Pacific Indian Essex New York

Flood Risk

The New Forest CoastAn example of rapid coastal retreat and conflicting views about

management

The New Forest CoastAn example of rapid coastal retreat and conflicting views about

management

Highcliffe to Milford (Rapid erosion) Hurst Spit (Erosion) Lymington (Coastal flooding)

Valu

e

Towns of Highcliffe, Barton on Sea and Milford on Sea built at top of cliffNaish Farm Holiday Village

A long shingle bank with Hurst Castle built at the endMarshes behind the spit are of considerable wildlife value

Valuable marsh habitatsArea of Outstanding Natural BeautySeveral Sites of Special Scientific Interest (SSSIs)Nature reserveMarinas

Th

reats

Sand and clay cliffs are easily erodedRapid erosion: cliffs have retreated 60m since 1971Mudflows and landslips happen along the cliffs after heavy rainTowns of Barton on Sea and Milford are at risk from erosion

Spit vulnerable to erosionSpit has been breached several times during storms in recent yearsMarshes threatened by flooding if spit is eroded or breached

Flooding of low-lying areas such as in 1989Water pollution; domestic sewage; industrial waste from Esso oil refinery, Fawley power stationMarshes threatened by flooding and pollutionErosion of heaches and cliffs

Man

ag

em

en

t

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 cliffsDisadvantages: 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 continueAdvantages: protects cliffs and towns above from erosion.Modern, holistic management (soft engineering):Rock revetments, stone groynesAdvantages: cost-effective; retains wildlife; enhances environment; sustainable; allows natural processes to operateDisadvantages: 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. groynesAdvantages: protects spit from being breached and protects salt marshes behind from being flooded and altering the habitats thereProblems: stops natural processes from operating, e.g. longshore drift; starves areas downdrift of sediment; may increase erosion along the coast2 Modern, holistic approach: allow spit to be eroded and to breachAdvantages: allows natural processes to operate; cheaper; sustainableDisadvantages: 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 floodingCreate nature reserves to protect wildlife habitatsEncourage sustainable tourism by making two country parks

Con

flic

t

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?

Pla

yers

Home-owners and business owners in Highcliffe, Barton on Sea and Milford on SeaTourists visiting the coastDecision-makers in the local council

Owners of Hurst Castle, a popular tourist attraction.Nature conservationists

Esso oil refineryFawley power stationNature conservationists

Nature conservation – to protect all areas of value

Pollution – to work with responsible authorities to improve water quality and prevent pollution

Coastal protection – to research processes of erosion and to achieve an appropriate programme of protection work

Landscape – to maintain and improve the appearance of the coast

New Forest

District Council

Coastal Management Plan

Recreation – to increase enjoyment and recreational use of the coast

History – to conserve features of historical and archaeological interest

Economy – to recognise and maintain the economic and social functions of the coast

Development – to determine criteria for dealing with development proposals on the coast

Education – to increase public knowledge and awareness of the coast

Coastal authorities and interest groups – to encourage co-operation

Hard or Soft Engineering?

Sea wall

Groynes

Rip-rap

Revetments

Off-shore reefs

Cliff regrading

Managed retreat

Beach nourishment

Hard or Soft Engineering?

Sea wall

Groynes

Rip-rap

Revetments

Off-shore reefs

Cliff regrading

Managed retreat

Beach nourishment

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 coastline.

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

Study Figure 1.

a) Name the landforms labelled A and B. (1)b) Describe how these landforms may have been

formed. (3)

A

B

Figure 1

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)