coasts Flashcards

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1
Q

describe a constructive wave

A

low wave in proportion to length

long wavelength and short fetch

strong swash

weak backwash

deposition on beach

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2
Q

describe a destructive wave

A

high wave in proportion to length

breaks downwards with great force

short wavelength and long fetch

erodes the beach making it steeper

strong backwash

weak swash

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3
Q

explain the types of coastal erosion

A

Attrition - rocks smash against each other and become smaller, rounder and smoother.

Abrasion - rocks are smashed against the cliff wearing it away.

Solution - rocks are dissolved

Hydraulic action - the power of the wave forces air and water into cracks making them bigger.

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4
Q

what does concordant mean

A

when the geology (rocks) are arranged parallel to the coastline.

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5
Q

what does discordant mean

A

when the geology (rocks) are at 90 degrees to the coastline.

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6
Q

what does fetch mean

A

the distance which the wind has blown over the sea.

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7
Q

what does geology mean

A

the different rocks and their resistance and permeability.

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8
Q

explain the process of a plunge pool

A

hard rock is not eroded. As the lower, softer layer erodes the plunge pool will develop. The harder, more resistant rock will begin to extend out or produce an overhang. The weight of this heavier, more resistant rock will eventually succumb to gravity and collapse to the plunge pool below. When this occurs the waterfall will migrate or move upstream extending the canyon and begin this process again.

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9
Q

how are bays and headlands formed

A

waves attack a section of cliff
cliff made up of different types of geology
soft rock is less resistant and therefore erodes faster retreating backwards creating a bay
hard rock is more resistant and therefore remains, forming headlands

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10
Q

what are the stages of how a stump is created

A

waves attack a cliff and a crack/crevice forms
hydraulic action causes the crack to widen and form a cave
corrasion/abrasion punches hole in back of the cave to form an arch
top of the arch is unsupported and falls to create a stack
waves weaken the bottom of the stack, it falls over forming a stump

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11
Q

describe the formation of a spit

A

longshore drift carries material along the coastline, where the coastline changes direction deposition of material takes place forming a piece of land jutting out into the sea.

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12
Q

describe the process of longshore drift

A

Waves approach the coast at an angle. Swash carries sediment up the beach at an angle. Backwash carries sediment down the beach with gravity – at right angles to the beach.

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13
Q

What are the impacts of longshore drift on the coastline?

A

can destroy a beach by removing all the material from it

can change the shape of a beach

can create landforms such as spits

can make estuaries used as harbours too shallow because of deposited material

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14
Q

What 3 factors affect the rate of landform change?

A

Geology:

Climate:

Humans:

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15
Q

For two contrasting coastlines explain the factors affecting rate of landform change

A

Holderness
Boulder clay is less resistant.
Rock groyne stopped longshore drift and narrowed the beach.
Sea wall and granite rip-rap at Withernsea to slow down erosion.
The removal of sediment offshore has made the coastline more vulnerable
Frequently subjected to powerful destructive waves from the North Sea.

Jurassic coastline
Discordant coastline created Swanage Bay and Headlands of Durlston and Ballard Point which have Old Harry’s stack.
Concordant coastline has hard limestone parallel to coastline and in one place has punched through the outer layer and created Lulworth Cove from the less resistant clays and sands.
Weight of buildings on cliff top e.g. The Grand Hotel in Swanage increase landslides.
The construction of 19 timber groynes, restoration of the sea wall, beach replenishment with 160,000 tonnes, cliff regrading - reduced rate.

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16
Q

what is cost/benefit analysis

A

weighing up the costs of protecting the coastline against the benefits of protecting the coastline

17
Q

what is rotational slumping

A

caused by water entering dry cracks in the cliff and saturates the soil so it becomes too heavy for the cliff and it slides down

18
Q

what is soil creep

A

slow downhill movement of soil

19
Q

what is weathering

A

the breakdown of rock in-situ

20
Q

what are the types of weathering

A

Physical - water gets into cracks, freezes and expands over night widening cracks or rock heated during day, expands and at night cools and contracts - layers peel off (onion skin weathering)

Biological - roots get into cracks and as plant grows, roots expand widening the cracks.

Chemical - acidic rain reacts with alkaline
rock e.g. limestone and breaks it down

21
Q

What are the different options for managing the coastline?

A
  1. Hold the line - coastline held at present place by building or maintaining defences
  2. Advance the line - build new defences to build up the coast into the sea;
  3. Retreat the line (managed retreat):- allow the coastline to retreat by not maintaining defences or punching hole in defences;
  4. Do nothing:- take no action including the maintenance or removal of defences.
22
Q

Using named examples, explain what are the social and economic reasons why some coastlines are protected and others are not?

A

Happisburgh-
Cost of defences (sea wall, rip rap and groynes) - £6m
Benefit of defences - £6m protected (Agricultural land worth £1m, 20-35 properties worth £4-7m, Grade 1 & 2 listed buildings, and a Caravan park)
Defences would reduce sediment transport along the coast.
Buy and demolish scheme would cost less than the defences.
Therefore - retreat the line (managed retreat).

Sea Palling-
Cost of defences (9 offshore reefs, 150,000 tonnes of rip rap, 1.4million m3 of sand) - £20m
Benefit of defences - £345m e.g. Norfolk Broads National Park - £18m in biodiversity, £310m in recreation and £17 million providing drinking water
Will provide protection for all assets behind beach e.g. several sites of special scientific interest and 6000ha of farmland and other settlements.
Recharge will help to supply sediment to other areas along the coast
Therefore - hold the line

23
Q

what is soft engineering examples

A

beach replenishment (where sand is placed on the beach), cliff regrading (where angle of cliff is reduced), managed retreat (where areas are allowed to flood)

24
Q

hard engineering examples

A

rip rap (large boulders placed on beach) recurved seawall (to absorb energy of waves), groynes (barriers at 90 degrees to stop longshore drift), offshore reef (causes waves to break out at sea)

25
Q

advantages of soft engineering

A

cheap,
easily available,
fewer environmental impacts

26
Q

disadvantages of soft engineering

A

Doesn’t last very long,
can be flimsy and ineffective,
uses up land (managed retreat)

27
Q

advantages of hard engineering

A

permanent, effective, reduces wave energy

28
Q

disadvantages of hard engineering

A

Expensive, ugly, needs constant maintenance

29
Q

physical factors that increase vulnerability

A

Storm surges, tropical storms etc

Narrowing of the land between Britain and Europe funnels water

Low lying areas with no coastal defences e.g. Bangladesh

Climate change and sea level rise

30
Q

How do social and economic factors increase vulnerability?

A

Areas of large % of people who have long-term health problem or disability means they will find it difficult to move.

Low levels of educational achievement means they may not be aware

Large proportion of the population who are elderly and do not want to move

Low levels of income mean they are unable to afford to move

Large population

Low income countries who do not have the ability to defend themselves

Location of key services e.g. hospitals, transport routes, water treatment plants, power plants.

31
Q

How do severe weather events and climate change increase vulnerability to coastal flooding in one named location?

A

London

Storm surges in the North Sea off the East coast of Britain being funnelled towards Thames estuary e.g. winter storms of 2013/14

If this coincides with a high tide or spring tide sea level will be even higher
Isostatic recovery - the South East is sinking by 1.5mm a year raising sea levels.

Sea levels also rising due to climate change

32
Q

How can the risk of coastal flooding be reduced?

A

Monitoring and forecasting extreme events e.g. Met Office and Environment agency

Online hazard mapping - awareness of which areas are at risk

Emergency planning - prepared with actions before, during and after can avoid loss of life

33
Q

Using named examples explain why some coastal communities are at greater risk in the future than others?

A

Maldives
Over 1000 small islands
Most of the land is no more than 1m above sea level
An increase in sea levels of up to 59cm by 2100 is predicted.
Islands are at greater risk from the effects of hurricanes
Is ranked 119th out of 228 in the world for GDP

London
Whilst London is at risk it has the £535m (£1.6 billion in today’s money) Thames Barrier completed in 1982
It protects 1.25 million people, £200 billion worth of property, tube network, historic buildings, power supplies, hospitals and schools.
It has been used just under 200 times.

34
Q

impacts of rising sea levels in a named location

A

Maldives
Most of the Maldives will be washed away in 30 years
3 of the 200 inhabited islands have already been evacuated
As sea levels rise, the coral reef habitat which forms the islands, is being destroyed - fishing yields have halved and is the second biggest industry.
Tourists will stop coming and over 90% of government income comes from tourist taxes.
The 400,000 residents will be forced to leave
Tidal surges flood homes regularly and cause salinisation preventing crops from growing.

Bangladesh
Environmental refugees, already people are migrating to Dhaka leading to overcrowding

35
Q

How are governments dealing with the problem of rising sea levels?

A

Maldives
Hulhumale reclaimed island from the sea - 2m above sea level
The capital Male has a 3m sea wall surrounding the island
Floating golf courses to enable tourism to continue
Houses being built on stilts on the highest ground
Plans to relocate the population to a new territory such as in Sri Lanka, India or Australia - environmental refugees

UK
The Thames Flood Barrier costing £535m, opened in 1982
Increasing expectation that individuals and communities should help themselves to prepare