Coastal Environments Flashcards

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1
Q

What are waves caused by?

A

Winds blowing over sea.

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2
Q

How is the power of the waves determined by?

A
  1. Stronger wind, bigger waves.
  2. Length of time wind blows.
  3. Fetch.
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3
Q

What is the fetch?

A

Greater distance of open water, larger waves.
E.g. contrast east and west of Ireland, Atlantic and Irish Sea.

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4
Q

How do waves form?

A

As wave approaches shallow water near coastline, friction caused by seabed slows lower section of wave more than upper section.
Upper section of wave reaches crest then topples over (breaks) and either hits cliff face or surges up beach as swath of wave.
As wave retreats, creates backwash.
Waves with strong swans and weak backwash called constructive waves as push material up beach.
Waves with strong backwash pull material out to sea, destructive waves erode coasts.

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5
Q

What are the characteristics of destructive waves?

A
  1. Strong backwash compared to swash.
  2. High in relation to length.
  3. Form frequently (break at rate around 15 per min).
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6
Q

What are the characteristics of constructive waves?

A
  1. Weak backwash compared to swash.
  2. Long in relation to height.
  3. Are gentle ( break at rate 6-9 per min).
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7
Q

What are the 4 processes of coastal erosion?

A

Corrasion, attrition, solution and hydraulic action.

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8
Q

How does corrasion erode a coastline?

A

When wave hits coast, throws pebbles and sand against cliff face.
Knock off small parts of cliff and cause undercutting.
Also known as abrasion.

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9
Q

How does attrition erode a coastline?

A

Particles transported by sea hit against one another, reducing size and making them more rounded, like in rivers.

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10
Q

How does solution erode a coastline?

A

Seawater dissolve away rocks from seabed or cliffs.
Process especially effective on limestone coasts and can create spectacular caves.
Also known as corrosion.

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11
Q

How does hydraulic action erode a coastline?

A

Power of sea can physically wash away soft rocks like boulder clay.
Under storm conditions with strong waves, hundreds of tonnes seawater hit coast.
Also, air can be trapped in small cracks within cliff when wave breaks against it.
Compressed air widens cracks, leading to sections of cliff breaking away from main cliff face.

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12
Q

What are the 4 processes of transportation along a coastline?

A

Solution, suspension, saltation, traction.

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13
Q

How does solution transport particles along a coastline?

A

Minerals dissolved in seawater and carried in solution.
Load not visible.
Load can come from cliffs made of chalk or limestone, and calcium carbonate carried along in solution.

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14
Q

How does suspension transport particles along a coastline?

A

Small particles carried in water (e.g. silts and clays), can make water look cloudy.
Currents pick up large amounts of sediment in suspension during storms, when strong winds generate high energy waves.

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15
Q

How does saltation transport particles along a coastline?

A

Load bounced along seabed (e.g. small pieces shingle or large sand grains).
Currents cannot keep larger and heavier sediment afloat for long periods.

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16
Q

How does traction transport particles along a coastline?

A

Pebbles and larger sediment rolled along seabed.

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17
Q

How does the sea transport material?

A

Longshore drift occurs when waves hit beach at angle.
Swash moves up beach at angle, but backwash draws down straight.
Over time, material transported along coast.

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18
Q

How does the sea deposit material?

A

When load of seas and oceans builds up on coastline it forms beaches, spits and sand dunes.
Material added by constructive waves.
Occurs during periods of light winds.
Summer most common period for deposition in UK.
Constructive waves most effective in sheltered coastal locations such as bays.

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19
Q

How do headlands form?

A

Stretches of coastline do not erode evenly.
Sections of cliff made from hard resistant rock resist hydraulic action and corrosive power of sea.
They stick out forming headlands.
Face full force of destructive waves and often located at coastal landforms created by erosion, such as caves, arches and stacks.

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20
Q

What are bays like?

A

Crescent-shaped indents between two headlands, made from soft rock (e.g. clay or sandstone), erode easily.
Water is shallow and calm as sheltered, enables sand to be deposited, forming beaches.

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21
Q

What is a cliff?

A

Vertical rock face along coast.
Shape determined by nature of its geology.
Those of rock cliff made of determines how resistant it is to erosion, and way layers (strata) of rock are angled can determine shape of stiff.

22
Q

What is a wave cut platform?

A

Narrow flat area often seen at base of cliff.
Caused by erosion.

23
Q

How do wave cut platforms form?

A
  1. Notch formed at base of cliff due to corrasion and hydraulic action, becomes point of weakness.
  2. Upper cliff face undercut and collapses.
  3. Happens again and again, until wave cut platform created at base of cliff.
  4. Only fully exposed at low tide.
24
Q

How do caves, arches and stacks form?

A
  1. Wave cut notch may enlarge into a cave.
  2. Following further erosion, cave erodes through headland by hydraulic action and corrasion to form arch.
  3. Waves and weathering from elements undermine upper portion of arch until cannot hold own weight, collapses to leave stack.
25
Q

How do stumps form?

A

Headland retreats and stack eroded until becomes stump.

26
Q

How are beaches formed?

A

Most familiar coastal land form created by deposition.
Formed in intertidal area between high and low tide where constructive waves push material (e.g. sand, shingle and pebbles) on to coast.p

27
Q

What are spits?

A

Depositional features made of sand that look like beaches and extend out from mainland into sea.

28
Q

What conditions need to be met for a spit to form?

A
  1. Constant supply of sand or other material from erosion further up coast.
  2. Longshore drift operates most of time.
  3. Coastline has sudden change in direction to leave sheltered Bay Area.
  4. Sea is quite shallow.
29
Q

How do spits form?

A

Occur because waves hit shore at angle, moving material along beach due to Longshore drift.
When material reaches natural break in coastline, sand continues on and can build up, breaking through surface and forming spit attached to headland.
Spits become established if occur at estuary, as silt and mud from river deposited behind spit, making new land.
If angle of waves changes as spit extends into estuary, tip may become hooked.

30
Q

What does sustainability mean in geography?

A

Environmentally friendly strategies which work with environment rather than against it.
Also means to fulfil needs of present without compromising ability of future generations to meet their own needs.

31
Q

What are human uses at coastlines?

A
  1. Marsh areas provide natural areas for waste assimilation and detoxification.
  2. Economically through main ports which are centre of commerce, trade and investment.
  3. Area used to inhabit people.
  4. Fishing which can be vital for generating income.
  5. Tourism to help attract people through beaches.
  6. Suitable for construction of harbours, ports and cities for trade.
32
Q

What is hard engineering for coastlines?

A

Building artificial structures along coastline to reduce erosion or manage deposition.

33
Q

How do sea walls manage coastlines?

A

Look like tall concrete walls built at back of beaches.
May have curved shape designed to deflect erosion energy of wave and add extra protection against waves topping wall.

34
Q

How sustainable are sea walls at managing coastline?

A

Expensive to build (cost around £10 million per km), and need for constant maintenance means costs continue.
Can be economically acceptable if needed to protect many people and properties, e.g. Portrush.

35
Q

How do groynes manage coastlines?

A

Used to ensure survival of a beach from Longshore drift displacing sand from beach.
Often made out of hard wood and look like low fences along beach at 50m intervals.
Slow Longshore drift and promote disposition of sand, building up beach.

36
Q

How sustainable are groynes at managing a coastline?

A

Maintain tourist attraction to coastal area, resorts keen to conserve beaches for income.
Have lifespan of 20 years so need to be replaced.
Cost around £5,000 per m to build.
Oder construction techniques favour rock groynes, have much longer lifespan than wooden ones.
Can reduce public access along beach and cause extra erosion further down coast as beach material cannot move naturally by Longshore drift.

37
Q

How do gabions help maintain a coastline?

A

Short term measure to stabilise cliff bases.
A metal cage, measuring about 1m by 1m, that is built on site from 6 metal mesh sides and then filled with local rocks.

38
Q

How sustainable are gabions at maintaining a coastline?

A

Rust and can be damaged during severe storms, do not provide long term solution.
Have low cost.

39
Q

How is soft engineering for a coastline?

A

More sustainable than hard engineering.
Do not involve large-scale building, often take advantage of natural processes to be effective.
Have low costs, both economically and environmentally, so have become favoured choice for modern coastline engineers.

40
Q

How does beach nourishment maintain a coastline?

A

Large amounts of sand brought onto beach from somewhere else and deposited to help make wider or deeper beach to protect land behind it absorbing waves’ energy.

41
Q

How sustainable is beach nourishment at maintaining a coastline?

A

Cheap (£3000 per metre) but needs lots of maintenance, sand will be eroded away.

42
Q

How does managed retreat help maintain a coastline?

A

People decide to move their land uses further away from coast so cannot be eroded.

43
Q

How sustainable is managed retreat at maintaining a coastline?

A

May mean paying people compensation to move inland, allowing their houses to fall into sea.
May upset people, but more long term solution.

44
Q

What are the strategies used in coastal management at Newcastle, Co. Down?

A

Groynes - concrete groynes built on beach in 1980s.
Gabions - new wire mesh boxes filled with local stone placed near mouth of River Shimna in 2006.
Sea wall - originally built in Victorian era (late 19th century) and new one built since 2002.

45
Q

What were the impacts of groynes on Newcastle, Co. Down?

A

Trapped sand which was moving north-east.
Lasted about 20 years, then decayed and were useless.

46
Q

What were the impacts of gabions on Newcastle, Co. Down?

A

Protect recreation ground.
Have stabilised area of coast to allow pedestrians to use footbridge to access rest of promenade.
Earlier gabions decayed over time and had to be replaced.

47
Q

What were the impacts of the sea wall on Newcastle, Co. Down?

A

Original wall protected buildings in Newcastle for many years.
Storm in 2002 washed large parts of wall away.
New wall is curved so wave energy directed back out to sea, instead of attacking bases of wall.
Reflected waves increasing erosion of beach on way back down it.

48
Q

How sustainable are the groynes at Newcastle, Co. Down?

A

Protected beach for while, resulting in more tourist enjoyment.
However, groynes do not last long, eventually have to be replaced, expensive.

49
Q

How sustainable are the gabions at Newcastle, Co. Down?

A

Maintain an important tourist attraction.
Able to break up wave energy better than wall or other methods, seem to have been successful.
However, gabions need to be replaced after a time, expensive.

50
Q

How sustainable is the sea wall at Newcastle, Co. Down?

A

Original wall enabled development of boarding houses and hotels, and protected them for significant period of time.
However, sea walls not invincible and can be eroded. Very expensive to replace - new project cost £4 million.
If beach is eroded, will not be able to protect coast behind it. Fewer tourists will enjoy Newcastle if beach quality is poor, bring less money to town.
Any coastal management project has complicated impacts on natural processes of erosion, Longshore drift and deposition. Wall May have inadvertently caused erosion of beach.