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Y11 GEOGRAPHY > COASTS > Flashcards

COASTS Flashcards

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1
Q

Hydraulic action?

A

The sheer force of waves breaking against the cliff will cause parts of the cliff to break away. As waves hit the cliff face air is compressed in cracks in the rock blasting away small rock fragments.

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2
Q

Attrition?

A

Rocks and pebbles collide with each other as they are moved by the waves. This action makes the pebbles rounder, smaller and smoother
​

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3
Q

Abrasion/corrasion?

A

During storm conditions waves pick up sand and pebbles. When waves break the sediment that they have been carrying is hurled at the cliff face, wearing it away.

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4
Q

Factors affecting waves

The coastline is exposed to a large fetch

A

The larger the fetch the larger the waves generated. Larger waves have more power and energy for erosion therefore increasing the rate of erosion.

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5
Q

Factors affecting waves

Strong winds blow for a long time and create destructive waves

A

The longer waves blow for the more energy they generate. If waves generate more energy and become destructive they have more erosive power increasing the rate of erosion.

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6
Q

Factors affecting waves

There are soft rocks

A

Soft rocks are more easily eroded by destructive waves. This therefore increases erosion.

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7
Q

Factors affecting waves

A rock has many joints

A

If a rock has many cracks and joints, it has more areas of weakness which are more easily exploited by erosion. This increases the rate of erosion.

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8
Q

How do waves form?

A
  • formed by the wind blowing over the sea

- friction with the surface of the water causes ripples to form and these develop into waves

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9
Q

What factors affect waves?

A
  • The speed of the wind- stronger winds results in stronger waves because more energy is transferred to the waves
  • How long the wind has been blowing- the longer the wind has been blowing, the more energy is transferred and the stronger the waves
  • The fetch (the maximum distance of the sea that the wind can blow over)- the longer the fetch, the greater the possibility of large wave
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10
Q

Swash?

A

When waves break, the water that rushes up the beach is called the swash

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11
Q

Backwash?

A

The water then rushes back down the beach towards the sea, this is called the backwash

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12
Q

Coastal erosion?

A

The removal of material by the waves

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13
Q

Destructive wave chacteristics?

A

● Wavelength: Short wavelength (10-14 waves per minute)
● Wave height: High (above 1m)
● How it breaks onto the beach: Plunges
● Beach steepness: Steep
● Power of swash: Weak
● Power of backwash: Strong
● Their impact on the beach: Destroy the beach

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14
Q

Constructive waves chacteristics?

A

● Wavelength: Long wavelength ( 8-10 waves per minute)
● Wave height: Low (below 1m)
● How it breaks onto the beach: Spills
● Beach steepness: Gentle
● Power of swash: Strong
● Power of backwash: Weak
● Their impact on the beach: Build the beach

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15
Q

Suspension?

A

Suspension-​ ​Fine, light material is held up and carried by the water

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16
Q

Coastal transport?

A

Coastal transport takes place in two different ways, it can:
● Move material onto the beach (​Suspension, Saltation, Traction​)
● Move material along the coast (​Longshore Drift​)

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17
Q

Traction?

A

Large boulders and
rocks are rolled along the
seafloor

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18
Q

Saltation =

A

Small pebbles and
stones are bounced along the seafloor. The load is alternatively lifted then dropped representing the rise and fall in the velocity of the water

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19
Q

Solution?

A

Minerals are dissolved

and carried by the water. This process particularly affects cliff lines made up of limestone and chalk

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20
Q

Longshore drift?

A

Longshore Drift is the process whereby material is transported along the shore.

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21
Q

How does longshore drift work?

A
  • The waves approach the beach at an angle which is determined by the prevailing wind direction e.g. south-westerly winds would cause the waves to move east
  • The swash carries material up the beach at a 45 degree (oblique) angle

-The backwash then carries material back down the beach at a 90 degree angle
under gravity

-The material is continually carried along the coastline in a zig zag fashion until the material is deposited

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22
Q

Coastal deposition?

A
  • Coastal deposition is when waves drop and leave behind the load they were transporting
  • The deposited load is called sediment
  • Deposition results in more sediment staying on the beach than is taken away by the backwash
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23
Q

Coastal deposition, in low energy environments, e.g, sheltered bays where constructive bays are dominant?

A

In low energy environments such as sheltered bays there is less wind meaning the waves have less energy to transport material. This results in some material being deposited.

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24
Q

Coastal deposition, If there is a large source of sediment e.g. from a rapidly eroding headland

A

If there is too much sediment the waves will not have enough energy to carry all of the material therefore some of it will be deposited.

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25
Q

Coastal deposition, If material is caught behind a spit

A

The area behind a spit is a low energy environment meaning it is sheltered from the wind and waves. As a result of these low energy conditions there is not enough energy to transport material therefore it is deposited.

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26
Q

Coastal deposition, Where engineering structures like groynes have been built to trap sediment

A

Engineering structures such as groynes trap sediment and restrict longshore drift resulting in material being deposited.

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27
Q

Mass movement?

A

The downslope movement of rock, soil or mud under the influence of gravity

28
Q

Mass movement, rockfalls?

A

On cliffs of 40 degrees or more, especially if the cliff face is bare, rocks may become detached from the slope by physical weathering processes. These then fall to the foot of the cliff under gravity. Wave processes usually remove this material, or it may accumulate as a relatively straight, lower angled scree slope.

29
Q

Mass movement, slides?

A

These may be linear with movement along a straight line slip plane such as a bedding plane, or they may be rotational with movement taking place along a curved slip plane. In coastal landscape systems, these often occur due to undercutting by wave erosion at the base of the cliff which removes support for the materials above.

30
Q

Mass movement, slumps?

A

These are more common in weak rocks such as Clay which also become heavier when wet, adding to the downslope force. A layer of sand above a layer of clay may particularly encourage this, as rainwater passes through the sand but cannot penetrate the impermeable clay below increasing pore pressure in the sands.

31
Q

What is weathering?

A

Weathering is the breaking down of rock in situ (where it is)

● It is caused by day to day changes in the atmosphere such as extreme temperature

32
Q

Chemical weathering?

A

● Chemical weathering ​which is caused by a chemical reaction when rainwater decomposes rocks

33
Q

Mechanical weathering?

A

● Mechanical/physical weathering ​which results in rocks being disintegrated rather than decomposed

34
Q

Freeze-thaw?

A

This happens if rocks contain cracks. When it rains, water trickles into cracks in the rock, and the water freezes and turns to ice. Water expands when frozen which forces the cracks to open and then when the temperature warms up, the ice melts releasing the pressure placed on the rocks. Repeated freezing and thawing widens the cracks and weakens the rock so much that eventually pieces of rock begin to break off

35
Q

Salt-crystal growth?

A

This occurs when salt spray gets into cracks in the rock. The water may eventually evaporate leaving behind the salt crystals which over time grow in size. As they grow they exert (put) pressure on the rock causing cracks to become larger and the rock to become weaker

36
Q

Oxidation?

A

Oxidation is the reaction of rock minerals with oxygen, changing the mineral composition of the rock. When minerals in rock oxidize, they become less resistant to weathering

37
Q

Carbonation?

A

This occurs when carbon dioxide mixes with rainwater to produce a carbonic acid which attacks carbonate rocks like limestone

38
Q

Formation of a sea stack?

A
  1. A large crack is enlarged by wave processes such as hydraulic action. Due to further erosion the crack grows, turns into a notch and then a cave.
  2. Over time further erosion increases the size of the cave, and due to wave refraction waves attack all sides of the headland. This often results in caves forming back to back. The sea eventually breaks through the cave forming a natural arch e.g. Durdle Door Dorset.
  3. The base of the arch is eroded by wave action through processes such as hydraulic action and abrasion which forms notches in the base of the
    arch causing it to widen. Freeze thaw weathering continues to weaken the top of the arch making it less stable. As a result the top of the arch eventually collapses due to a lack of support. This leaves a pillar of detached rock called a stack e.g. Old Harry.
  4. Notches form at the base of the stack which makes it unstable. Eventually this causes the stack to topple leaving only its base. This is known as a stump e.g. Old Harry’s Wife.
39
Q

How headlands and bays form?

A
  • A discordant coastline has rocks of different hardness lying at right angles to the coastline.
  • Differential erosion means hard rocks like limestone and chalk are eroded at a slower rate than soft rocks such as sand clays. This has resulted in the formation of headlands such as Durlston Head and bays such as Swanage Bay on the Dorset coastline.
  • Once the headland and bay pattern has emerged, the processes operating on the coastline are reversed. The now sheltered bays become low energy environments where deposition occurs, and the exposed headlands become targets of erosion as a result of wave refraction
40
Q

Formation of spits?

A

● Spits are long, narrow fingers of sand or shingle jutting out into the sea and are created by the process of Longshore Drift
● Eroded material ends up caught up within the waves and is carried by the sea along the coastline
● Material is carried along the shore in a zigzag fashion by waves as the swash moves material up the beach at a 45-degree angle and the backwash moves material back down the beach at a right angle
● Wherever there is a break or change in the direction of the coastline material is deposited closest to the shore
● This is because there is often a reduction in velocity at a river mouth so material is dropped or deposited
● Eventually this material builds up out into the sea to form a Spit
● Due to tidal currents or changes in the wind direction, the spit
can become hook shaped at the end forming a low energy
environment behind it
● As a result, Spits often have mudflats and salt marshes building
up behind them because the spit offers protection from the
stronger waves and the wind, allowing salt tolerant plants to grow
● An example of a Spit is Sandbanks Spit Dorset

41
Q

Sand dune formation?

A

● Embryo dunes form around deposited obstacles such as pieces of wood or rocks
● These develop and become stabilised by vegetation to form foredunes and tall yellow dunes. Marram grass is adapted to the windy, exposed conditions and has long roots to find water. These roots help bind the sand together and stabilise the dunes
● In time, rotting vegetation adds organic matter to the sand making it more fertile. A much greater range of plants colonise these ‘back’ dunes
● Wind can form depressions in the sand called dune slacks. Ponds may form here

42
Q

Hard engineering?

A 
Hard engineering is when expensive artificial structures are used for protection. They are effective, but often do not blend in well with the natural environment
Examples of hard engineering include: 
● Sea walls
● Gabions
● Rock armour
● Groynes
43
Q

Soft engineering?

A 
Soft engineering works more in harmony with nature compared with hard engineering. It is generally less expensive and less effective
Examples of soft engineering include:
● Beach nourishment
● Managed retreat
● Dune regeneration
● Dune fencing
44
Q

Hard engineering, sea walls

How it protects the coast

A

Sea walls provide a barrier between the waves and the land, and are usually placed along the back of the beach. Recurved sea walls are more expensive than flat sea walls, but are more effective in reflecting waves and reducing overtopping. The recurved face rotates the waves backwards so that some of the energy is reflected back out to sea. This impedes the next wave and reduces its energy, reducing its erosive power

45
Q

Hard engineering, sea walls advantages

A

Social:​ ​A sea wall gives people a sense of security that the coastline is being protected. Sea walls often have promenades on top of them which can be used as walk and cycle paths. Steps at the base of the wall act as seating areas for beach users

Economic: ​If well maintained, sea walls can last for many years

Environmental:​ ​Sea walls do not impede the movement of sediment down drift so they do not disadvantage other areas

46
Q

Hard engineering, sea walls disadvantages?

A

Social:​ ​They restrict people’s access to the beach, and if the waves break over the sea wall, coastal flooding may occur

Economic:​ ​At about £5,000 per metre, sea walls are expensive to build. Repairs are also expensive. Reflective waves can also scour the beach in front of a sea wall and this undermines the foundations. If damage is not repaired quickly, the result may be devastating.

Environmental:​ ​From the beach, a wall of concrete is ugly to look at. Sea walls can also destroy habitats

47
Q

Hard engineering, gabions

How it protects the coast

A

Gabions are steel wire mesh cages filled with pebbles or rocks. They are placed at the back of a sandy beach to create a low wall-like structure. Water enters the cages and the rocks absorb and dissipate some of the waves’ energy, reducing the rate of erosion. Gabions may also be placed in front of a cliff where they can be covered in vegetation giving the cliff stability and reducing the risk of landslides

48
Q

Hard engineering, gabions

Advantages

A

Economic:​ ​At £110 per metre, they are relatively cheap and easy to construct. This is because gabions are often constructed on site using local pebbles, making them cheaper than sea walls, rock armour and groynes. For the price, they are good value for money and may last for 20-25 years.
Environmental:​ ​They blend in better than other hard engineering methods, especially when sand is blown into them or when they are covered by vegetation.

49
Q

Hard engineering, gabions

Disadvantages?

A

Economic:​ ​The use of gabions is restricted to sandy beaches, as shingle being hurled at them would quickly degrade them. Gabions are easily destroyed, so regular maintenance is needed, and the repair of embedded, vegetation covered gabions can be expensive.
Social:​ ​In a damaged state, gabions are dangerous as people may trip over them or cut themselves on the broken wire.
Environmental:​ ​Damaged gabions are unsightly and sea birds may damage their feet on them.

50
Q

Hard engineering, rock armour

How it protects the coast

A

Rock armour (rip rap) is made up of thousands of tonnes of huge boulders of hard rock like granite which act as a barrier between the land and the sea. Boulders are generally big enough not to be moved by the storm waves. They are arranged at a downward slope angle to the sea which deflects the waves’ energy. As water enters gaps between the boulders, pressure is released by the waves, reducing their energy therefore reducing erosion.

51
Q

Hard engineering, rock armour

Advantages

A

Economic:​ ​Rock armour is relatively cheap, costing £1000-3000 per metre compared to £5,000 per metre for a sea wall. The structure is quick to build and can be built in a matter of weeks rather than months. The structure is also easy to maintain, and if maintained well, rock armour can last a long time. Rock armour is also versatile and can be placed in front of a sea wall to lengthen its life span.

52
Q

Hard engineering, rock armour disadvantages

A

Social:​ ​Rock armour makes access to the beach difficult as people have to clamber over it or make long detours. People may have accidents when clambering over it as rocks may be unstable, and if rocks are regularly covered by the tide, they may collect slippery seaweed which increases the hazard.
Economic:​ ​Highly resistant rocks from Norway and Sweden are often used in preference to rocks from local quarries. This may cause resentment as well as inflating the costs of the rip rap as they have to be imported. Rip rap may also need regular maintenance after storms as strong waves may move and loosen the boulders. Environmental:​ ​Rock armour is ugly and often covers vast areas of the beach. Driftwood and litter can become trapped in the structure, and imported rocks do not blend in with the local geology

53
Q

Hard engineering, groynes

How it protects the coast

A

Groynes are wooden or stone structures built in the foreshore and look like fences or walls. They are built at right angles to the beach and are spaced at regular intervals, approximately 50 metres apart. Traditionally, groynes were made of hardwood timber, however stone groynes are now more popular as wooden ones can rot over time. Groynes trap sediment transported by longshore drift. This builds up the beach on the updrift side of a groyne. A larger beach provides a more effective buffer as it absorbs the waves’ energy and reduces the impact of waves on the sea wall. Groynes are particularly effective when used with beach nourishment.

54
Q

Hard engineering, groynes

Advantages

A

Social:​ ​Rock groynes at sandbanks have concrete crests for people to walk along to reach a viewing or fishing point. Groynes also act as windbreakers.
Economic:​ ​At £5,000 each, groynes are relatively cheap and if well maintained, can last up to 40 years. A larger beach, with more space for activities, attracts more tourists which boosts the local economy.

55
Q

Hard engineering, groynes

Disadvantages

A

Social:​ ​Groynes are barriers which impede walking along a beach and are also dangerous as they have deep water on one side and shallow water on the other. This is a particular hazard to children who find it hard to resist climbing on them.
Economic:​ ​By trapping sediment, groynes restrict the supply of sediment down drift. Groynes are also ineffective in storm conditions and need regular maintenance so that they do not rot. Environmental:​ ​Groynes may be considered unattractive, especially degraded ones.

56
Q

Soft engineering, dune fencing

How it protects the coast

A

Fences are constructed on a sandy beach along the seaward face of existing dunes to encourage new dune formation. These new dunes help protect the existing dunes.

57
Q

Soft engineering, dune fencing

advantages

A

Economic:​ This method is cheap at around £400 to £2000 per 100m. Environmental: ​This method has minimal impact on natural systems and the fences can control public access to protect other ecosystems.

58
Q

Soft engineering, dune fencing

Disadvantages

A

Social/Environmental: ​Dune fencing can be unsightly especially if the fences become broken
Economic:​ ​Regular maintenance is needed especially after storms.

59
Q

Soft engineering, dune regeneration

How it protects the coast

A

Sand dune regeneration is the artificial creation of new sand dunes or the restoration of existing dunes. Sand dunes act as a physical barrier between the sea and the land. They absorb wave energy and water and therefore protect the land from the sea.

60
Q

Soft engineering, dune regeneration

Advantages

A

Social:​ ​Sand dunes protect land uses behind them. Once established, they are popular as picnic and walking areas Economic:​ ​Small planting projects often use volunteer labour and local grass for transplants so costs are minimal
Environmental:​ ​At Studland sand dune, regeneration has helped maintain a habitat for rare species such as nightjar, warblers and chiffchaffs

61
Q

Soft engineering, dune regeneration

Disadvantages

A

Social:​ ​While becoming established, regenerated sand dunes are fenced off with signs to tell people to keep out. This may deter tourists.
Economic:​ ​Dune regeneration has to be checked
Environmental:​ ​Sand dunes are a dynamic environment, once regenerated; there is no guarantee that they will be stable. The grass may soon be damaged by storms, and even in favourable conditions, it may take two or three years before grasses become established and begin to spread.

62
Q

Soft engineering, beach nourishment

How it protects the coast

A

Beach nourishment is a broad term for the replacement of lost sediment. A nourished beach means fewer waves reach the back of the beach. As more wave energy is absorbed and dissipated by the beach, the rate of erosion is reduced.

63
Q

Soft engineering, beach nourishment

Advantages

A

Social:​ ​A wider beach means more room for beach users and people living along the seafront are more protected from coastal flooding Economic:​ ​At sandbanks, the wider, nourished beach protects very expensive properties. The buffer of a widened beach reduces sea wall maintenance costs. A broader beach may also attract more tourists. Environmental:​ ​A nourished beach is natural and blends in with the environment

64
Q

Soft engineering, beach nourishment

Disadvantages

A

Social:​ ​During re-nourishment, access to the beach is restricted for several weeks. Beach recycling may cause resentment from residents living close to the donor area.
Economic:​ ​Although cheaper than hard engineering options, this has high overheads as it costs around £300,000 to hire a dredger. The 137,000 metres of nourishment at Sandbanks in 2014 cost £195 million.

65
Q

Soft engineering, managed retreat

How it protects the coast

A

Managed retreat is a deliberate policy of allowing the sea to flood or erode an area of relatively low value land. It is a form of soft engineering as it allows natural processes to take place and does not intervene in the way that hard engineering does.

66
Q

Soft engineering, managed retreat

Advantages

A

Social:​ ​It may help take the pressure off areas further along the coast and reduce their risk of flooding
Economic:​ ​It is often cheaper in the long term to use managed realignment than to continue to maintain hard engineering defences
Environmental: Managed alignment is designed to conserve or enhance the natural environment. It also creates new habitats for those lost through coastal squeeze.

67
Q

Soft engineering, managed retreat

Disadvantages

A

Social:​ ​Various villages and homes will be destroyed and the relocation of people to new homes causes disruption and distress
Economic:​ ​Short term costs may be high as relocation costs have to be paid
Environmental:​ ​Large areas of agricultural land are lost and habitats of coastal birds e.g. Cranes would be affected and bird numbers would decline.

Y11 GEOGRAPHY (16 decks)

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