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Physical Geography > Coastal Transport and Deposition > Flashcards

Coastal Transport and Deposition Flashcards

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1
Q

What are the four processes of sediment transport?

A
  • Saltation
  • Solution
  • Traction
  • Suspension
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2
Q

Saltation

A

Transport of sand-sized particles. Sediment bounces along, either due to the force of water or the wind

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3
Q

Solution

A

Transports chemical compounds in solution. Dissolved material is carried in the water as a solution.

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4
Q

Traction

A

Pebbles, cobbles, boulders. Sediment rolls along, pushed by waves and currents

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5
Q

Suspension

A

Silt and clay particles. Sediment is carried in the water column

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6
Q

Currents

A

Flows of seawater in a particular direction driven by winds or differences in water density, salinity or temperature.

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7
Q

Longshore Drift

A

The net transport of sediment along the coastline that contributes to many depositional landforms.

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8
Q

How does longshore drift work?

A

Wave crests approach the beach at an angle (rather than 90 degrees to the coast), the swash from the breaking waves and the resulting backwash follows different patterns up and down the beach in a zig zag pattern. The result is net sediment transport along the beach and a longshore flow of sediment.

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9
Q

What causes the dominant direction of longshore drift?

A

The dominant prevailing wind

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10
Q

When is sediment deposited along coastlines?

A

When the force transporting the sediment drops

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11
Q

What are the key sources of sediment for depositional landforms on coasts?

A
  • longshore drift

- sediment transported down the coast from river systems or offshore sources are also important

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12
Q

How can deposition occur?

A
  • Gravity settling

- flocculation

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13
Q

Gravity settling

A

When the energy transporting water becomes too low to move sediment. Large sediment will be deposited first.

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14
Q

Flocculation

A

A depositional process that is important for very small particles such as clay, which are so small that they remain suspended in water. Clay particles clump together through electrical or chemical attraction, and become large enough to sink.

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15
Q

The main depositional landforms

A
  • Spit
  • Bayhead beach
  • Tombolo
  • Barrier beach/bar
  • Hooked/recurved spit
  • Cuspate foreland
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16
Q

What is a spit?

A

A sand/shingle beach ridge extending beyond a turn in the coastline, greater than 30 degrees.

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17
Q

How is a spit formed?

A

At the turn in the coastline, the longshore drift current spreads out and loses energy, leading to deposition. Length of the spit is determined by the existence of secondary currents causing erosion, either the flow of river or wave action which limits its length.

18
Q

Example of a spit

A

Spurn head, Holderness coast

19
Q

What is bayhead beach?

A

Beach formed in a bay

20
Q

How is a bayhead beach formed?

A

Waves break at 90 degrees to the shoreline, move sediment into a bay, where a beach forms. Through wave refraction, erosion is focused at headlands and bays become an area of depositon

21
Q

Example of a bayhead beach

A

Lulworth Cove, dorset

22
Q

What is a tombolo?

A

A sand or shingle bar which links the coastline to an offshore island.

23
Q

How are tombolos formed?

A

Tombolos form as a result of wave refraction around an offshore island which creates an area of calm water and deposition takes place between the island and coast. Opposing longshore current may play a role, and cause the landform to be similar to a spit.

24
Q

Example of a tombolo

A

St Ninian’s tombolo, Shetland

25
Q

what is a Barrier beach/bar?

A

A shingle/sand beach connecting 2 areas of land, with a shallow-water lagoon behind.

26
Q

How does a barrier beach/bar form?

A

Forms when a spit grows so long that it extends across a bay, closing it off.

27
Q

Example of a barrier beach/bar

A

Chisel Beach, Dorset

28
Q

What is a hooked/recurved spit?

A

A spit whose end is curved landward into a bay/inlet.

29
Q

How is a hooked/recurved spit formed?

A

Seaward end of spit naturally curves landward into shallower water. Hook can be made more pronounced by waves from a secondary direction to prevailing wind.

30
Q

Example of a hooked/recurved spit

A

Hurst castle spit, Hampshire

31
Q

What is a cuspate foreland?

A

A roughly triangular shaped feature extending out from a shoreline.

32
Q

How is a cuspate foreland formed?

A

Debates about formation but one theory is that they form from the growth of 2 spits in opposing directions.

33
Q

Example of a cuspate foreland

A

Dungeness, Kent.

34
Q

What role does vegetation play in depositional landforms?

A

Stabilises them. Plant succession as salt marshes and sand dunes binds loose sediment together and encourages further deposition.

35
Q

What is the sediment cell model?

A

the wider context of the coastal region/area. Long stretches of coastline operate as cells, 11 around the english and welsh coast. Sediment cell must be considered in order to ensure the success of erosion management projects.

36
Q

What is a source?

A

Places where sediment is generated, such as cliffs, eroding sand dunes, offshore bars and river systems.

37
Q

What is a transfer zone?

A

Places where sediment is moving along the shore through offshore currents and longshore drift. Beaches and parts of dunes perform this function.

38
Q

What is a sink?

A

Locations where the dominant process is deposition. Depositional landforms are creates, including spits and offshore bars

39
Q

What determines whether a place is a source or a sink?

A

Depends whether erosion or deposition is the most dominant process operating at the time

40
Q

How do negative feedback mechanisms restore the equilibrium in sediment cells?

A
  • EG erosion causes cliff collapse, but debris at base of the cliff protects it from further attack
  • erosion of sand dunes leads to deposition offshore, which forms an offshore bar, which reduces wave energy, and this allows sand dunes time to recover.
41
Q

What effect does human intervention have on the sediment cell?

A
  • coastal management and threats to sea level rise as a result of global warming
  • put the equilibrium at risk
  • positive feedback occurs, rising sea levels erodes spits and estuaries, removing material before it can be replenished.

Physical Geography (16 decks)

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