2B.5c

Question 1

What is the sediment cell concept an example of

Answer 1

The sediment cell concept (sources, transfers and sinks) is important in understanding the coast as a system with both positive and negative feedback, it is an example of dynamic equilibrium

Question 2

What is the sediment cell

Answer 2

A sediment cell (or littoral cell) is a linked system of sources, transfers and sinks of sediment along a section of coastline

Question 3

State an example of a sediment cell

Answer 3

​Flanborough head - source region
Holderness coast - transfer zone
Spurn head - sink region

Question 4

What is dynamic equilibrium

Answer 4

Negative – cliff collapse creates protective debris
Positive – storms erode sand dunes and can’t recover; SLR erodes a spit, and sediment isn’t replaced

Question 5

Compare closed vs open systems

Answer 5

• Closed: large natural barriers might stop sediment being moved between, or out of cells – e.g. Thames Estuary, Start Point Headland.
• Semi-closed: small material could make it out of cells, or between sub-cells, e.g. Christchurch Harbour
• Open: Wind, tides, or tidal currents might remove material

Question 6

Describe sediment cells further

Answer 6

• Stretches of coastline where the movement of material is mainly self-contained
• Closed systems of inputs (erosion), transport, outputs (deposition)

Question 7

What are sediment cells inputs

Answer 7

• From cliffs, headlands, rivers, lagoons by coastal erosion processes (HA, Att, Ab, Cor)
• OR: deposited by rivers in coastal environments
  Cliff erosion,
  Onshore currents
  River transport
  Wind blown (aeolian) sediment from land
  Subaerial processes
  Marine organisms

Question 8

How does deposition into shores occur

Answer 8

• Gravity settling (energy is too low), or Flocculation (small clay particles attracted, clump together)
• Might be a beach, e.g. Slapton Sands, or offshore, e.g. Dolphin Bank

Question 9

What transports sediment around the sediment cell

Answer 9

By littoral drift
Longshore drift
Swash
Backwash
Tidal currents
Sea/ocean currents
Wind (onshore, offshore or along shore)

Question 10

State some sediment outputs

Answer 10

Backshore depositional landforms
E.g. sand dunes
Foreshore depositional landforms
E.g. beaches
Nearshore depositional landforms
E.g. bars
Offshore depositional landforms
E.g. barrier islands

Question 11

Describe dynamic equilbrium

Answer 11

• Dynamic equilibrium (in this instance) is reached when inputs of sediment from the source region are balanced by the amount being deposited in sinks.
• It’s dynamic because although it’s in balance, there’s a constant movement of sediment through the system.
• the size of the landforms in the transfer zone will remain the same. (But not the ones in the source and sink regions)

Question 12

What might change the dynamic equilibrium

Answer 12

• E.g. climate change creating more frequent storms or erosion of the cliff line to a more resistant rock type.
• The system’s equilibrium may be interrupted (e.g. during a storm event) but they tend to return to balance on average over time due to negative feedback.
• Seasonal change (e.g. storms and strong winds during winter) will change the dynamic equilibrium