Coastal Systems And Landscapes

Question 1

What is a coast?

Answer 1

• Narrow zone where land and sea overlap.
• Dynamic environment - influences from atmospheric, terrestrial and marine processes and from humans

Question 2

How can the coast change over different time scales?

Answer 2

• hours - tides
• days - weather - waves
• weeks/months - erosion/transport
• years - development of landforms
• millennia - sea level change

Question 3

Coastal System Inputs

Answer 3

• wave energy
• wind energy
• tidal energy
• sea currents
• sea level change
• longshore drift

Question 4

Coastal System Stores

Answer 4

• Erosion landforms (e.g. cliffs)
• depositional landforms (e.g. spits, beaches)

Question 5

Coastal System Outputs

Answer 5

• dissipation of wave energy
• accumulation of sediment ABOVE the tidal limit
• sediment removed beyond local sediment cells

Question 6

Coastal Systems Key Flows/Transfers

Answer 6

• erosion
• mass movement
• weathering
• transportation
• deposition

Question 7

Negative Feedback in Coastal System example

Answer 7

Diminishing effect

1. Beach in dynamic equilibrium
2. Sediment eroded from beach during storm by destructive waves
3. Sediment deposited offshore (forming an offshore bar)
4. Waves forced to break out a sea. Energy dissipated and reduces erosion of beach.
5. After storm, constructive waves return and redistribute sediment from offshore bar back onto the beach.
6. Dynamic equilibrium

Question 8

Positive feedback in Coastal System example

Answer 8

Amplifying effect

1. Vegetation on sand dune trampled on by tourists
2. Sand becomes exposed
3. Sand eroded by the wind
4. Vegetation struggles to re-grow and hold the dunes together.
5. Back to step 2 and repeat

Question 9

What is a sediment cell?

Answer 9

A stretch of coastline within which the processes of erosion, transportation and deposition operate and the movement of sediment is largely-self contained.

Question 10

Division of sediment cells

Answer 10

• considered as “closed systems” but in reality small amounts of sediment can move from one cell to another.
• larger cells divided into sub-cells
• separated by well-defined boundaries, like headlands and stretches of deep water

Question 11

Sources of Sediment

Answer 11

• weathering and mass movement
• rivers and estuaries
• marine organisms (coral, shells etc)
• offshore currents (waves, tides etc)
• longshore currents
• cliff erosion

Question 12

Transport and stores/sinks (sediment)

Answer 12

• longshore currents redistribute sediment within the cell
• sediment gained from eroding sections of the coastline, called ‘sources’ and lost to sections experiencing deposition called ‘sinks’

Question 13

Examples of sinks

Answer 13

• beaches
• spits/bars/tombolos
• offshore bars/ sand banks

Question 14

Sediment budgets

Answer 14

• the balance between inputs (usually from erosion) and outputs (usually from deposition) is called the sediment budget
• where inputs exceed outputs, there is a positive budget and a surplus of sediment
• where outputs exceed inputs there is a negative budget and a deficit of sediment