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Wave Transportation and Deposition (Sediment cell / littoral cell…
Wave Transportation and Deposition
Transportation
Bedload
Traction: Grains moved through continuous contact with the sea floor
Saltation: Grains moved through discontinuous contact with the sea floor
Suspended load
Grains are carried by turbulent flow and are held up by the water
Deposition
Deposition is decided by sediment size (mass) and shape
Sediments can sometimes stick together and therefore become heavier and fall out in deposition
Sediment cell / littoral cell
Simplified model that examines coastal processes in a specific area
Movement of material within is largely self contained - sediment is largely recycled within rather than consisting of major outputs and inputs
Sediment cells are determined by the topography of the coastline which directs the movement of sediment within the cell
Boundaries of the cell are usually headlands or peninsulas
Dynamic equilibrium
States that the littoral cell is the result of inputs and processes that operate within it
A change in one input leads to a knock on effect on processors that leads to a change in .the landforms over time
For example: Cliff collapse --> increased sediment --> change in long-shore drift + transportation --> change in landforms
The balance changes and so therefore the dynamic equilibrium is changed
Human impacts on processes and system
Building of dams can reduce the supply (input) of sediment to beaches which will disrupt and change the dynamic equilibrium
Buildings can destabilise cliffs and cause them to collapse
Movement and transportation of sediment can be changed or disrupted and moved offshore due to the building of harbours and other coastal buildings
Example of human impacts
Southern California
Reduced supply of sediment by 33% due to building of dam
Harbour in the north is blocking southward movement of sediment and most is now diverted into offshore currents
West Africa
Building of Akosombo dam disrupts the flow of sediment from river volta which prevents it from reaching the coast
Less sand is reaching the beach and causing further erosion
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