1.1.1 The Operation of the Coast as a System

1.1.1 The Operation of the Coast as a System

1. Sediment cells

   • 11 largely self contained cells around England and Wales
   • Coastal system as a whole can be identified within this area
   • Usually confined by morphology of the coast e.g. between two headlands
   • Sediment brought from terrestrial (land) sources via watershed run-off and hillside erosion
   • Material can be lost from the cell via a submarine canyon
   • Cells are connected therefore if one cell is disrupted, neighbouring cells can be affected
   • Aka Littoral cells

2. The Process Response Method

   • The morphology of the coastal landforms are the result of the processes operating at the coast
     • Morphology = shape of coastline
     • e.g. Cliff retreat - the main process is erosion from destructive waves --> erosion of cliff base --> collapse --> changed the shape of the coastline

3. System feedback

   • Positive feedback
     • Amplifies the initial input
       • e.g. storm erodes at a beach and cause MORE erosion to occur at the back
   • Negative feedback
     • Mitigates the initial input
       • e.g. Eroded material can be moved offshore, reducing the energy of oncoming waves --> deposition --> LESS erosion occurs

4. Dynamic equilibrium

   • A state of balance within an ever changing system

5. There are two coastal subsystems

   • Beach
     • Aeolian transportation
     • Waves bringing in material
     • LSD moving sediment
     • Sediment budget
   • Cliff
     • Subaerial weathering
       • Chemical e.g. solution
       • Physical e.g. freeze-thaw
       • Biological e.g. plant roots exposing weaknesses in rock
     • Mass movement e.g. rockfall, slumping, rock toppling

6. The coastal system is a Dynamic Open system

   • Dynamic = constantly changing
   • Open system = material and energy can enter and leave

7. System is made up of components

   • Inputs
     • LSD in
     • Tides, waves and wind bringing in energy and sediment
     • Constructive waves
   • Transfers
     • Saltation
     • LSD moving material
   • Stores
     • Beaches
   • Outputs
     • Dredging
     • Destructive waves

8. Exam Question

   • A system is a collection of interrelated components that together form a working unit with inputs, outputs, transfers, and stores. Figure 1 shows a sub-sediment cell. Firstly, sediment is inputted from Arcachon estuary and sediment is also brought to the beach from offshore currents powered by prevailing winds. Figure 1 also shows the presence of Cap Ferret spit implying that there has been strong longshore drift which transfers sediment to Arguin offshore bar where it is deposited and held as a store. Beach sediment blown inland by the wind to form Dune du Pilat where sediment is outputted resulting in dynamic equilibrium.

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