Systems concepts on the coast

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  • Systems concepts on the coast
    • System
      • A process or collection of processes that transforms inputs into outputs.
        • 3 properties
          • Elements - parts that make up a system.
          • Attributes - characteristics of the elements that may be perceived and measured.
          • Relationships - associations that occur between elements and attributes.
      • Common characteristics
        • Abstractions of reality.
        • Behaviour: inputs, outputs, energy.
        • Functional as well as structural relationships.
      • Closed system - transfer of energy into and beyond the system but no transfer of matter.
      • Open system - both energy and matter transfer freely into and out of the system.
      • Isolated system - no interactions with anything outside the system boundary; no input or energy of matter.
      • Inputs: energy (waves, wind, tides) and matter (sediment, fluvial processes of erosion, glaciation, cliff/coastline erosion & sub-aerial erosion.
      • Stores/processes: beaches, sand dunes, salt marshes, cliff and wave-cut platforms.
      • Components: erosional and depositional coastal landforms.
      • Outputs: dissipation of wave energy, accumulation of sediment above tidal limit, sediment removed beyond cells.
    • Feedback
      • Feedback mechanism - a process that use the conditions of one component to regulate the function of the other.
      • Two types of feedback
        • Positive feedback - feedback where there is a progressively greater change from the original condition of the system.
          • E.g. trampling on sand dunes - causes erosion of sand and damage to vegetation - blowout.
        • Negative feedback - feedback keeps a system in its original condition.
          • E.g. fishtail groynes - change destructive waves into constructive waves - wave length increases and wave height decreases - more deposition.
    • Equilibrium
      • Coasts are dynamic.
      • The morphology of the coast responds to changes in energy because it aims to exist in a state of equilibrium with the reigning processes.
      • Dynamic equilibrium - the balanced state of a system when its inputs and outputs are equal.
        • Depends on 1. supply of sand 2. wave energy 3. sea level change 4. location.
      • Steady state equilibrium - where variations in energy and the morphological response in a situation do not deviate too far from the long-term average.
        • E.g. along a coast with consistent wave energy conditions, there may be a steep gradient at some times of the year and shallower at others but the annual gradient remains fairly similar.
      • Meta-stable equilibrium - where an environment switches from two or more states of equilibrium and the switch stimulates by some sort of trigger.
        • E.g. the action of high energy events can rapidly switch a coastal system from one state to another.


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