The coastal system

• Coastal system


  An open system that receives inputs from outside and transfers outputs away from the coast into other systems (terrestrial, atmospheric or oceanic)
• Coasts can be considered as a closed system in some circumstances such as during scientific research and coastline management planning
• The coastal system is impacted and impacts upon processes which occur in the five oceans of our planet and the smaller seas
• Habitats and activities affected by and affecting the coastal environment

  • Towns
  • Sediment cells
  • Coastal change
  • Marine waste
  • Atmosphere
  • Ocean currents
  • Evaporation
• Sediment cells


  • Stores and sinks of sediment and material
  • Formation of features like beaches, spits, bars, tombolos, headlands, bays, wave-cut notches, platforms, caves, arches, stacks, stumps, salt marshes, tidal flats, offshore bands and bars
• Sediment transport


  1. In suspension

  2. In solution

  3. By settling
• Energy


  The power and driving force behind sediment and flows in the coastal system
• Feedback loops in the coastal system

  • Positive feedback - mechanisms that amplify changes within the system
  • Negative feedback - mechanisms that balance and stabilise the system
• Negative feedback loop


  Destructive waves lose energy, excess sediment is deposited as an offshore bar

  2. Bar dissipates wave energy, protecting the beach from further erosion

  3. Over time the bar gets eroded instead of the beach

  4. Once the bar is gone, normal conditions resume and the system goes back to dynamic equilibrium
• Human activities can disrupt the state of dynamic equilibrium in the coastal system
• Sediment sources


  • Rivers
  • Cliff erosion
  • Wind
  • Glaciers
• Sediment budget


  Uses data of inputs, outputs, stores and transfers to assess the gains and losses of sediment within a sediment cell
• Sediment budgets operate in a state of dynamic equilibrium where inputs and outputs are equal, but can be disrupted by human actions and natural variation
• Littoral zone


  The area of land between the cliff/dunes and the offshore area beyond the influence of waves, constantly changing due to short-term factors like tides/storms and long-term factors like sea level change and human intervention
• Shore/Shoreline


  The boundary between the sea and the land
• Offshore


  The area beyond the influence of waves
• Onshore


  The area of land not covered by the sea, but very close to it