Natural System

• Coasts are examples of open systems. This means that they have inputs that originate from outside the system and outputs to other natural systems.
• Coastal systems are open systems because they receive inputs + outputs into the lithosphere, atmosphere, hydrosphere, biosphere and cryosphere
• the coast can also be seen as a closed system when exmaining specific sediment cells
• Inputs


  Material or energy moving into the system from the outside
• Outputs


  Material or energy moving from the system to the outside
• Energy


  Power or a driving force
• Dynamic Equilibrium


  The balance within a constantly changing system
• The inputs in coastal systems include:

  • (Material / Sediment) Sea level change, etc
  • (Energy) Tides
  • (Energy) Wind
  • (Energy) Waves
• Examples of Flows in coastal systems include:

  • Wind-blown sand
  • Mass Movement
  • Longshore drift
• Examples of outputs in coastal systems include:

  • Sediment transfers beyond sedimement cells
  • Dissipation of wave energy
  • Evaporation
  • Ocean Currents
• The stores in coastal systems include:

  • Marsh Environments
  • Cliffs
  • Beaches
  • Sand Dunes
• examples of positive feedback at the coast

  1. As waves erode the cliff, material is released
  2. This material abrades the cliff, which results in even more cliff erosion
• examples of negative feedback at the coast

  1. As the shore is eroded, material makes the wave-cut platform wider
  2. This can absorb wave energy and reduce the impact at the base of the cliff
• A coastal system constantly strives to be in a state of dynamic equilibrium; it constantly adjusts to changing conditions while maintaining overall stability over time.
• Example of how coastal systems are in a state of dynamic equilibrium:

  1. A beach experiences sediment input from rivers and longshore drift, while erosion removes material due to wave action.
  2. If sediment supply decreases — perhaps due to human activities like dam construction — erosion may dominate, leading to coastal retreat.
  3. However, if natural processes or restoration efforts replenish sediment, the system can regain balance.
  4. This continuous adjustment of inputs and outputs keeps the coastline in a state of dynamic equilibrium
• Specific example of how coastal systems are dynamic equilibrium: 


  1. Spurn Head formed due to longshore drift.
  2. This process continuously deposits sediment at the spit’s tip, extending it into the Humber Estuary.
  3. Storms and strong waves frequently erode the spit, removing sediment and threatening its stability.
  4. When sufficient sediment from cliff erosion along the Holderness Coast can help it maintain its structure.
  5. But if sediment supply is reduced —e.g., due to coastal defences— Spurn Head may be breached or even washed away.
  6. A constant balance between deposition and erosion