The Coastal System

• What are coastal inputs?

  They input sediment into the system.

  Energy inputs come from winds, waves, tides and currents.
• What are coastal outputs?

  They transfer sediment out of the system.

  Energy outputs include waves resulting in transportation and deposition that deposit further down the coast.
• What are coastal flows and transfers?

  Processes that move sediment within a system.

  Flows and transfers include processes such as erosion, weathering, transportation and deposition.
• What are coastal stores/components?

  These store sediment in one place (temporal).

  Stores and components include landforms such as beaches, dunes, offshore bars and spits.
• Coastal systems are generally in dynamic equilibrium. What does this mean?

  The inputs and outputs are balanced.

  A change in one input or output often causes negative feedbacks that restore the balance of the system. Positive feedbacks can also occur (new equillibrium)
• What is negative (dynamic equilibrium) and positive feedback (new equilibrium) ?


  > Negative - A change in the system causes other changes that have the opposite effect e.g. a beach is eroded leaving the cliffs open to attack, sediment eroded from the cliff is deposited again on the beach resulting in it growing in size again.

  > Positive - A change in the system causes other changes that have a similar effect e.g. a beach begins to form which slows down the waves causing more sediment to be deposited, new equilibrium reached when long-term growth of the beach stops.
• How is wind a source of energy at the coast?

  > Winds are created by air moving from areas of high pressure to low pressure. The pressure gradient (difference) depends on the strength of the winds.

  > Strong winds can generate powerful waves. Prevailing winds can cause higher-energy waves compared to winds that frequently change direction.
• How are waves created?

  Waves are created by the wind blowing over the surface of the sea. The friction between the wind and the surface gives the water a circular motion.
• What is the effect of a wave on the shore?

  It depends on its height and whether it is a constructive or a destructive wave.

  Wave height is affected by the wind speed and fetch of the wave - high wind speed and long fetch create higher and more powerful waves.