Feedback Loops

• The coastal system has mechanisms which enhance changes within a system, taking it away from dynamic equilibrium (positive feedback) or which balances changes, taking the system back towards equilibrium (negative feedback).
• Negative feedback: lessens any change which has occurred within the system.

  For example: a storm can erode a beach, taking it out of dynamic equilibrium (larger input than output). A negative feedback loop will balance the excess by: depositing excess sediment as an offshore bar, which dissipates wave energy and protects the beach from further erosion. Overtime, the bar is eroded away and normal conditions ensue and returns to dynamic equilibrium.
• Positive feedback: exaggerates the change, making the system more unstable and taking it away from dynamic equilibrium.

  For example: people walking over sand dunes destroys vegetation and erodes. As the roots of the vegetation held the sand dunes together, damaging vegetation makes sand dunes more susceptible to erosion, increasing the rate of erosion. Eventually, the sand dunes will be completely eroded, leaving more of the beach open to erosion, taking the beach further away from its original state.