Coastal Erosion (Shifting Dunes)

How Dunes Form

There are a number of conditions necessary for sand dunes to develop. There generally needs to be:

  1. A significant distance between the high and low water mark, exposing a vast supply of sand;
  2. Strong onshore winds and;
  3. A gently sloping shoreline.

The wind blows sand up the beach by a process known as saltation, until it meets an obstacle, such as driftwood, pebbles or marine debris on the strandline, which slows down the wind, causing it to deposit the sand it is carrying. Sand begins to pile up behind the object, allowing specialist plants to colonise, trapping more sand and beginning the process of dune formation. 

The youngest, smallest, dunes are found immediately behind the beach, running parallel to the shore. Older fixed dunes are found further inland. They tend to be more complicated shapes, facing in many different directions and are much higher.

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