Beaches and dunes form a flexible, natural system that absorbs and responds to the forces of the sea. About one half of the South Australian coastline is made up of sandy beach backed by dune.
Coastal dunes are formed when there is a supply of sand delivered to the beach by waves and blown landward by onshore winds. Dunes are stabilised and built up when coastal dune vegetation traps and binds the sand with its leaves and extensive root systems. This reservoir of trapped sand is considered to be integral in maintaining a natural beach system and the associated sand cycle of erosion (loss of sand) and accretion (build-up of sand).
The beach/dune system also offers another very important ecosystem function by providing a buffer between the land and the sea, protecting landward vegetation from high energy storms and wave action. In more recent times, natural and built sand dunes have played a vital role in protecting coastal development from ongoing coastal hazards such as inundation and erosion.