Coastal dunes

A coastal dune is an accumulation of windblown sand immediately landward of the beach that acts as an important store of sand in the coastal sediment budget. During periods of shoreline erosion the sediment stored within the coastal dunes helps to mitigate the effects of shoreline change: dunes act as a protection against storm erosion and flooding during short-term seasonal change, and as a buffer or sand store to counteract a long-term erosive trend.

Just over half of the Australian coastline is sandy, and about half of this again is backed by sand dunes. South Australia has a higher proportion of dune coast than other states (53%), Western Australia has 30%, while the Northern Territory has the smallest proportion (6%). Dune fields along the eastern coast of the continent are almost entirely composed of quartz sands. The southern and western coast dunes are of quartz and carbonate sands in varied proportions, while the northern coasts are characterised by a lack of dune-building sand sediments. The European impact on Australia's coastal sand dune areas has been massive, due mainly to building, mining, and grazing. While the extent of clearance has not been documented, it can be said that there are few coastal areas that remain in a pristine state, little affected by burning or introduced plants or animals. Managing these unstable landforms has proved a challenge to land managers all round Australia.

Coastal dunes may extend inland from the highest tide mark for only a few metres or for several kilometres inland; they may be great sand masses more than 200 metres high or a series of low dune ridges on a flat coastal plain. The immediate source of sediment for the formation of coastal dunes is from the dry beach, and the development of coastal dunes is primarily due to the transport of sand by wind. Coastal vegetation, which operates to stabilise the wind-blown sand, is a vital element in the formation and maintenance of many dunes. Thus, coastal dunes are best developed in areas with strong onshore winds and an abundant sand supply, and where there is sufficient rain for vigorous vegetation growth.

 
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