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Home arrow Articles by Topic arrow Erosion arrow Beach erosion
Beach erosion PDF Print
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Articles - Erosion
Written by OzCoasts   
Tuesday, 06 October 2009

Geological background

Beach deposits predominantly consist of sand particles that can be easily eroded by waves. These deposits comprise terrestrial sediment delivered to the coast by rivers, sediment produced by the erosion of coastal landforms by waves, and marine sediment that has been reworked from offshore deposits onto the coast. Sand derived from a terrestrial source is usually dominated by resistant minerals such as quartz. Marine sediments, however, comprise resistant minerals and biogenically-produced calcium carbonate.

The main pressures on beaches and dunes are urbanisation and developments associated with coastal tourism

The sand in many Australian beach systems is at least partially sourced from the continental shelf. Large volumes of this inner shelf sand have been pushed up the continental shelf as sea level rose following the end of the last glacial period (18,000 years ago), and has been accumulating on the present coast during the last 6,500 years of high and relatively stable sea level. On the southeast coast of Australia, large bodies of sand on the inner shelf are the remnants of coastal sand deposits emplaced when sea level was a few tens of metres lower than present. The rate of supply of sediment derived from the inner continental shelf varies between coastal regions, and in some has declined over the last few thousand years because over this period the volume of sediment available for reworking to the coast by wave-induced currents has gradually been reduced.

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