Sand Dunes

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The frontal dune has an essential role of acting as a barrier against the wind and waves and also provides a source of sand in times of erosion. Because the frontal dune protects the area behind, more complex plant communities can develop behind the dune. In storm events, the frontal dune plays the most important role in protecting the rest of the environment from the damaging effects of the waves and wind. In large storm events, the frontal dune is eroded and the sand shifts to form an offshore bar. Once conditions return to normal, this sand is slowly redistributed to the beach through wave action. In the case of severe storm events, parallel dunes landward of the frontal dune act as backup protection if the frontal dune is flattened. The wider this buffer of parallel dunes is, the more protection they offer to communities and infrastructure behind them.

Parallel dunes.jpg

Vegetation plays an important role in forming dunes. Dunes build in height and width as vegetation and debris trap windblown sand. The roots stabilise the dune and help prevent erosion by wind and waves. Berms form in front of the foredune as pioneer plant species such as Spinifex and goat’s foot colonise the area and trap the sand. Overtime, this berm will build up until it becomes the new frontal dune and the process a berm forming starts again. The figure above shows a series of parallel dunes that have formed in this way.

Dune Profile.jpg

Coastal values of the Dry Tropics

Resources

BDT Coastal Zone.jpg

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