Coastal Dunes and their Distribution
Dunes build up in response to the onshore transport of sediment
Dry conditions and a large sediment supply are typically necessary for large-scale dune
development
They are stabilized by vegetation and trap the sand/silt from blowing back offshore
Develop in the back beach (supratidal) area or on a barrier island.
Progradation of dunes is possible landward
Large dunes form by transport of sediment up the windward side of the dune and often slope
failure and avalanche down the leeward side of the dune.
When lithified, there is often CROSS BEDDING-showing the interior stucuture of the leeward
(preserved) side of the dune)
Pavements form when larger particles that can’t be moved by the wind are left behind as a lag
deposit and armor the surface from further erosion.
Dunes may erode the sediment down to the water table, where the wet sediment can no longer be
moved by the wind.
Dunes are the best protectors of coastal areas. Land management now minimizes the destruction
of the dunes