coastal dune

Immediately landward of the beach are commonly found large, linear accumulations of sand known as dunes. (For coverage of dunes in arid and semiarid regions, see sand dune.) They form as the wind carries sediment from the beach in a landward direction and…

…are widened and beach ridge dunes or cheniers may be formed. During a transgressive stage the saltwater wedge at river mouths causes a back-up, and the estuary becomes much more sluggish (thalassostatic).