However, a rebuilt beach is not identical to the beach that existed before the storm. The natural balance of these three factors is called dynamic equilibrium. When one factor changes, the others adjust to maintain the natural balance. Dune Building and Vegetation Sand dunes are mounds or ridges of beach sand deposited by wind. Their shape is determined by the amount of sand available and the prevailing wind direction.
Dunes occur when dry sand begins to build at some obstacle, such as plant debris or a shell.
If a plant grows on the mound that results, the mound will begin to grow larger. As it blows around vegetation, the wind's speed is reduced, causing sand grains to drop. Plant roots help to stabilize the sand. Few plant species are able to thrive in the harsh beach or dune environment. To survive, they must be able to tolerate salt spray, extreme heat, drought, sand blasting and burial, and low nutrient supply.