Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach.
In most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea. Artificial dunes are sometimes constructed to protect coastal areas. The dynamic action of wind and water can sometimes cause dunes to drift, which can have serious consequences.
Coastal dunes form when wet sand is deposited along the coast and dries out and is blown along the beach. Dunes form where the beach is wide enough to allow for the accumulation of wind-blown sand, and where prevailing onshore winds tend to blow sand inland. The three key ingredients for coastal dune formation are a large sand supply, winds to move said sand supply, and a place for the sand supply to accumulate.
Dunes are commonly grouped into either the Primary Dune Group or the Secondary Dune Group.
Primary dunes gain most of their sand from the beach itself, while secondary dunes gain their sand from the primary dune. Along the Florida Panhandle, most dunes are considered to be foredunes or hummocks.
Coastal sand dunes can provide privacy and/or habitats to support local flora and fauna. Animals such as sand snakes, lizards, and rodents can live in coastal sand dunes, along with insects of all types. Birds are also known to utilize coastal dunes as nesting grounds. These species find the coastal environment of the sand dune vital to their species’ survival.
Over the course of time coastal dunes may be impacted intense storm activity.
Recent work has suggested that coastal dunes tend to evolve toward a high or low morphology depending on the growth rate of dunes relative to storm frequency. During a storm event, dunes play a significant role in minimizing wave energy as it moves onshore. As a result, coastal dunes, especially those in the foredune area affected by a storm surge, will retreat or erode. To counteract the damage from tropical activity on coastal dunes, short term post-storm efforts can be made by individual agencies through fencing to help with sand accumulation.
How much a dune erodes during any storm surge is related to its location on the coastal shoreline and the profile of the beach during a particular season. During the summer a beach tends to take on more of a convex appearance due to gentler waves. Winter winds make a more of a concave appearance. As a result, coastal dunes erode quicker in the winter than in the summer. The opposite occurs in harsher summer weather.
Ecological succession on coastal dunes:
As a dune forms, plants thrive. Conditions on new dune are harsh, with salt spray from the sea carried on strong winds. The dune is well drained and often dry, and composed of calcium carbonate from seashells. Rotting seaweed, brought in by storm waves adds nutrients to allow pioneer species to colonize the dune. Sea grasses are well adapted to harsh conditions, typically having deep roots.