Coastal Sand-sharing System

The coast of Georgia is constantly changing, with sand and sediment being moved onto and off of beaches and marshes by wind, currents and wave action. This so-called sand-sharing system erodes sand from one point along the coast and redeposits it somewhere else. The predominant nearshore currents are from north to south, so usually sand is carried from north to south along the coast.

Sapelo Island is one of the few places on the East Coast of the U.S. where the sand-sharing system operates with minimal interference from human activity.  After a long period of accretion, Nannygoat Beach experienced several years of erosion during the 1990s, losing 10 meters or more of dunes.  This cycle of erosion and accretion is constantly active, with sand eroded from one area of beach by storm waves being deposited in offshore sandbars and gradually being washed back onto the beach to be trapped and held by dune vegetation, or being deposited in another place along the coast.  As evidenced by the accretion on the south end of Sapelo during the past 45 years, some of the sand is transported southward by the prevailing currents.

Fortunately, beach erosion on Sapelo is only a minor problem even when it does occur since there are no major structures near the beach.  Erosion of Sapelo beaches can be a more serious problem for animals that use the beaches as nesting areas and depend on access to stable beach areas near but above high tide to lay their eggs.  One cause of nesting failure is higher than normal tides which submerge or wash away birds’ eggs or erode the area where loggerhead turtles have nested.

How islands are formed
Island Sediments
Sapelo Island