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Coastal processes interact with the local coastal geology and sediment supply to form and modify a coastline's physical features – barrier islands, beaches, dunes, bluffs, and upland areas. To understand the nature of barrier islands and their beaches, it is important for the decision-maker to have a general knowledge of the geology of the areas forming these environments. The extensive barrier island systems along the Atlantic and Gulf Coasts of the United States are found primarily adjacent to a coastal plain geologic system. Many of the barrier islands of the north Atlantic have developed along glacial coasts having a wide range of geology found beneath the glacially derived sediments.

Primary functions:

• to provide protection to backshore property
• to increase the recreational space along the shore
• May replicate natural coastal processes by augmenting coastal sand budgets
• Sediment texture (grain size and sorting) is critical for success. Sand fill must be compatible with native beach sand.

Environmental issues:

• dredging may cause short-term direct mortality to sessile organisms, modifies seafloor habitats and sedimentary character
• burial of plants and organisms (SAV, shellfish)
• blockage of light in water (coral reefs, SAV)
• toxicity of sediments
• dredging too close to shore can cause erosion
• changes critical habitat for nesting sea turtles and birds
• provides a false sense of security that increase development pressure

Assessing beach erosion

There are two different ways that a sandy beach can become eroded. The first type of erosion is the natural response of a beach to storms and calm weather. During storms, sand from the visible beach submerges below the water to form storm bars that protect the beach from further damage. During calm weather smaller waves return sand from the storm bar back onto the visible recreational beach surface in a process called accretion. The term 'erosion' always sounds bad and conjours up the idea of environmental damage so the term submersion is often used for the natural erosion processes of a healthy sandy beach to distinguish this process from the more serious type of erosion described below.

Another type of erosion is a more serious problem for beach health. Some beaches do not have enough sand available to coastal processes to respond naturally to storms. Reasons can include:

• a seawall locking up sand dunes under urban areas or
• coastal structures like Ports and Harbours that prevent longshore drift
• river management structures like dams
• some coastlines are naturally eroding due to processes like continental drift
• climate change impacts like sea level rise, increased storminess or changes to the pattern of ocean currents

When there is not enough sand left available on a beach, then there is no recovery of the beach following storms.

The submersion/erosion distinction between total sand in a beach (erosion scale) and its position above or below the waterline (submersion) - is an important aspect when considering beach nourishment proposals. The response to coastal erosion should be different between a situation of extreme erosion and one of extreme submersion - even though the visible portion of the beach erosion will appear the same to observers. An eroded beach in a healthy environment may fully recover with no assistance through beach nourishment. There are beaches that are eroding due to natural processes like longshore drift but the majority of problems for beach health are anthropogenic. Addressing the anthropogenic cause of the beach erosion problem is often a better response to beach erosion than beach nourishment.

Beach nourishment projects

Beach nourishment projects are usually constructed along shorelines where an erosional trend is present that could be either natural or a result of human activities. In those cases where this trend is due to human activities, the project will perform much better if the cause of the erosional trend can be minimized or eliminated in conjunction with construction of the beach nourishment project. The setting of a beach nourishment project is key to design and potential performance. Possible settings include a long straight beach, a project adjacent to an inlet that may be either a natural or modified inlet and a pocket beach. Projects constructed on rocky or seawalled shorelines, that otherwise have no sediment, present unique problems.

View the Beach Nourishment Process Interactive Animation
Read more about how Beach Nourishment projects work

Questions concerning Programs & Projects?

Email point of contact for Charleston's Programs & Projects Division

Mailing Address:
US Army Corps of Engineers
Programs & Projects Division
69A Hagood Ave.
Charleston, South Carolina 29403-5107