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The Effect of Seawall Construction on the Coastline

The Effect of Seawall Construction on the Coastline. Ben McGinnis GLY 558 – Introduction to Coastal Management. Seawalls, Bulkheads, and Revetments. Seawalls are usually massive, vertical structures used to protect backshore areas from heavy wave action

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The Effect of Seawall Construction on the Coastline

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  1. The Effect of Seawall Construction on the Coastline Ben McGinnis GLY 558 – Introduction to Coastal Management

  2. Seawalls, Bulkheads, and Revetments • Seawallsare usually massive, vertical structures used to protect backshore areas from heavy wave action • Bulkheads are large vertical retaining walls used to reduce loss of land to the sea and to protect backshore areas from wave action • Revetments are shoreline structures generally sloped in such a way as to mimic the natural slope of the shoreline profile and dissipate wave energy as the wave is directed up the slope

  3. Why don’t they work? • Lacks the flexibility of a dune system • A change in beach slope is not allowed • Longshore currents scour sand from the base of the seawall • Loss of sand from reflected wave energy

  4. Wave Energy • Dissipates over the surface of a natural beach • Seawalls reflect wave energy • Reflected wave energy stirs up the sand and washes it out to sea

  5. Sandbridge Beach, Virginia • Bulkheading began around 1988 • Primarily Steel • Beach has narrowed and flattened • Rebuilt bulkheads • Old bulkheads in surfzone • Beach nourishment 1998 and 2002

  6. Interesting Pointsfrom: The Beaches are Moving: The Drowning of America’s ShorelineKaufman, W., and Pilkey, O.H., 1983 • No erosion problem exists on beaches until people build on them. • Anything built along the coast increases erosion rates due to the lack of flexibility in the beach system. • Once beach protection is started it’s can’t be stopped. • To “save” the beach, we must destroy it. • The cost to save property is greater than the value of the property.

  7. Seawalls are constructed to protect beachfront homes, but how can you have a beachfront home when there is no beach?

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