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
• 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
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
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
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
Interesting Points
from: The Beaches are Moving: The Drowning of America’s Shoreline
Kaufman, W., and Pilkey, O.H., 1983
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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.
Seawalls are constructed to
protect beachfront homes, but
how can you have a beachfront
home when there is no beach?