Coastal Defenses
Coastal defenses
are objects and
engineering
techniques used to defend
coasts
against
erosion
and
flooding
. These may be hard engineering or soft engineering. Hard engineering techniques involve building
rock
or
concrete
structures, most commonly
sea walls
,
rock islands
,
rock aprons
and
breakwaters
. Piles of large rocks are especially efficient at dissipating wave energy as they are able to move, and water can
percolate
through them. Soft engineering most commonly involves encouraging the build up of land between the sea and the object being protected, most commonly a
beach
, but sometimes a
salt marsh
or
dune
system.
Beach nourishment
takes place at many coastal towns in western countries. Many places encourage
sediment
accumulation by constructing
groynes
, out of rock or concrete. These cause
sand
carried by
longshore drift
and sea
currents
to be
deposited
.
Vegetation
can also be grown on the
coasts
to stabilize the sand and reduce the effects of
erosion
. The alternative to coastal defenses is
managed retreat
.
See also
:
list of coastal topics
,
geography
,
earth science
.
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