Impacts to the Beach from Seawalls
- Passive erosion -"Wherever a hard structure is
built along a shoreline undergoing long-term
net erosion, the shoreline will eventually migrate
landward beyond the structure. The effect of
this migration will be the gradual loss of beach
in front of the seawall or revetment as the water
deepens and the shoreface moves landward....
While private structures may be temporarily saved,
the public beach is lost. This process of passive
erosion appears to be a generally agreed upon
result of fixing the position of the shoreline
on an otherwise eroding stretch of coast, and
is independent of the type of seawall constructed."
It is evident that passive erosion will eventually
destroy the recreational beach area unless this
area is continually replenished. Excessive passive
erosion may impact the beach profile such that
shallow areas required to create breaking waves
for surfing are lost.
- Placement loss - Seawalls are placed on the beach.
In many cases, construction of seawalls is on
the beach, which is public property. This is
a taking of extremely valuable public property.
- Active Erosion - Refers to the interrelationship
between wall and beach whereby due to wave reflection,
storm surf zone narrowing and a thousand other
processes the wall may actually increase the
rate of loss of beach. This is site specific
and dependent on sand input. There are varying
opinions on if this effect actually exists. However,
as watchdogs of the coast, until there is overwhelming
evidence that this effect is not significant,
this represents yet another reason to avoid constructing
seawalls.
- Public access impacts - these can be a result
of passive erosion, placement loss or active
erosion. Seawalls built on eroding beaches, will
lead to the loss of access. Most beaches in Rincón
are undergoing erosion.
- Visual/aesthetic impacts - Seawalls are ugly
and detract from simple pleasures as a walk on
the beach.
- Economic issues - local, state or federal subsidies
or construction to protect private property,
or insurance coverage. Construction is performed
on State or Municipal land. The public has never
been compensated for this loss of valuable property.
- Loss of sand supplied by the eroding coastline
that is armored. This is sand that is lost from
the system because seawalls prevent the naturally
occurring erosion to supply additional sand to
beaches. This natural erosion also creates additional
space for the beach to stay wide.
- The most important thing to remember is that
a seawall is never built to protect the beach.
Rather, it is built to protect property, structures
or a cliff from erosion.
More information on Seawalls:
Click
here to see information from the Surfrider Foundation's
State of the Beach report.
Click
here for Rod's page full of links to useful information
on Puerto Rico's coastline.
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