GLOBAL WARMING, SEA LEVEL RISE,
AND BEACH RESTORATION
There have been many ice ages in earth's history. When they come to an end, vast deposits of
melting ice cause sea levels to rise rapidly. Ocean beaches and barrier islands are flooded and
submerged during periods of rapid glacial melt-off.
Between ice ages, once the melt-off is largely complete, sea level becomes relatively stable, rising
or falling over thousands of years at moderate rates. During these "moderate" interglacial periods,
factors other than changing sea level may dictate trends in coastal sedimentation.
The last ice age ended about 17,000 years ago. During the past 5000 years, sea level rise has
moderated. During this era (late Holocene) beaches and barrier islands have not retreated, a
popular misconception, rather they have increased in mass and expanded seaward because sand
supply to beaches has exceeded the effects of sea level rise.
Scientists know shorelines have been expanding seaward in the present geological era because a
beach ridge plain is left behind as shorelines prograde. Growth ridges spreading across barrier
islands are analyzed in a manner not unlike growth rings in trees. They tell a straightforward story.
Barrier islands germinated out of the sea about 4000 years ago and grew steadily seaward until
recently reversed.
It is unlikey that the sudden end of the "beach building" era was a natural occurrence. The reversal
of coastal progradation neatly corresponds to the onset of widespread coastal engineering activity
related to navigation. In all probability, beaches and barrier islands should still be expanding today.
Because beaches are complex, non-linear systems, they display what scientists call "sensitive
dependence." Simply put, this means that even very small changes to a non-linear system will have
counter-intuitively large effects on that system. The widespread introduction of dredged navigation
channels has had a profoundly erosive effect on the world's coastlines according to most
independent coastal experts.
(See
Primary Causes of Erosion.)
In addition to dredged navigation channels, factors contributing to unnatural coastal erosion include
the damming of rivers (which cuts the flow of sediment to the coast) and mining rivers and beaches
for construction sands. In some cases, building too close to the shoreline has instigated problems,
though this is usually an irritant to an erosion problem caused by other factors.
(see
Dr. Pilkey vs. The Army Corps of Engineers.)
Sand Management
If sea level rise accelerates in response to global warming, conventional beach restoration
programs become increasingly futile. A new management technique, "sand banking," may be used
to reverse unnatural patterns of coastal retreat.
The beach system's natural ability to prograde is reactivated by technical advances which boost the
efficiency of the beach profile to gather and hold sand in the nearshore. The natural ability of
beaches to act as self-adjusting buffers in the face of rising sea levels is reestablished.
Beach growth has been induced by Undercurrent Stabilizer Technology even in the most adverse
conditions - critically eroding shorelines adjacent to federal navigation channels during rapidly rising
water levels (of a foot or more per year) on the storm-plagued Great Lakes. Beneficial shoaling is
widespread without the undesirable side effects and continual maintenance normally associated
with conventional programs.
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