Geoscience Reference
In-Depth Information
Barrier islands:
Moving ribbons of sand
islands and the Dutch and German Frisian
barrier islands, several villages coexist
with the national seashores, causing some
political discomfort. In 1972 the U.S. Park
Service made the startling announcement
that nature would be allowed to take its
course on the seashores. It was a pioneer-
ing recognition of the ultimate futility of
halting shoreline retreat in a time of rising
sea level. It was also a recognition of the
high environmental and economic cost of
the coastal engineering approach to hold-
ing shorelines in place.
Barrier island migration, now recognized
as a global phenomenon on coastal plain is-
lands, occurs as the ocean side retreats and
fans of storm overwash sand widen the
back side of the islands. The ocean side re-
treats as the back side advances into the la-
goon, and the whole island moves landward
and upward, out of the way of a rising sea.
Development on barrier islands of course
halts the migration process. Of particular
concern are high-rise buildings built adja-
cent to the eroding beach. In Florida there
are virtually hundreds of miles of such
high-rise-lined beaches, making impossible
a rational response to sea level rise, such as
moving back.
On most coastal plain islands, including
the Outer Banks, the Frisian Islands of the
Netherlands and Germany, and some of
the Algarve Islands of Portugal, where the
shoreline is not being held in place with en-
gineering structures, shoreline erosion is
occurring on both sides of the islands. The
thinning rate of the Outer Banks of North
the economic facts of life
Barrier islands make up about 12% of the
world's open ocean shorelines. They are a
particularly vulnerable coastal landform,
along with all kinds of sand spits and bay-
mouth bars, and since they are popular
sites for tourist development, their future
in a world of warming and of rising sea
level is of great concern. The greatest haz-
ard facing these islands is an economic one.
As the world's cities are increasingly threat-
ened by sea level rise, it is an economic and
political certainty that they will trump the
more lightly developed barrier islands for
funding. It also seems a certainty that the
long-range fate of most of these islands
must be abandonment. One exception may
be the Persian Gulf city of Abu Dhabi, a city
of one million inhabitants, the largest city
located almost entirely on a barrier island.
the outer banks
of north carolina
The Outer Banks of North Carolina on the
East Coast of the United States is a chain
of six barrier islands 210 kilometers (130
miles) long that extends from the Virginia
border to Beaufort Inlet, North Carolina.
The chain incorporates both Cape Hatteras
and Cape Lookout and the two national
seashores bearing their names.
As on the Portuguese Algarve barrier
