Narrow elongate deposits of sand situated
offshore and generally elongate parallel to the main shoreline.
They are typically only elevated slightly above high tide level
and separated from the mainland by a lagoon. Barrier islands
are slightly broader than barrier beaches and are typically a
few to several meters above sea level. Different geomorphic
zones in barrier island systems include the beachfront, sand
dunes, vegetated zones, and swampy terranes and a lagoon
separating it from the mainland. Barrier beaches and islands
often form chains of islands known as barrier chains, famous
examples of which are located on the southern side of Long
Island (New York), forming the Outer Banks of North and
South Carolina, and the Lido of Venice (Italy).
The sand that comprises barrier beaches and islands is
very mobile, being reworked by storms and waves that strike
the shore obliquely, transporting sand along the shore in a
process called longshore drift. Individual sand grains in the
beach swash and backwash zone may move as much as several
hundred meters in a single day. In such an environment,
the beach face is continually changing, with tidal inlets and
other beach features constantly appearing or disappearing.
Barrier beaches and islands are extremely sensitive environments
that can be easily destroyed or modified by human
activity disrupting the vegetation and sand surfaces of the different
geomorphic zones. Hurricanes and other storms can
also disrupt, totally rework, or even remove barrier beaches,
making them very hazardous places to live. The United
States’s most deadly natural disaster occurred in 1900 when a
hurricane hit Galveston, Texas, built on a barrier island.
Nearly 7,000 people died when a storm surge and high winds
flooded and demolished most of the city.
See also BEACH; HURRICANE.
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