Hurricane Sandy, considered to be the worst storm since 1938, hit Fire Island New York, the sand-ridged barrier island playground east of New York City, in October of 2012.
Ten months later, the USGS released a detailed report of the damage. The beaches, visited by over 800 000 every summer, had lost over half their volume and the dunes had overwash along almost half of the island.
Efforts are been made to rebuild this 31 mile long car-free community of 500+ population that once included Lee Strasberg, according to Jane L. Rosen: “When Marilyn Monroe visited Lee Strasberg on Fire Island for the very first time, she said, ‘What a lovely place this is — it’s got water all around it’.” But, as the USGS advises, “storms like Sandy are part of the natural evolution of barrier islands, which ultimately result in islands that are more resilient to sea level rise.”
What Creates Barrier Islands?
As defined by William K. Smith et al, coastal barrier islands are “unique ecosystems that border coastal shorelines and physically separate the offshore oceanic province from inshore wetlands, bays, sounds, and estuaries. As their name implies, they form a protective barrier between continental shorelines and the powerful wave action that originates offshore.”
There are three prevailing theories for the origins of barrier islands:
- The classical theory that barrier islands are formed from offshore bars.
- The spit accretion theory that barrier sediments come from longshore sources; and
- The submergence theory that coastal ridges are separated from the mainland, forming lagoons behind the ridges
In a report by Scott A. Mandia, on the effects of the 1938 hurricane on the Long Island barrier islands, much emphasis was placed on longshore drift, defined by W. G. Moore as, “the movement of shingle and sand along seashores due to the waves advancing obliquely up the beach.”
Whatever the theory, it appears that barrier island systems have four elements in common:
- They develop most easily on wave dominated coasts with a small to moderate tidal range;
- There must be a relatively low gradient shelf;
- There must be an ample sediment supply; and
- There must be a stable sea level.
What is the Function of Barrier Islands?
Barrier islands protect and enhance the coast. As William K Smith et al explain, the islands provide “critical ecosystem services to the heavily populated coastal regions of the world,” including:
- Substantially reducing damage from extreme episodic events such as hurricanes and tsunamis; and
- Providing a prime attraction for human development.