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supported by a wealth of research on barrier island communities spanning from the mid-
nineteenth century (Ehrenfeld 1990). The increased rate at which sea level rise is occurring,
however, differs greatly from historical measurements of “normal” rise (IPCC 2014).

Since the last glacial maximum 18,000 years ago and the ensuing (current) interglacial
period, sea level rise has caused barrier islands to generally retreat (Frankenburg 1997). Sand
naturally moves throughout the barrier island sand-sharing system—sometimes building up the
beach, sometimes decreasing the beach, and sometimes moving to adjacent barrier islands
(Pilkey 2007). The natural movement of sand is one of the problems associated with beach
development and during the development process, the sand-sharing system becomes disrupted
(Pilkey 2007). This natural movement of sand is termed “shoreline retreat.” Shoreline retreat
amplified by an increase in sea level rise is destined to become more impactful to coastal
communities over the short term (Pilkey 2007).
Changing Sands

Sand is not a stable beach commodity; it moves much like a body of water. In fact,
Pilkey (2007) compares sand transport to a river. As waves break on the beach, sand is both
deposited and removed through currents formed via wave energy (Pilkey 2007). By subtracting
the larger from the smaller, the net longshore sand transport volume is calculated. There exist
many variables that determine the net longshore sand transport volume. The distance from the
continental shelf, sand composition, wave intensities, wind, shoreline currents, tidal volumes,
geological components, and feedback are a few of the daily variables (Pilkey 2007). Overlain on
these everyday variables are the effects of storm activity. Storms have been documented to
remove large portions of the beach in a single episode (Pilkey 2007).

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