Kiawah Island’s Dynamic Shoreline
Shaped by Waves, Tides, and Sand
By Leslie Reynolds Sautter, PhD, Department
of Geology and Environmental Geosciences,
College of Charleston
S
Figure 1: Much of Kiawah’s shoreline consists of a broad
beach with numerous small dunes and vegetated beach ridges.
(Image from A Coast for All Seasons, courtesy of M. Hayes
and J. Michel.)
Figure 2. Swash and backwash from breaking waves causes the
longshore transport of sand along the beach.
(Image from Keener-Chavis and Sautter, 2003).
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outh Carolina’s coast is home to numerous barrier
islands, many of which have extensive, broad, and
pristine sandy beaches with sea-oat covered dunes,
and lush maritime forests of live oak and Palmetto
trees. On their landward sides, tidal creeks meander through
the adjacent saltmarsh, flowing to the rhythmic ebbs and
flows of the tides. The central portion of our coast has a string
of these lovely, pearl-like barrier islands—from Seabrook
Island in the south to Bull Island in the north. Kiawah’s wide
beaches and multiple rows of forested beach ridges are the
result of a long history of the shoreline’s seaward growth
(Figure 1). Modern coastal processes have been modifying
Kiawah’s shape and geologic characteristics for several
millennia.
In general, a barrier island’s geologic shape, or
geomorphology is largely a function of three interacting
factors: 1) the energy of waves breaking on its shoreline, 2)
the local tidal range’s effect on energy within adjacent inlets,
and 3) the volume of sand available to naturally nourish
the beach. Along the South Carolina coast, where both tide
and wave energies are moderate, sand quantity is arguably
the most important factor of the trio. If an island lacks sand
supply, it will likely be in an erosional state, while an island
with abundant sand resources will potentially accrete, or
grow, through time.
Kiawah Island is a geologically thriving barrier island
and was used as a model by Dr. Miles O. Hayes (University
of South Carolina) for his classification of prograding
barrier islands. The term prograding refers to the shoreline’s
seaward growth as a result of long-term sand deposition and
accumulation. A prograding barrier island has abundant sand
Naturally Kiawah