Geologic
History
The
island of Holden Beach has undergone considerable morphologic changes over
the past 150 years. In 1858, the beach was composed of two islands, Holden
Beach and Robison’s Beach, bisected by Bacon Inlet. This inlet remained
open until 1938, when littoral transport (sand movement by wave action)
eventually bridged the gap between the two communities. The remnant site
can be viewed near Swordfish St. on the western end of the island. Another
inlet also existed during this time period, known as Mary’s Inlet. This
inlet was closed by 1924. The modern day location of this inlet exists
around the development communities, located on Greensboro St.
These areas have extremely low elevations and are
very susceptible to overwash events during major storms. Dredging of the
Intracoastal Waterway around 1930 also affected the morphology of the
island. Prior to this time, livestock grazing on the island had
considerable impact on the vegetation. Once native vegetation was
reestablished, large dune features began to develop, as aeolian transport
reworked the available sand source. Large parabolic dunes continue to
develop in the western end of the island, and have encroached upon the
back barrier marsh system due to the high volume of sediment transported
alongshore.
This net transport of sand from the east to west
has resulted in a net accretion of almost 250 feet of beach in the west
end. The accretion is in the form of a recurved spit. This spit has
prograded down the island, altering the positioning of the navigational
channel, as well as the flow dynamics of Shallotte Inlet. |
Geology of island
Area of low elevation
Sand transport
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