To appear: Shore & Beach, Vol 72, No. 1, 2004.
inlet has been maintained by extensive dredging and other engineering activities
to keep it open for navigation (Headland et al. 1999).
Volume calculations of the Fire Island Inlet shoal features were based U.
S. Coast & Geodetic Survey bathymetric information from 1933 and 1950
available in digital format and from the 1996 SHOALS data. The cut and fill
areas based on a comparison of 1933 and 1996 surveys are shown in Figure 9.
Fire Island Inlet includes a large submerged ebb shoal system to the west of the
inlet entrance, and a main flood shoal to the east of the barrier overlap area. A
feature termed a secondary flood shoal is located within the inlet channel to the
south of Oak Beach.
Volume calculations indicate that the ebb shoal volume increased by 11.8
million cy between 1933 and 1996 (Figure 10). The majority of this increase
occurred between 1933 and 1950 when approximately 10 million cy of sand was
added to the ebb shoal (Figure 10). Over time, the entrance to Fire Island Inlet
has become increasingly filled with sediment, making navigation within the
channel difficult. In 1996, the ebb shoal volume was calculated at over 32 million
cy of sediment, enough to supply the western beaches with about a century's
worth of sand. The ebb shoal sediment volume did not dramatically increase
from 1950 to 1996, which may be explained by an increase in the occurrence of
storms within the area during that time and mining of approximately 5 million cy
of sand from the ebb shoal for nourishment of downdrift beaches (Figure 11,
Table 1).
The main flood shoal system to the east of the barrier overlap area
increased in volume by 3 million cy from 1933 to 1996. The primary flood shoal
does not contain as much sediment as the ebb shoal and was estimated in 1996
to contain approximately about 21.3 million cy of sand above a base elevation of
-29.5 ft NGVD. The flood shoal is also partially intertidal having elevations that
exceed mean low water along the rim of the fan-shaped subunits that form the
overall feature. Navigation through the inlet channel is somewhat restricted to
the south of Oak Beach due to the presence of the secondary flood shoal
accumulation within the inlet interior of the inlet. There has been little cutting or
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