Geomorphology
Ebb Shoal of Original Inlet. Soon after the original inlet was closed, the old ebb tidal shoal
began to move onto the shoreline fronting the old inlet area. Subsequently, a long tidal pool
formed as the seaward margin of the shoal attached to the downdrift shoreline and remained
intact from June through October 2002. The newly formed tidal pool afforded beach users a
wonderful place to play and swim, with many people visiting to enjoy the pool. By late
November 2002, this sand body had been redistributed by waves and currents, shifting primarily
north with no bulge or other evidence of the original ebb tidal shoal.
The collapse of the ebb shoal at the original inlet entrance is of theoretical interest and was
captured quantitatively in monitoring surveys (Fig. 10). Assuming that the bathymetry did not
change substantially from the December 2001 survey until closing of the original inlet in early
March 2002, the October 2002 survey allows a 6-month post-closing estimate of volume change
to be measured. In Fig. 10, the volume change within above the 1-m contour was 130,000 m3,
with most of this sand reaching shore soon after the closing to form the long tidal pool.
December 2001 to October 2002
Difference, ft, NGVD 29
-7.72 - -5
-5 - -3
-3 - -1
-1 - 0
0-1
1-3
N
3-5
5-7
7-9
9 - 11
11 - 13
13 - 15
15 - 17.282
0
1000 Feet
Fig. 10. Bathymetry change at original inlet, December 2001 to October 2002 (6 months
post inlet closing).
Ebb Shoal of New Inlet. According to a predictive relation of Walton and Adams (1976), based
on the calculated tidal prism the volume of the ebb shoal is expected to reach 0.9 to 1.2 x 106 m3
(1.2 to 1.6x106 yd3), at which time natural sand bypassing would be fully established. The
monitoring program intends to capture growth of the ebb shoal. The 6-month post-inlet opening
survey (difference shown in Fig. 11) gave a gain of 160,000 m3 (212,000 yd3) above the .03-m
11
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