Ebb shoal volume
Walton and Adams (1976) derived empirical equations based on analysis of
42 inlets that relate the volume of the ebb shoal of a mature or equilibrium inlet
to its tidal prism. This relation can be expressed as
VE = CE P 1.23
(6-5)
where VE = volume of the ebb shoal in cu yd, and P = tidal prism in cu ft. The
value of the empirical coefficient CE depends on wave exposure as CE = 8.7 10-
for highly exposed coasts (typically, Pacific Ocean coast), 10.5 10-5 for
5
moderately exposed coasts (typically, northern Atlantic Ocean coast), 13.8 10-5
for mildly exposed coasts (typically, Gulf of Mexico and southern Atlantic
coast), and 10.7 10-5 for all coasts.
Flood shoal volume
Carr de Betts (1999) derived empirical predictive relations that relate the
volume and area of the flood shoal of an inlet to its spring tidal prism. She
studied 61 inlets in Florida, 19 of them located along the Atlantic coast and 42
along the Gulf of Mexico coast. It is noted here that inlets of Florida lie on
coasts containing abundant quantities of fine sand (and small shell fragments in
the case of the gulf coast of Florida). Flood shoals would be expected to more
easily form in coastal environments with plentiful fine material, in contrast to the
coarser sediments found along the north shore of Long Island, NY.
Predictive expressions were developed for the near field (that part of the
flood shoal readily visible), far field (that part spread in a thin layer further in the
bay), and total flood shoal combining the near and far fields (Carr de Betts 1999).
The predictive relation between inlet tidal prism and total volume of the flood
shoal is:
VFT = 2.0389 x 104 P 0.296
(6-6)
where VFT = total volume of the total flood shoal in cu m, and P = the tidal prism
in cubic meters. The predictive relation between inlet tidal prism and total area
of the associated flood shoal is:
AFT = 4.7585 x 104 P 0.249
(6-7)
where AFT = total area of the flood shoal in square meters.
The predictive relationships between the tidal prism and the near field flood shoal
volume and area is used to estimate flood shoal area and volume at Mattituck
Inlet and Goldsmith Inlet later in this chapter. The predictive relationships
between the tidal prism and the far field flood shoal volume and area is not used
and is not shown here. The predictive relation between inlet tidal prism and near
field volume of the flood shoal is:
VFN = 4.056 103 P 0.314
(6-8)
where VFN = near field volume of the flood shoal in cu m, and P = the tidal prism
in cubic meters. The predictive relation between inlet tidal prism and near field
area of the associated flood shoal is:
AFN = 1.4532 x 104 P 0.254
(6-9)
270
Chapter 6 Inlet Morphology and Stability
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