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

(6-5)

where *V*E = volume of the ebb shoal in cu yd, and *P *= tidal prism in cu ft. The

value of the empirical coefficient *C*E depends on wave exposure as *C*E = 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.

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:

(6-6)

where *V*FT = 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:

(6-7)

where *A*FT = 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:

(6-8)

where *V*FN = 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:

(6-9)

270

Chapter 6 Inlet Morphology and Stability

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