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Fig. 12.3 Bedform patterns at New Inlet along the wave-dominated outer coast of Cape Cod, Massachusetts. Note the variety of
bedform heights, lengths, and orientations, which is a refl ection of fl ow velocity asymmetry and mutual evasive tidal channels
scour sand from the inlet channel and therefore they
maintain a larger throat cross section than would be
predicted by the O'Brien Relationship. Thus, Jarrett
( 1976 ) has improved the tidal prism - inlet cross-
sectional area regression equation for U.S. inlets by
taking into account wave energy and separating into three
classes the low energy Gulf Coast inlets, moderate
energy East Coast inlets, and higher energy West Coast
inlets. Even better correlations are achieved when engi-
neered inlets are differentiated from natural systems.
end members. Waves are responsible for transporting
sand back onshore, thereby reducing the volume of the
ebb-tidal delta. Therefore, for a given tidal prism, ebb-
tidal deltas in higher wave energy regimes contain less
sand than their counterparts along low wave energy
coasts. Although the Walton and Adams Relationship
works well for inlets all over the world, fi eld studies
have shown that the volume of sand comprising ebb-
tidal deltas can change through time due to the effects
of storms or processes of inlet sediment bypassing, and
these effects can change the shoal volume by more
than 10% (FitzGerald et al. 1984 , Gaudiano and Kana
2001 ).
A
=××
3.04
10
5
P
1.05
(12.1)
12.4.2 Ebb-Tidal Delta Volume - Tidal
Prism Relationship
=××
5
.1.23
V
1.89
10
P
(12.2)
12.5
Sand Transport Patterns
Walton and Adams ( 1976 ) showed that the volume of
sand contained in ebb-tidal deltas (V) is closely related
to tidal prism (P) by the relationship given in Eq. 12.2 .
This correlation is improved slightly when wave energy
is taken into account in a manner similar to Jarrett's
The movement of sand at a tidal inlet is complex due
to reversing tidal currents, effects of storms, and inter-
action with the longshore transport system. The inlet
 
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