and coarse-grained sediment component at these inlets that will minimize tidal
bypassing, and these inlets do not possess an ebb shoal because of the large grain
size of the sediment, weak wave action, and weak ebb discharges.
Mattituck Inlet
6
Goldsmith Inlet
on
ed
ati
at
5
orm
in
rf
)
m
rrie
low
Do )
(
high
ba
ted
of
ide (
it
na
mi
lim
4
T
.
ox
o
gy
D Appr
ner ed)
dE
e
t
Tid
ixe mina
M do
3
e
(tid
nergy
ixed E nated)
M
domi
wave
2
(
ated
Wave Domin
1
0
0
1
2
Mean Wave Height, m
Figure 6-1. Classification of tidal inlet morphology (after Davis and Hayes 1984)
Sand bypassing at tide-dominated inlets can also occur by breaching and
reconfiguring of the ebb shoal as the outer inlet channel meanders. This process
pertains to inlets without stabilization structures. Breaching and reconfiguration
combined with wave-driven onshore migration of sand bodies in the form of
swash bars can result in large volumes of sand bypassed from the ebb shoal to the
adjacent beaches (FitzGerald et al. 2000). In this process, the channel elongates
while typically migrating downdrift. Hydraulic friction of the long channel
reduces the inlet current that acts to maintain the inlet entrance; eventually,
sediment brought to the entrance by waves closes it. The blocked flow will then
break through at a narrow point in the spit located closer to the main channel
prior to migration, thereby starting a possible repeat of the cycle of migration,
closure, and reopening. This cyclic process may have acted at both Mattituck
Inlet and Goldsmith Inlet prior to their stabilization. It probably could not occur
at the present Goldsmith Inlet because of the wide beach segment located to the
west, adjacent to the jetty.
In contrast, wave-dominated inlets have small ebb shoals that are submerged,
and well-developed flood shoals that can be emergent at low tide. Natural sand
bypassing occurs through "bar bypassing," the mechanism of wave-driven
transport across the outer bar of the ebb shoal to downdrift bypass and
attachment bars. The typical morphology of the ebb shoal of an inlet has been
identified as an ebb shoal proper, which lies directly in front of the inlet, close to
266
Chapter 6 Inlet Morphology and Stability
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