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F.S. Buonaiuto, N.C. Kraus / Coastal Engineering 48 (2003) 5165
through relatively narrow entrances maintain steeper
the ebb shoal was again dredged in August 1997, and
slopes on the order of 6j were observed 3 months
channel slopes than the unstabilized inlets (New Pass
and Perdido Pass, Table 3). Stabilization of an inlet
later during the November survey. Slopes of the relict
south-facing channel were greatest (2j) where it
with jetties confines the ebb-tidal jet and increases
scour in the channel, whereas ebb flow at non-jettied
intersected the newly dredged channel. Maximum
inlets spreads through a larger cross-section, tending
slopes along the seaward portion of the relict channel
were 0.5j. The deflation of the relict channel walls
to smooth the bottom and creating favorable condi-
tions for multiple shallow entrance channels. Al-
on the outer shoal suggests that infilling processes are
though Moriches and Shinnecock Inlets receive
wave dominated and operate on those regions of the
significant wave forcing, wave action is not believed
relict channel that experience the strongest wave
to control the slopes of the channel walls. In contrast,
forcing. By April 1998, the relict channel had filled
in areas where wave action dominates transport by
with sand, and overlying bar features appeared to
tidal currents, both inlets have steep slopes along the
control the slopes along the down-drift portion of the
ebb shoal, bypassing bar, and the attachment bar (Fig.
ebb shoal. The seaward-most section of the main
7)--morphologic features forming the inlet sand
navigation channel showed signs of reworking as side
slopes there decreased from 4j to 2j during the 8-
bypassing system (Kraus, 2000). The other inlets
surveyed by the SHOALS system experience milder
month interval after dredging.
wave conditions than Shinnecock and Moriches
Four of the SHOALS-surveyed inlets (Shinnecock,
Inlets, and these inlets exhibit more gently sloping
Moriches, New Pass, and Lake Worth) showed asym-
ebb shoals and bypassing bars. Slopes along the
metries in side slopes of their cross-channel profiles.
down-drift attachment bars ranged from 1j to 4j for
Near the throat, the asymmetries associated with
higher wave-energy inlets and 1j to 2j for lower
steeper, up-drift channel slopes appear to be related
wave regimes. Bar slopes become steeper as one
to the encroachment by submerged spits or migrating
shoals having slopes ranging from 1j to 3j. However,
moves from the attachment bar to the main ebb shoal.
Dredging alters the side slopes of channels. The
on the outer shoal the asymmetry in channel side
slope, which may be on the order of 2 3j, will shift
entrance channel at New Pass was realigned perpen-
dicular to the shoreline in 1991, and immediately
from up- to down-drift sides of the channel depending
began migrating to the down-drift southerly orienta-
on the orientation of the channel.
tion (McClung and Douglass, 1999). In 1994, chan-
The Great Lakes sites are representative of a differ-
nel slopes at New Pass were on the order of 3 5j,
ent hydrodynamic regime, selected to provide the
and subsequent surveys showed that these slopes
extreme situation of no tide. Without tide, the location
decreased by 0.5 1j/year. By 1996, the maximum
of the surf zone varies through a smaller range, and
slope in the southward migrating channel was about
waves break in a more confined area. Although some
3j. The initial realigned navigation channel through
seiching occurs on the Great Lakes, morphology at its
harbor entrances is predominantly controlled by
waves, as evidenced by a continuous longshore bar
observed in the data sets. Slopes along bar complexes
at Great Lakes harbor entrances were substantially
larger than at tidal coasts, ranging from 4j to 6j. In
several locations slopes reached maximum values of
8 10j.
3.2. Depth over crest of ebb shoal
The bathymetric data enabled identification of
ebb-shoal crests at all the inlets. The crest is defined
as the shallowest water located directly seaward of
the main ebb channel (Fig. 5). The shoal depth was
Fig. 7. Definition sketch for inlet morphology.
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