Inlet Entrance Hydrodynamics, Grays Harbor,
Washington
Mary A. Cialone1 and Nicholas C. Kraus2
Abstract
is 12-13 m deep. As part of a U.S.
mid-September to mid-November
Army Corps of Engineers navigation
1999 spanned two lunar months
study, data were collected at seven
(Hericks and Simpson 2000).
An extensive field data collection
locations extending from seaward of
effort was undertaken during the fall
The tripods were deployed along
Grays Harbor and through the
of 1999 to examine wave propaga-
or near the navigation channel
entrance to record surface wave
tion and currents through an inlet
(Figure 1). Stations 1 through 6
propagation and current through the
entrance. These data support a cir-
extend from the entrance, through
inlet (Figure 1). These measure-
culation and wave model for Grays
the inlet, and into the bay. Each
ments capture tidal flow and change
Harbor, WA, a jettied entrance with
tripod was configured with a SonTek
of water level by tide and wind, as
a large tidal prism. Both the field
Hydra, functioning as a directional
well as wave diffraction into the bay,
data and model results show wave
wave gauge and an up-looking
processes that transport sediment
attenuation in the inlet entrance,
1,500-kHz Acoustic-Doppler Profiler
into the navigation channel and over
flood currents strongest on the north
(Figure 2). The Hydras contained a
oyster-grounds leasing areas.
side of the inlet, and ebb currents
down-looking Acoustic-Doppler
Numerical models of waves and cur-
more uniformly distributed. The influ-
Velocimeter Ocean Probe, a
rents have been established for the
ence of the tidal current and water
high-resolution Resonant Pressure
entrance and bay at Grays Harbor
level on wave transformation was
Transducer, and two optical
as part of this study. This paper
also examined. Ebb current pro-
backscatterence sensors. This
describes wave and current mea-
duces the greatest change at the
instrument suite documented the
surements and model simulations
inlet entrance, increasing wave
waves, current near the bottom, and
conducted to examine surface wave
heights by as much as 0.5-1.5 m.
water level; the current through the
propagation through the inlet, includ-
Flood current increases wave height
water column in 0.5-m bins; and the
ing the modification of the waves by
at the seaward end of the entrance
suspended-sediment concentration
the tidal current and water level.
due to the ebb shoal redirecting flow
through the inlet entrance. Station 0
offshore, but reduces wave height in
(the seaward-most location) was
the inlet throat. Water level has a
configured with an Ocean Probe and
Field Data Collection
minimal impact on wave height in
an RDI Sentinel ADCP with direc-
the inlet entrance, but does control
tional wave-spectra firmware to
wave height in the back bay.
The data-collection program con-
determine if comparable data are
sisted of bathymetry surveys in the
derived from the two different mea-
offshore and along maintained and
surement methods.
Introduction
natural channels; a Light Detection
and Ranging (LIDAR) survey and
Numerical Simulations
Grays Harbor is one of the larg-
controlled aerial photography of land
est inlets in the United States with a
and tidal flats during lower tide in
spring tidal prism of 5.5 x 108 m3.
the bay; measurement of water level
The field-data collection supports
Approximately 160 km2 of 240 km2
at five locations around the bay
both circulation and wave numerical
of bay area is emergent at low tide,
periphery, wind and barometric pres-
models for Grays Harbor. The
indicative of expansive tidal flats.
sure at a nearshore tower; and
ADvanced CIRCulation (ADCIRC)
The entrance channel is approxi-
waves, water level, tidal current
long-wave hydrodynamic model can
mately 9-12 m deep relative to mean
through the water column, and sus-
define the circulation and water level
lower low water, and the Federal
pended sediment concentration at
associated with both tide and wind
navigation channel maintained on
seven bottom-residing tripods. The
(Luettich, Westerink, and Scheffner
the south side of the inlet entrance
tripod deployment interval of
1992). A two-dimensional
Research Hydraulic Engineer, U.S. Army Engineer Research and Development Center, Coastal and
1
Hydraulics Laboratory, 3909 Halls Ferry Road, Vicksburg, MS
Senior Scientist, U.S. Army Engineer Research and Development Center, Coastal and Hydraulics
2
Laboratory, 3909 Halls Ferry Road, Vicksburg, MS
27
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