Cialone, M.A., and Kraus, N.C. (2001). Engineering Study of Inlet Entrance Hydrodynamics: Grays
Harbor, Washington, USA. Proceedings of Coastal Dynamics 01, ASCE, Reston, VA, 413-422.
ENGINEERING STUDY OF INLET ENTRANCE HYDRODYNAMICS:
GRAYS HARBOR, WASHINGTON, USA
Abstract: An extensive field data collection effort was undertaken in Fall 1999
to examine wave propagation and currents through an inlet entrance. These data
support a circulation and wave model for Grays Harbor, Washington, a jettied
entrance with a large tidal prism. Both the field data and model results show
wave attenuation in the inlet entrance, flood currents strongest on the north side
of the inlet, and ebb currents more uniformly distributed. The influence of the
tidal current and water level on wave transformation was also examined. Ebb
current produces the greatest change at the inlet entrance, increasing wave
heights by as much as 0.5-1.5 m. Flood current increases wave height at the
seaward end of the entrance due to the ebb shoal redirecting flow offshore, but
reduces wave height in the inlet throat. Water level has a minimal impact on
wave height in the inlet entrance, but does control wave height in the back bay.
INTRODUCTION
Grays Harbor is one of the largest inlets in the United States with a spring tidal prism of
5.5 x 108 m3. Approximately 160 km2 of 240 km2 of bay area is emergent at low tide,
indicative of expansive tidal flats. The entrance channel is approximately 9-12 m deep
relative to mean lower low water, and the Federal navigation channel maintained on the
south side of the inlet entrance is 12-13 m deep. As part of a U.S. Army Corps of
Engineers (Corps) navigation study, data were collected at seven locations extending from
seaward of Grays Harbor and through the entrance to record surface wave propagation and
current through the inlet (Fig. 1). These measurements capture tidal flow and change of
water level by tide and wind, as well as wave diffraction into the bay, processes that
transport sediment into the navigation channel and over oyster-grounds leasing areas.
Numerical models of waves and currents have been established for the entrance and bay at
Grays Harbor as part of this study. This paper describes wave and current measurements
1) Research Hydraulic Engineer, U.S. Army Engineer Research and Development Center, Coastal
and Hydraulics Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199, TEL: (601) 634-
2139, FAX:(601) 634-4314, email:
2) Senior Scientist, Address the same.
Cialone & Kraus
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