Wave-current interaction in Willapa Bay

Abstract

[1] This paper describes the importance of wave-current interaction in an inlet-estuary system. The three-dimensional, fully coupled, Coupled Ocean-Atmosphere-WaveSediment Transport (COAWST) modeling system was applied in Willapa Bay (Washington State) from 22 to 29 October 1998 that included a large storm event. To represent the interaction between waves and currents, the vortex-force method was used. Model results were compared with water elevations, currents, and wave measurements obtained by the U.S. Army Corp of Engineers. In general, a good agreement between field data and computed results was achieved, although some discrepancies were also observed in regard to wave peak directions in the most upstream station. Several numerical experiments that considered different forcing terms were run in order to identify the effects of each wind, tide, and wave-current interaction process. Comparison of the horizontal momentum balances results identified that wave-breaking-induced acceleration is one of the leading terms in the inlet area. The enhancement of the apparent bed roughness caused by waves also affected the values and distribution of the bottom shear stress. The pressure gradient showed significant changes with respect to the pure tidal case. During storm conditions the momentum balance in the inlet shares the characteristics of tidal-dominated and wave-dominated surf zone environments. The changes in the momentum balance caused by waves were manifested both in water level and current variations. The most relevant effect on hydrodynamics was a wave-induced setup in the inner part of the estuary.

Hydrodynamics of a multiple tidal inlet system : Katama Bay, Martha�s Vineyard, MA

“…During Hurricane Irene (Aug 28) incident significant wave heights were greater than 5 m, and the model predictions of bay water levels are more accurate when wave forcing is included (Figure 2-5B). Unlike previous numerical results [Dodet et al (2013); Olabarrieta et al (2011)], the increase in the bay water level owing to wave forcing is relatively small, as discussed below, likely because water flows out of the bay into Vineyard Sound through Edgartown Channel rather than accumulating in a closed basin.…”

“…Nonlinear-advective terms, to a first order approximation, are assumed to cancel [Jay (1991); Olabarrieta et al (2011)] or to be small [Lentz et al (1999)]. Given the small spatial scales, Coriolis terms are small.…”

“…Thus, the dominant terms in the momentum balance are the pressure gradients between the sound, ocean, and bay, wave radiation stresses acting on Katama Inlet, and bottom stress owing to friction of the flows in the inlet channels. Although the one-dimensional model used here is sufficient to address the hypothesis [Bertin et al (2009);Dodet et al (2013); Malhadas et al (2009);Olabarrieta et al (2011)] that wave forcing is important to inlet currents (Figs. 2-5 and 2-6), a more sophisticated model [Hench and Luettich (2003); Olabarrieta et al (2011);Wheless and Valle-Levinson (1996)] might produce more detailed results.…”

“…Although the one-dimensional model used here is sufficient to address the hypothesis [Bertin et al (2009);Dodet et al (2013); Malhadas et al (2009);Olabarrieta et al (2011)] that wave forcing is important to inlet currents (Figs. 2-5 and 2-6), a more sophisticated model [Hench and Luettich (2003); Olabarrieta et al (2011);Wheless and Valle-Levinson (1996)] might produce more detailed results. For example, the model used here assumes that the water level in the bay responds uniformly to the forcing at the two inlets, and that the measurements at location 05 represent the bay water levels.…”

Field observations and numerical model simulations of a migrating inlet system

“…There have been many investigations of current-induced wave height growth or decay, usually for the case of currents flowing in the same or opposite direction of the waves [Gonzales, 1984;Jonsson, 1990;Wolf and Prandle, 1999;Olabarrieta et al, 2011Olabarrieta et al, , 2014and many others]. There are fewer observational studies of the current-induced changes in wave direction, partially because waves propagating into an opposing or following current ( = 0°or180°), such as commonly occurs near strong jets from inlets, river mouths, and estuaries, do not change direction (Eq 3).…”