Fig. 2. Idealized inlet bathymetry to approximate conditions at Shinnecock Inlet, NY
Fig. 3. ADCIRC and STWAVE domains for idealized inlet model simulations
and without the influence of tidal currents to examine modification of waves by currents.
Discussion focuses on the current generated for the largest modeled storm waves (4 m,
12 sec). Normal and obliquely incident waves are considered in the discussion. The ocean
boundary of the circulation model was forced with a sinusoidal time series to represent a
tide with a 1.5-m range and 12.42-hr period. The model simulation period was 1 day. The
wave model simulations were made every 3 hr, and radiation stress gradients were spatially
interpolated from the STWAVE domain to the ADCIRC domain. Beyond the wave model
domain, radiation stress gradients were extrapolated to zero using a standard sigmoidal
function. Radiation stress gradients were then temporally interpolated for every ADCIRC
timestep.
Figs. 4a and 5a show circulation model results at peak flood and peak ebb, respectively,
with no wave coupling (tidal currents only). Flood currents increase on approach to the
inlet throat (constriction), reaching a maximum speed of about 0.8 m/sec. Ebb currents
behave similarly, with maximum currents speeds in the inlet throat (0.8 m/sec) and
diminishing current speeds upon exiting the inlet.
Figs. 4b and 5b show calculated current patterns at peak flood and peak ebb,
respectively, with the inclusion of wave-induced currents generated by 4-m, 12-sec
normally incident waves. Fig. 4b shows strong (1.8 m/sec) currents on the ebb shoal
caused by large gradients in radiation stress (breaking waves) in this region. Large gyres
are observed on both sides of the ebb shoal location caused by lateral gradients in radiation
stress (refraction) combined with the tidal currents. Currents in the inlet throat are
strongest along the "side walls" of the inlet. Fig. 5b (ebb condition) also shows strong
currents (1.5 m/sec) on the ebb shoal caused by breaking waves. In this case, the
interaction of waves with an opposing current causes a strong (1.3 m/sec) longshore current
to the left and right directions.
Cialone, Militello, Brown, and Kraus
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