digital bathymetry (used to define offshore and bay bathymetry) and shorelines.
The north jetty at Ponce Inlet is represented in the model as a series of land cells.
The jetty is specified as being three grid cells wide, which is wider than the real
structure. Three cells are required to block wave energy from propagating
through the structure. Future upgrades to the model will provide the capability to
represent structure widths that are less than the grid cell spacing.
Incident wave spectrum. The incident wave spectrum for Ponce Inlet was
generated using a TMA spectral shape (with a spectral peakedness parameter, γ =
5.0), cosnnα directional distribution (with nn = 12), Hmo = 5.2 m, Tp = 12.8 sec,
and αm = -7 deg (see Table 1 for guidance on spectra shape and directional
spreading parameters). These incident conditions represent extreme high wave
conditions measured at Ponce Inlet in March 1996.
Current field. The current field for Ponce Inlet was generated using the
tidal circulation model ADCIRC (Luettich, Westerink, and Scheffner 1992). The
current field output from ADCIRC was interpolated onto the STWAVE grid
using SMS. The current field is plotted in Figure 12.
Results
The wave parameters for the three gauge positions at Ponce Inlet are given in
the selhts file:
αm (deg)
Date
I
J
Hmo(m)
Tp(sec)
96031202
15
21
5.25
12.8
-6.
96031202
15
65
4.13
12.8
-5.
96031202
28
49
2.86
12.8
18.
At the first gauge position (I = 15, J = 21), the wave height has shoaled slightly
(from 5.2 m at the boundary to 5.25 m) and turned slightly more shore normal
(from -7 deg at the boundary to -6 deg). At the second gauge (I = 15, J = 65),
located on the ebb shoal, the wave energy has dissipated because of breaking
(reduction of 21 percent in wave height from the offshore boundary). At the
most shoreward gauge (I = 28, J = 49), the energy has been dissipated
significantly (45 percent reduction in wave height from the offshore boundary)
and the mean direction has refracted from -7 deg at the boundary to 18 deg in the
outer throat. The wave directions at this gauge are turning to align normal to the
ebb shoal that is located to the south of the gauge (positive angles are more
southerly directed and negative angles are more northerly directed).
The trends of wave-height reduction and turning of the wave angle can also
be illustrated by examining the one-dimensional wave spectra plotted in
Figure 13. The shape of the spectra stays quite similar, but the energy is reduced
because of depth-limited breaking from the offshore to the outer throat gauge.
Another way to view the spectrum is to integrate over all frequencies to examine
the directional distribution of the wave energy (Figure 14). The directional
distribution narrows as well as reduces in energy between the offshore and ebb
shoal gauges because of refraction. Between the offshore/ebb shoal gauges and
51
Chapter 6 Example Applications
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