Current field. No current field file is specified for this case.
Results
The results of greatest interest for this case are the wave parameters at the
proposed borrow site (I = 85, J = 25). The wave height is 1.52 m, the peak
period is 4.6 sec, and the direction is 0 deg (from the west, for this grid
orientation). The output file with selected wave parameters is given as follows
(header has been added):
αm(deg)
Date
I
J
Hmo(m)
Tp(sec)
980923 25
25
0.86
3.2
0.
980923 50
25
1.22
3.9
0.
980923 75
25
1.45
4.4
0.
980923 85
25
1.52
4.6
0.
980923 95
25
1.55
4.7
0.
980923 96
25
1.53
4.7
0.
980923 97
25
1.50
4.7
0.
980923 98
25
1.47
4.8
0.
980923 99
25
1.23
4.8
0.
980923 100
25
0.59
4.8
0.
These output wave parameters across the long axis of the bay demonstrate
the wave growth as a function of distance along the fetch. These wave heights
and periods are plotted as a function of distance in Figure 17. The wave height
grows with fetch until the depth decreases on the eastern shore of the bay, and the
wave height decays because of depth-limited breaking. The wave direction down
the long axis of the bay is aligned with the wind direction (0 deg). Figure 18
shows selected one-dimensional spectra along the long axes of the bay (legend
provides I, J locations). Moving from west to east (I = 25 to 95), the peak
frequencies decrease (peak periods increase) and the total energy increases, as the
waves grow from input wind energy. Between I = 95 and 100, the energy density
decreases because of depth-limited breaking. These one-dimensional spectra
were calculated from the spec.out file by integrating the spectra over all
directions.
To evaluate the impacts of the borrow site on the shoreline or the sediment
infilling rate at the borrow site, additional STWAVE runs would be required.
Typically, the local wave climate would be examined, and representative as well
as maximum wind conditions would be used as input for multiple model runs.
Results from these runs would then be used statistically to evaluate sediment-
transport potential at the borrow site and along the shoreline. Note that the
strongest wind speed does not necessarily lead to the largest waves or largest
sediment-transport rates. Wind direction is also a critical parameter.
This example of wave growth was for a completely enclosed basin. The
wave growth capabilities of the model are also applicable on the open coast. For
open-coast applications, the input spectrum would likely not equal zero, and the
offshore and lateral grid boundaries would not be land. For open coastal
57
Chapter 6 Example Applications
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