ERDC/CHL CHETN-I-67
June 2003
with 95 percent confidence. The average wave height along T2 will be in the range of 0.28 0.01 m
with 95 percent confidence.
The two transects provide a general overview of wave height within the harbor. However, because of
the significant variability in wave height along each one as a function of position and water depth, it
is difficult to compare wave energy between the two configurations based on an average wave height
along these transects. Another approach was to average the wave heights within limited areas or
boxes adjacent to the PP and CD. Each box contains many nodes from the CGWAVE model, each
with a predicted wave height value. Figure 4 shows a set of seven boxes (i.e., boxes 1 to 7) in the
vicinity of the PP and four boxes (i.e., boxes 8 to 11) adjacent to the CD. Boxes 1 and 2 are adjacent
to the westerly pier, boxes 4 to 6 the easterly pier, box 3 in between the two piers, and box 7 contains
the offshore docking area. Boxes 8 and 9 are in the vicinity of the boat ramp of the CD and boxes 10
and 11 are to the east. The end points of T1 and T2 can be seen in the interior of boxes 3 and 11,
respectively.
Figure 13 shows the average wave heights in each box H for the three wave periods. The PP boxes
(1 to 7) are to the left of the vertical red line and the CD boxes (8 to 11) are to the right. For the PP
boxes, the highest wave heights occur for waves traveling to the west (180 deg). For the CD boxes,
the highest heights occur for waves traveling predominantly to the southwest (225 deg).
The maximum wave heights HMax and their box locations from Figure 13 are shown in Table 2 for
the boxes in the PP and CD areas. Averaged over all boxes in the PP area, the maximum average
wave heights HAll = 0.23, 0.26, and 0.23 m for T = 6, 10, and 16 sec, respectively. All maximum
values are for waves traveling to the west. Averaged over all boxes in the CD area, the maximum
average wave heights HAll = 0.26, 0.25, and 0.23 m for T = 6, 10, and 16 sec, respectively. All
maximum values are for waves traveling to the southwest for the CD boxes. Finally, the 95 percent
confidence intervals for average wave height inside all boxes for all wave conditions are 0.16 0.02
m in the PP boxes and 0.16 0.03 m in the CD boxes. In general, the box area wave heights
correlate well with the predicted values for the two transects. The average wave heights for the
boxes are smaller than the transect averages since they only cover the shallower areas that have
experienced greater energy dissipation (e.g., further wave diffraction behind the breakwater, energy
losses due to bottom friction and wave breaking, etc.).
AUTHORIZED BREAKWATER WAVE HEIGHTS: The authorized breakwater gap was 91 m
(300 ft), or 30 m (100 ft) shorter than the existing breakwater gap. The analysis in this section is
similar to the previous section for the existing configuration. Figure 14 is a contour plot of the H for
the T = 6 sec waves and three wave directions, similar to Figure 10. The wave patterns for all wave
periods are similar to the existing breakwater, except that the smaller gap reduces the extent of the
wave incursion into the harbor.
Figures 15 and 16 show the predicted wave heights H along T1 and T2, respectively, for the three
wave periods T = 6, 10, and 16 sec for the authorized configuration. For transect T1 and waves
going to the CD, the narrower gap significantly reduces wave energy inside the harbor for waves
traveling to the southwest (green short dash line). This is in agreement with OCTI (2001) findings.
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