ERDC/CHL CHETN-I-65
June 2002
The transformed NDBC buoy significant heights, peak periods, and directions generally compare
very well with Gauge CA002 data and were accepted as a reasonable auxiliary source of
nearshore incident waves for Morro Bay Harbor.
The high-resolution array at the Harvest Platform collected directional data between November
1991 and January 1999, with several lengthy gaps in 1996 and 1997. The array was accidentally
hit by a vessel on 28 March 1998, and reliable directional data are not available after that date. A
rose of plot of significant wave heights during the years 1993-1995 shows wave climate
characteristics (Figure 3). As with the NDBC buoy, wave climate is dominated by waves from
northwesterly directions, with a small secondary component of wave climate rotated slightly
more toward the west. Overall, wave climate is remarkably similar at the two deepwater gauge
locations. The directional buoy at Harvest Platform began operation in November 1995, and it is
still operational. After a large gap from March 1996 until March 1998, the buoy has provided a
consistent, reliable record of directional waves to augment and extend the array data. Waves
from the Harvest Platform gauges were transformed, using the transformation approach as used
for the NDBC buoy data, to be comparable to wave data from the Morro Bay directional Gauge
CA002. An example comparison between the Harvest Platform data and Gauge CA002 data is
shown in Figure 5. Transformed significant wave heights, peak periods, and directions generally
compare very well. The data also compares well with transformed NDBC buoy data. As with the
NDBC buoy data, the transformed Harvest Platform data were accepted as a reasonable auxiliary
source of nearshore incident waves for Morro Bay Harbor.
With directional wave data from the NDBC buoy and Harvest Platform transformed to be
representative of nearshore incident waves at Morro Bay Harbor, a continuous incident wave
record can be reconstructed over the full time period since the harbor entrance was modified. A
time-history of nearshore significant wave height from available sources is summarized in
Figure 6.
The inner harbor gauge deployed under the monitoring program operated successfully during
most of the time frame. It provided significant height and peak period wave parameters. The
gauge was well-protected from incident ocean waves and significant heights were generally low.
The second location for the gauge in the latter stages of the monitoring was more exposed than
the initial location, but significant wave heights were still relatively low. Energetic events at
Gauge CA001 appeared to be more related to local winds than to incident ocean wave
conditions. Peak periods were usually representative of either incident ocean waves or much
longer period oscillations affecting the semienclosed harbor area with comparable or greater
energy than the residual ocean waves.
COMPARISON OF PROTOTYPE AND PHYSICAL MODEL WAVE ESTIMATES: The
modified entrance channel design for Morro Bay Harbor was based primarily on physical model
experiments; however, numerical model experiments played a role in early phases of project
development. Both physical and numerical model studies included the transformation of incident
waves over local entrance bathymetry, through the breakwater gap, and into the protected harbor
area. One monitoring study objective was to use prototype data to evaluate the accuracy and
effectiveness of the model studies. Comparison to physical model studies is considered in this
section and numerical models studies is considered in the next section.
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