ERDC/CHL CHETN-I-65
June 2002
(for CA002) continued until the gauge failed during a major storm on 28 October 1999.
Nondirectional data recording resumed after a service visit on 6 April 2000. The nondirectional
gauge inside the harbor entrance, CA001, was a single bottom-mounted pressure gauge. Wave
data were recorded internally on the same schedule as Gauge CA002. Initial deployment was
along the western edge of the navigation channel (Site 1, Figure 2). Data from initial deployment
are available from 11 September 1998 to 8 February 1999. The gauge was reactivated on
24 March 1999 and continued collecting data until 25 Jan 2000. The gauge was moved to Site 2
and reactivated on 6 April 2000 and continued collecting data until the end of the gauging
program. The nondirectional buoy was a Waverider accelerometer buoy at the landward edge of
the deepened, exposed entrance. The buoy gauge was chosen because a bottom-mounted gauge
at this location would be overly vulnerable to vessel traffic and bottom sediment movement. The
buoy transmitted data in real-time to a receiver placed in a nearby office. Buoy data were
processed by a contractor to give wave parameters every 20 min. The gauge failed on
22 November 1998, during the same storm that affected Gauge CA002. The gauge was
reactivated and operated during the brief period 1-20 May 1999. It was again reactivated on
19 July 1999 and continued collecting data until an intense storm on 31 Jan 2000.
Since outages of Gauge CA002 and the absence of directional data during much of the
monitoring period limited its usefulness for defining incident wave conditions at the project site,
other possible sources of incident wave data were pursued. Two consistently maintained offshore
directional wave gauge sites are available within a reasonable distance from Morro Bay
(Figure 3). North of the project site, the National Oceanic and Atmospheric Administration
(NOAA) National Data Buoy Center (NDBC) operates a directional wave buoy near Monterey,
CA. South of the project site, the Scripps Institution of Oceanography (SIO) collects directional
data at the Harvest Platform, a Texaco Oil Company oil-production facility. Two directional
wave gauges operated at Harvest Platform within the monitoring program time period: a spatial
array of pressure gauges and an accelerometer buoy. Both the Monterey buoy and Harvest
Platform gauges provide directional wave data seaward of localized nearshore transformation
effects. With the wind and wave climate characteristic to the California coast, especially the
large spatial extent of major storms, it was reasonable to consider these gauges as possible
sources of incident offshore waves at Morro Bay.
The NDBC directional wave buoy has been collecting directional data since 1991, with
occasional short gaps. A rose plot of significant wave heights during the years 1995-2000 depicts
wave climate characteristics (Figure 3). Waves generally approach from directions between west
and north-northwest. A secondary component of wave climate is evident from the south-
southwest, but this component is overshadowed by the more commonly-occurring and typically
more energetic waves from northwest. Waves recorded at the NDBC buoy may be reasonably
representative of deepwater offshore wave conditions at Morro Bay; however, they must be
transformed into shallow nearshore waters representative of the entrance to Morro Bay before
they can be considered comparable to data from the Morro Bay directional Gauge CA002.
Bottom contours seaward of Gauge CA002 are sufficiently shallow to affect approaching waves
and are reasonably straight and parallel. A standard wave transformation program based on a
directionally-spread wave condition propagating over straight, parallel bottom contours was
applied to the NDBC buoy data obtained during 1995-2000. Results were compared to
Gauge CA002 during the times it was operational. An example comparison is shown in Figure 4.
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