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Successful Deployment of Tripods and Moorings Off Southern California, Or "Ten Fingers, Ten Toes, and a Clear Deck at the End of the Day . . ."
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Tripods:
USGS tripods await deployment on the deck of the R/V R.G. Sproul.
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Working aboard the R/V R.G. Sproul between June 12th and June 15th, Coastal and Marine Geology
scientists from Menlo Park and Woods Hole successfully deployed an array of tripods and moorings
in San Pedro Bay off Huntington Beach in Southern California. Menlo personnel included Joanne
Thede Ferreira, Dave Gonzales, Marlene Noble, Kevin O'Toole, Hal Williams, and Jingping Xu. Woods
Hole personnel included Jonathan Borden, Rick Rendigs, and AndreŽ Ramsey.
Huntington Beach is a very popular swimming and surfing area that has been closed sporadically
during the past several summers because of bacterial contamination. Last month's deployment is
part of a comprehensive study designed by CMG scientists to determine pathways in the coastal
ocean that could carry contaminated material to Huntington Beach. The study is being conducted
in cooperation with the Naval Postgraduate School, Scripps Institute of Oceanography, Science
Applications International Corporation (SAIC), University of Southern California, and University
of California Irvine. One of many suspects for the contaminant source is a sewage outfall that
discharges treated effluent 5 mi seaward from Huntington Beach. The outfall is located in a very
complex section of the continental shelf, near the shelf break and adjacent to a prominent
submarine canyon.
Offshore Los Angeles:
Mooring locations shown on multibeam bathymetry of continental shelf and slope off Newport Beach
and Huntington Beach, Greater Los Angeles area. Yellow lines above the shelf break are 5-m contour intervals
from 10 m to 100 m water depth; blue lines below the shelf break are 20-m contour intervals from 120 m to
400 m water depth. Diagonal red line is sewage outfall pipe. Black lines shoreward of outfall pipe
represent lower course of Santa Ana River (on line with outfall pipe) and stormwater runoff
channels.
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The study partners will deploy an array of 13 moorings (see map) to investigate transport of water
and suspended materials through the region. The USGS moorings were the first to be deployed, and
they are the only moorings that include bottom tripods to determine how and when sediment re-suspension
occurs. An array of four tripods, the Naval Postgraduate School's anti-trawl-cage-mounted ADCPs
(Acoustic Doppler Current Profilers), four surface moorings and four sub-surface moorings occupy
the five USGS sites. Colleagues from cooperating institutions will deploy moorings at the remaining
sites in the next few weeks. The moorings will be out through mid-October (4 months).
The weather for last month's deployment was great, enabling us to set all the moorings on a single
day with daylight to spare! The second day, we picked up the Naval Postgraduate School's meteorological
buoy at Fish Harbor, deployed it, and spent the rest of the day taking grab samples across and along
the shelf. A cursory look at sediments collected suggests that those at the shelf break are coarser
than on the mid-shelf. The coarsest sediments seemed to be located along the shelf break adjacent
to the submarine canyon. This distribution is reminiscent of grain-size dispersal on the adjacent
Santa Monica Bay shelf (to the northwest). On the Santa Monica Bay shelf, energetic internal
tides and internal waves at the shelf break contribute to re-suspension and advection of fine
sediments. In October we may have the measurements to support similar sediment dynamics in San
Pedro Bay.
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July 2001
in this issue:
cover story:
Mapping Puget Sound
Biscayne Nat'l Park
Glacier Bay Cruise
Tripod Deployment
GIS Group Teaches Science
Juneteenth Celebration
Geochemical Processes
Geologic Discipline EMAC
Wetlands Meeting
Closing the Circle
Eric Thompson
NAGT Summer Interns
Woods Hole Interns
Jerry Parker Memorial
Gaye Farris Re-Elected to STC Exec Board
"Natural Gas Hydrates" Book
July Publications List
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U. S. Department of the Interior | U.S. Geological Survey
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