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St. Petersburg Field Center Hosts Workshop on Ordnance Mine Burial
By Peter Howd
March 2001 |
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The Office of Naval Research (ONR), Marine Geology and Geophysics Program held its "Coastal
Processes Driving Mine Burial" workshop at the St. Petersburg Field Center (SPFC) on January
30th-February 1st. Peter Howd of the University of South Florida St. Petersburg campus was the
local contact. Objectives of this ONR 6.2 program are to use both field and laboratory
measurements in conjunction with numerical models to increase prediction of the fate of
mines placed on the seabed in shallow marine environments. Approximately 40 researchers from
six countries representing academia, the private sector and government agencies attended the
workshop. The SPFC (Terry Kelley) receives funding from ONR to help support field operations
associated with this program.
The objectives of the workshop were to begin establishing experimental designs for the program
through discussion as a collected group of modelers, and laboratory and field investigators.
During the workshop, two field sites were selected for extensive measurement programs in the
coming years. The sites are the west Florida inner continental shelf (WFS), and the new WHOI
coastal observatory based on Martha's Vineyard. The selection of the WFS site was helped in
part by the extensive background information resulting from the 1990s USGS study headed by
Guy Gelfenbaum, now at the Menlo Park office.
For the coming year, USF College of Marine Science investigators have been funded by ONR to:
Conduct detailed geoacoustic and sedimentological surveys of the Indian Rocks Beach inner shelf
(IRB) area to obtain baseline geological information, such as, high-resolution bathymetry,
sediment thickness, surficial variability in sediment acoustic patterns and textures, and the
shallow subsurface (1-2 m) sedimentary facies patterns. A boomer seismic system or a CHIRP
profiler will be used for mapping sediment thickness. A 100-kHz EG&G Model 272 TD side-scan
sonar system will be deployed concurrently with a subbottom profiler to acquire backscatter
data using a 300-m-swath coverage. This backscatter coverage is appropriate for detecting major
surficial-sediment facies changes and the presence of bedforms as small as 0.5 m in wavelength.
In addition, 300-kHz multibeam bathymetry and backscatter data will be collected in reconnaissance
mode using a Kongsberg Simrad EM3000 (300 kHz) multibeam sonar system. Seabed textural changes
will be assessed using backscatter data sets from the side-scan and multibeam systems and
vertical-beam bottom classification techniques using QTC-IMPACT software designed to classify
seafloor sedimentary facies based on bottom-sampling calibrations.
Integrate these geophysical techniques into the quantitative process studies. We will conduct
an assessment of the calibration and repeatability of the various acoustic systems as we
transition from qualitative to quantitative applications of these geophysical tools. A key
component of the study will include ground-truthing of the geophysical data sets with sedimentary
data. Sediment samples will be obtained using grab-sampling techniques and diver-deployed push
cores. Correlation analysis will be run between textural components, acoustic classification of
bottom types based on vertical beam wavelet analysis, and zonation of bottom types based on
side-scan sonar imagery.
Measure the hydrodynamic conditions that produce and maintain bedforms and shallow stratigraphy.
We will make detailed measurements of the combined-flow bottom boundary layer using a combination
of current meters. An upward-looking ADP will measure mean flows from approximately 80 cm above
the bed to near the surface. A tripod-mounted, downward-looking PC-ADP will measure the
instantaneous flows in roughly the bottom 75 cm (in 2.5-cm bins). A downward-looking ADV will
measure instantaneous flow at a point at rates of up to 25 Hz, allowing burst estimates of
turbulence and accurate calculation of higher moments (skewness and asymmetry) of the flow.
The downward-looking instruments will also function as altimeters. These spot measurements will
be put in context of local (~102 m2) changes using high-resolution rotary fan-beam and scanning
pencil beam sonars. Suspended sediment characteristics will be measured using acoustics and
optical sensors (OBS, LISST-100).
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March 2001
in this issue:
cover story:
Natural Hydrocarbons in Gulf of Alaska
Black History Month
Glacial Floods Video
Coastal Marsh Die-Back in Gulf of Mexico
Carbonate Beaches 2000
USGS Information: Electronic Age
CMG Program Webmasters
Leaky Coastal Margins / Karst Interest Group
Nat'l Sand & Gravel
Ordnance Mine Burial
Monterey Bay
Partnership Publications
Earthquake Hazards Video
March Publications List
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U. S. Department of the Interior | U.S. Geological Survey
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