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Instrument Calibrations and Water Column Profile Surveys of a Mixed-Sediment Mound
Grace M. Battisto, Virginia Institute of Marine Science (VIMS)
May 2001

Introduction


This work is being conducted in support of an ongoing investigation on sediment dispersal and evolution of a mixed-sediment disposal mound by the US Army Corps of Engineers. Repetitive water column surveys, suspended sediment concentration samples and bottom sediment grabs are being collected for calibration of Acoustic Doppler Current Profilers (ADCP) and Optical Backscatter Sensors (OBS) deployed by Carl Miller of the USACE Field Research Facility on the site of the disposal mound and immediate vicinity. The Virginia Institute of Marine Science, College of William and Mary, under the direction of Grace M. Battisto, will be performing the work.

• Scope of Work

•  Preliminary Bottom Grab and Suspended Sediment Results

Instrumentation


• Profiler - The profiler allows all the instruments (LISST, OBS, ADV, CTD, and compass) to be lowered through the water column at the same rate.

• LISST - Laser in-situ Scattering Transmissometer - The LISST is used to measure the grain size distribution of suspended sediment from 5 to 500 microns (silts, clays, and fine sands).

• CTD Gauge - The CTD measures the conductivity, temperature, and depth at the sensor height as the profiler is lowered through the water column. The conductivity and temperature are used to determine the salinity at each depth.

• OBS - Optical Backscatter Sensor - Backscattered light within the OBS sampling volume is used to estimate suspended sediment concentration at the sensor height.

• ADV - Acoustic Doppler Velocimeter - Sound emitted by an Acoustic transmitter is backscattered off of suspended particles within the sampling volume and detected by three receivers to estimate water velocity at a single location.

• ADCP - Acoustic Doppler Current Profiler - The ADCP measures the water velocities in 0.25 m (0.8 ft) bins from just below the instrument to the bottom of the water column, when mounted on a vessel.

• Smith-Mac Sediment Grab - Bottom sediments collected using the Smith-Mac allow coupling of sediment type and porosity (trapped water) with the water column properties measured with the ADCP and profiler.

• Click here to view images and read more about these instruments.

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