"Proceedings, Federal Interagency Workshop,
"Sediment Technology for the
21'st Century,"
St. Petersburg, FL, February 17-19,
1998"
Development of an Suspended Sediment Measurement System (SSMS)
By Robert Derrow II
Pre-Proposal
Issue/Problem
Use of acoustic techniques to measure suspended sediment concentration have
been ongoing for several years (Urick, 1948). In most of these systems a
short burst of high frequency (>1 MHz) sound is emitted from a
transducer(s) and is scattered off the sediment in suspension. The
magnitude of the backscattered energy is related to the concentration and
size of the sediment. Current technology can measure suspended sediment
concentration with limited size distributions with high accuracy (Schat,
1997), but success has been limited at determining sediment size
distribution to a reasonable accuracy. Very high concentrations where
multiple scattering effects are more dominant are especially problematic
(Crawford and Hay, 1993; Thorne et al., 1994). We propose to develop a
system to minimize the current limitations mentioned above.
Beneficiaries
This instrument would be useful to all organizations that are involved
with, or concerned about, knowing what the size and concentration of
sediment transported in suspension whether in a stream, river, estuary, or
marine environment.
Objectives
To develop a lab/field useable system that will remotely monitor suspended
sediment concentration and size distribution in various measurement
areas.
Approach
A system will be built from custom and COTS components that utilize 3 or
more acoustic transducers that operate at different frequencies. The
backscatter from the individual transducers will be analyzed individually and
in pairs to build up sediment size/backscatter ratio curves that produce
average concentration/size information about the sediment profiles. To
start with, the system will be calibrated using the existing Suspended
Sediment Calibration Tower. Then laboratory flume measurements will be
conducted followed by field tests at an instrumented flume in the Goodwin
Creek Watershed.
Funding
|
Funding by Fiscal Year: |
|
|
| FY98 | $100K |
| FY99 | $100K |
| FY00 | $100K |
Principal Investigator
Rob Derrow & Roger Kuhnle
References
Crawford, A.M. and Hay, A.E., 1993, Determining suspended sand size and
concentration from multifrequency acoustic backscatter, J. Acoust. Soc.
Am., 94 (6), 3312-3324.
Schat, J., 1997, Multifrequency acoustic measurement of concentration and
grain size of suspended sand in water, J. Acoust. Soc. Am., 101 (1),
209-217.
Thorne, P.D., Hardcastle, P.J., Flatt, D, and Humphery, J.D., 1994, On the
Use of Acoustics for Measuring Shallow Water Suspended Sediment Processes,
IEEE J. Oceanic Engineering, 19 (1), 48-57.
Urick, R.J. 1948, The absorption of sound in suspensions of irregular
particles, J. Acoust. Soc. Am., 20, 283-289.
Workshop Contributions
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