Environmental Engineering Reference
In-Depth Information
understanding properties of sediment transport in
rivers. Some characteristics common to these fi ve
technologies include the following:
•
all address measurement of fl uvial-sediment char-
acteristics that are diffi cult, expensive, and (or) dan-
gerous to directly measure with suffi cient frequency
to adequately defi ne their spatial and temporal
variability;
•
all are generally affordable - ranging from about
the cost of a fully equipped turbidimeter (about
US$5000 in 2008) to about sixfold that cost for the
more expensive laser-diffraction technologies;
•
all (with the possible exception of the laser-
diffraction and digital-optic technologies) require
site-specifi c calibrations, although the need for
calibration is expected to diminish over time;
•
all require derivation of coeffi cients equating
values recorded by the surrogate instrument to the
mean cross-section constituent value;
•
all but turbidity, which is endorsed by the USGS
for use in operational sediment-monitoring pro-
grams, require additional testing and evaluation.
The USGS endorsement of SSC and SSL computa-
tions from turbidity measurements notwithstanding,
none of the technologies is suitable for monitoring
all the suspended-sediment characteristics in all
rivers under all fl ow and sediment-transport condi-
tions. Nevertheless, if care is exercised in matching
surrogate technologies to appropriate river and sedi-
ment conditions, it is becoming possible to monitor
SSC and SSL remotely and continuously in a variety
of rivers over a range of fl ow and sedimentary condi-
tions within generally acceptable accuracy limits.
Endorsement and broad-scale deployment of certifi -
ably reliable sediment-surrogate technologies sup-
ported by operational and analytical protocols are
revolutionary concepts in fl uvial sedimentology. The
benefi ts could be enormous, providing for safer,
more frequent and consistent, arguably more accu-
rate, and ultimately less expensive fl uvial-sediment
data collection for use in managing the world's sedi-
mentary resources.
USGS, Minneapolis, Minnesota, and Vicksburg,
Mississippi, respectively. Annette L. Ledford, USGS,
Reston, Virginia, devoted considerable effort in the
development of the chapter's fi gures and tables.
Arthur J. Horowitz's (Atlanta, Georgia, USA)
research on the sedimentary properties of selected US
rivers was excerpted. The laser-optic and hydroa-
coustic sections benefi ted from research led by David
A. Topping, USGS, Flagstaff, Arizona.
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Acknowledgments
This chapter benefi ted from the contributions and
efforts of several individuals other than the authors.
The manuscript was improved by the reviews pro-
vided by Michael Singer, University of St Andrews,
UK, and James D. Fallon and Broderick E. Davis,
