Gp. Holdaway et al., Comparison between ADCP and transmissometer measurements of suspended sediment concentration, CONT SHELF, 19(3), 1999, pp. 421-441
For more than a decade, acoustic Doppler current profilers, ADCPs, have bee
n in common use measuring current profiles. It has been recognised over thi
s period that the backscattered ADCP signal could be used to not only evalu
ate the Doppler shift, but also offered the possibility to extract informat
ion on the scatterers. The present work reports on an analysis of opportuni
stic backscatter measurements collected using a 1 MHz ADCP system, to asses
s the potential of ADCPs to measure suspended sediment concentration quanti
tatively, The data were gathered during a water monitoring campaign which d
eployed ADCPs, near-bed and profiling transmissometers, and in situ bottle
samplers. Although the original study was not specifically designed to test
the capability of ADCPs to evaluate suspended sediment concentration, suff
icient data were collected to examine the use of ADCPs for such measurement
s. The backscattered amplitude from one ADCP beam was recorded for quality
control to assess the accuracy of velocity measurements. However, in this s
tudy these data have :also been used to examine the potential of ADCPs for
suspended sediment measurements. To investigate ADCPs in this role, the bac
kscattered signals from one range cell has been calibrated against in situ
bottle samples of the suspended material. Using this calibration, the backs
cattered signals have been inverted to give time series profiles of suspend
ed particulate matter. To assess these profiles, comparisons have been made
with in-situ calibrated profiling and moored transmissometers. The outcome
from the present study shows ADCP results which are comparable with the tr
ansmissometer observations, and clearly demonstrate the potential of ADCPs
for directly measuring suspended sediment profiles. (C) 1999 Elsevier Scien
ce Ltd. All rights reserved.