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DIVANI CARAVEL HOTEL - ATHENS, GREECE
SEPTEMBER 7-9, 2022
Innovative water management in a changing climate
IAHR 2022 | Abstract Book
A new hyperband acoustic profiler – Suspended particulate matter monitoring
in the river in France, example on the Rhône and Isère river
Stéphane FISCHER1, Gilles PIERREFEU2, Marie BURCKBUCHLER1, Thierry FRETAUD2
1UBERTONE, France
email: info@ubertone.fr
2 Compagnie Nationale du Rhône, France
email: g.pierrefeu@cnr.tm.fr
ABSTRACT
Suspended Particulate Matter (SPM) measurements are a very important challenge of operational flow
monitoring. The ANR project MESURE led to the development of a compact dual-frequency ABS prototype
tested on a river. Following this research project, a compact commercial version was developed by Ubertone,
composed of a hyperband acoustic module, and of a battery-wifi-logger module. In this paper, we present the
deployment of this UB-SediFlow during sediment managing operations. The UB-Sediflow was installed on a
floating board. In parallel, another team collected SPM reference samples to qualify UB-SediFlow. Post-
processing analysis over a large frequency range gave quality data and this campaign showed an easy
deployable instrument allowing real time data visualization.
1. Introduction
The ANR project MESURE (ANR-16-ASMA-0005, 2017-2020) proposed to advance further regarding the
SPM metrology (sediment concentration, size and flux) using multifrequency hydro-acoustic observations. A
dual-frequency ABS (Acoustic Backscattering System) prototype was first developed by Ubertone and tested
in laboratory and field campaigns. This prototype was then upgraded to allow a larger range of emission
frequencies. In this paper, we present field campaign results of the hyperband ABS UB-SediFlow.
2. Method
2.1. Hyperband ABS
The UB-SediFlow is a multi-frequency acoustic profiler (Fig. 1), which measures backscattered echo profiles
along 4 acoustic beams. The system is composed of two hardware modules linked by a cable. The waterproof
acoustic module (up to 20m) includes 4 wideband transducers (covering the full range 300kHz to 6MHz) and
an acoustics electronic board. The splashproof logger (acquisition and communication module) includes a
battery (autonomy of 12 hours) and communicates through wifi (signal range between 50 and 100m).
Fig. 1. From left to right : the UB-SediFlow on a floating board, the acoustic module and the user interface
The acoustic module UB-Sediflow was installed on a CNR floating board (Fig. 1) which was deployed with a
rope from the bridge on the river at a fixed position or moving to get a transect.
2.2. Theory
The acoustic backscattered intensities measured by acoustic profilers can be inverted through different
methods to get concentration and grain size information (Hurther, 2011). All the methods derive from the sonar
equation (Thorne, 1997), which includes the necessity of a calibration.
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DIVANI CARAVEL HOTEL - ATHENS, GREECE
SEPTEMBER 7-9, 2022
Innovative water management in a changing climate
IAHR 2022 | Abstract Book
2.3. Field measurements
During the sediment managing operations APAVER of May 2021 on the Rhône river, France, the UB-
SediFlow was set with 6 acoustic configurations: 0.5 ; 1.0 ; 1.5 ; 2.3 ; 4.5 and 5.2 MHz. The inversion of the
acoustic data has been compared with pycnometer samples and the CNR’s reference measurement over 5 days
(May 19 to 21, 25 and 26th, 2021).
3. Results and discussion
When analysing the acoustic data, the distinction between fine and coarse particles (<100μm<) is made. The
fine sediment concentration estimator was calibrated on May 19th in the morning with a pycnometer near the
water surface at the very beginning of the campaign. The coarse sediment concentration estimator is calibrated
near the water surface on the 20th, during a peak of concentration.
The acoustic measurement of the concentration of fine sediments has an uncertainty close to the 20% of the
reference pycnometer. Figure 2 shows concentration evolutions on May 20th according to different
measurement methods, including the reference value computed by the CNR from several methods.
Fig. 2. Concentrati on measureme nts, in the first meter under the surface, by UB-SediFlow (dots) and pycnometer (squares) compared to
reference value (line), on May 20th.
Fig. 3. Coarse particles concentration profiles (in g/L) measured by acoustic method, on May 19th in the afternoon.
Coarse particle (>100microns) concentration measurements over the whole vertical allow a quantification of
the concentration along the depth (see Fig. 3 on May 19th afternoon). This measurement could be improved
with two points of calibration at the surface and near the bottom.
4. Conclusion
The UB-SediFlow gave quality data over a large frequency range and showed an easy deployable instrument
allowing real time data visualization. The first result led the CNR team to improve the knowledge of sand
flux spatially and temporally. The advantage of this sensor is the optimization of the number of samples on
site to estimate SPM flux. A laboratory calibration campaign on the DEXMES facility is planned to confirm
consistency of the field in-situ calibration. The next step will be to qualify this instrument with more SPM
reference values.
References
Thorne PD & Hardcastle PJ (1997) Acoustic measurements of suspended sediments in turbulent currents and comparison with in-situ
samples, Journal of the Acoustical Society of America, vol. 101, p. 2603–2614.
Hurther, D., Thorne, P. D., Bricault, M., Lemmin, U. & Barnoud, J.-M. (2011). A multifrequency Acoustic Concentration and Velocity
Profiler (ACVP) for boundary layer measurements of fine-scale flow and sediment transport processes, Coastal Engineering, vol. 58,
p. 594–605
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