Field and flume measurements with the impact plate: Effect of bedload grain‐size distribution on signal response

Nicollier, Tobias; Rickenmann, Dieter; Hartlieb, Arnd

doi:10.1002/esp.5117

Cited by 23 publications

(49 citation statements)

References 45 publications

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“…While these particles were being transported over the SPG system, the full raw geophone signal was recorded. Up to 33 repetitions were conducted until a representative range of amplitude and frequency values for each grain-size class were obtained (Nicollier et al, 2021a). The same procedure was repeated for two different flow velocities ( = 1.6 m s -1 and 2.4 m s -1 ).…”

Section: Controlled Flume Experimentsmentioning

confidence: 99%

“…Habersack et al, 2017;Halfi et al, 2020) or mobile bag samplers (e.g. Bunte et al, 2004;Dell'Agnese et al, 2014;Hilldale et al, 2015;Mao et al, 2016;Kreisler et al, 2017;Nicollier et al, 2021a).…”

Section: Introductionmentioning

confidence: 99%

“…For example, the experiments of Wyss et al (2016b) showed that higher flow velocities induce a weaker SPG signal response per unit of transported sediment. More recent controlled experiments have highlighted another important site-dependent factor influencing the SPG signal response, namely the grain-size distribution (GSD) of the transported bedload (Nicollier et al, 2021a), where coarser grain mixtures were shown to yield a stronger signal response per unit bedload weight.…”

Section: Introductionmentioning

confidence: 99%

“…Discussion started: 9 February 2022 c Author(s) 2022. CC BY 4.0 License.of packet amplitude and frequency from the single-grain-size experiments conducted at the flume facility using the Albula setup(Nicollier et al, 2021a). For each class , the lower threshold is based on the maximum amplitude of the packet's envelope [V] and the upper threshold is based on the ratio / [V Hz-1 ].…”

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confidence: 99%

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Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Nicollier

Antoniazza

Ammann

et al. 2022

Preprint

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Abstract. Substantial uncertainties in bedload transport predictions in steep streams have triggered intensive efforts to develop surrogate monitoring technologies. One such system, the Swiss plate geophone (SPG), has been deployed and calibrated in numerous steep water courses, mainly in the Alps. Calibration relationships linking the signal recorded by the SPG system to the transported bedload can vary substantially between different monitoring stations, likely due to site-specific factors such as the flow velocity and the bed roughness. Furthermore, recent controlled experiments have shown that site-specific calibration relationships can be biased by elastic waves resulting from impacts occurring outside the plate boundaries. Motivated by these findings, here we present a hybrid calibration procedure derived from flume experiments and an extensive dataset of 308 calibration measurements from four different field monitoring stations. Our main goal is to investigate the feasibility of a general, site-independent calibration procedure for inferring fractional bedload transport from the SPG signal. First, we use flume experiments to show that sediment size classes can be distinguished more accurately using a combination of vibrational frequency and amplitude information than by using amplitude information alone. Second, we apply this amplitude-frequency method to field measurements to derive general calibration coefficients for ten different grain-size fractions. The amplitude-frequency method results in more homogeneous signal responses across all sites and significantly improves the accuracy of fractional sediment flux and grain-size estimates. We attribute the remaining site-to-site discrepancies to large differences in flow velocity, and discuss further factors that may influence the accuracy of these bedload estimates.

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Section: Controlled Flume Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Nicollier

Antoniazza

Ammann

et al. 2022

Preprint

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“…Full-scale controlled flume experiments were performed with natural bedload particles varying in size (Nicollier et al, 2019(Nicollier et al, , 2020(Nicollier et al, , 2021a, using an outdoor experimental facility at the Oskar von Miller Institute of the Technical University of Munich in Obernach, Germany. The entire experimental system can be divided into serval parts including the flume channel made of concrete, the measuring reach equipped with different types of sensors (Fig.…”

Section: Experimental Set-upmentioning

confidence: 99%

Signal response of the Swiss plate geophone monitoring system impacted by bedload particles with different transport modes

Chen

Nicollier

et al. 2021

Preprint

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Abstract. Controlled experiments were performed to investigate the acoustic signal response of the Swiss plate geophone (SPG) system impacted by bedload particles varying in size, impact angle and transport mode. The impacts of bedload particles moving by saltation, rolling, and sliding were determined by analyzing the experimental videos and corresponding vibration signals. For a particle impact on the bed or on the geophone plates, the signature of the generated signal in terms of maximum amplitude, number of impulses and centroid frequency was extracted from the raw monitoring data. So-called signal packets were determined by performing a Hilbert transform of the raw signal. The number of packets was calculated for each transport mode and for each particle size class, with sizes ranging from 28.1 mm to 171.5 mm. The results show how the number of signal impulses per particle mass, the amplitude of the signal envelope, and the centroid frequency change with increasing particle size, and they also demonstrate the effect of bedload transport mode on the signal response of the SPG system. We found that there is a general increase in the strength of the signal response or in the centroid frequency when the transport mode changes from sliding to rolling to saltation. The findings of this study help to better understand the signal response of the SPG system for different bedload transport modes, and may also contribute to an improvement of the procedure to determine bedload particle size from the SPG signal.

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Strengths and weaknesses of acoustic pipe microphone systems in ephemeral, sandy, gravel‐bed rivers

Stark,

Cadol,

Varyu

et al. 2024

Earth Surf Processes Landf

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We calibrated an acoustic pipe microphone system to monitor bedload flux in a sandy, gravel‐bed ephemeral channel. Ours is a first attempt to test the limit of an acoustic surrogate bedload system in a channel with a high content of sand. Calibrations varied in quality; significant data subsetting was required to achieve R2 values >0.75. Several data quality issues had to be addressed: (1) apparent pulses, which occur when a sensor records an impulse from sediment impacting the surrounding substrate rather than directly impacting the sensor, were frequent, especially at higher signal amplifications. (2) The impact sensors were frequently covered by gravel sheets. This prompted the development of a cover detection protocol that rejected part of the impact sensor record when at least one sensor was partially or fully covered. (3) Because of the lack of sensor sensitivity to impacts of sand‐sized particles, which was anticipated, and the considerable sand component of bedload in this channel, a grain size‐limited bedload flux was estimated. This was accomplished by sampling the bedload captured by slot samplers and evaluating the variation of grain size with increasing flow strength. This considerably improved the results when compared to attempts at estimating the flux of the entire distribution of grain sizes. This calibration is a successful first attempt, though the impact sensors required several site‐specific calibration steps. A universal set of equations using impact sensors to estimate bedload transport of fine‐gravel with a large content of sand remains elusive. Notwithstanding, our study demonstrates the utility of impact sensor data, producing relatively low root mean square errors that are independent of measurements of flow strength (i.e. discharge). These tools will be particularly useful in settings that would benefit from new methodologies for estimating bedload transport in sand‐rich gravel‐bed rivers, such as the American desert Southwest.

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Field and flume measurements with the impact plate: Effect of bedload grain‐size distribution on signal response

Cited by 23 publications

References 45 publications

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Signal response of the Swiss plate geophone monitoring system impacted by bedload particles with different transport modes

Strengths and weaknesses of acoustic pipe microphone systems in ephemeral, sandy, gravel‐bed rivers

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