Relevance of acoustic methods to quantify bedload transport and bedform dynamics in a large sandy-gravel-bed river

Abstract

Abstract. Despite the inherent difficulties in quantifying its value, bedload transport is essential for understanding fluvial systems. In this study, we assessed different indirect bedload measurement techniques with a reference direct bedload measurement in a reach of a large sandy-gravel-bed river. An acoustic Doppler current profiler (aDcp), the dune tracking method (DTM) and hydrophone measurement techniques were used to determine bedload transport rates by using calibration with the reference method or by using empirical formulas. This study is the first work which attempted to use a hydrophone to quantify bedload rates in a large sandy-gravel-bed river. Results show that the hydrophone is the most efficient and accurate method for determining bedload fluxes in the Loire River. Although further work is needed to identify the parameters controlling self-generated sediment noise, the calibration procedure adopted in this study allows a satisfactory estimation of bedload transport rates. Moreover, aDcp and hydrophone measurement techniques are accurate enough to quantify bedload variations associated with dune migration.

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

“…Indirect monitoring techniques provide large spatial coverage of river transects at high temporal resolution, reduce personal risk related to in-stream sampling, and enable consistent data collection at widely varying flow conditions including floods (e.g. Gray et al, 2010;Rickenmann, 2017;Geay et al, 2020;Bakker et al, 2020;Choi et al, 2020;Le Guern et al, 2021). The drawback of these monitoring technologies is that in order to provide quantitative measurements, they require intensive calibration through direct bedload sampling with retention basins (Rickenmann and McArdell, 2008), slot samplers (e.g.…”

Migrating bars influence the formation and dynamics of their peers in large sandy‐gravel bed rivers

“…The 90th percentile of the sediment grain size distribution ( D 90 ) is approximately 3.3 mm, varying from 0.5 to 15.7 mm (Le Guern, 2021). Bedload transport occurs for a wide range of flow discharges (Le Guern et al, 2021), even during low flow periods, when bars emerge ( Q < 500 m 3 s −1 ). Since 1899, migrating bars have been observed in this area (Mille & Robert, 1899).…”

Bedload transport: beyond intractability

“…Although in other rivers, depending on how and when sediment is entrained and transported and the state of the bed surface, different hysteresis patterns have also been observed [ 47 , 48 ]. Measurements from the Loire River, France, and the Environmental Research Centre (University of Tsukuba, Japan) flume exhibit variations in the transport rate that are linked to the movement and architecture of bedforms [ 49 , 50 ]; and in the step-pool Torless Stream, New Zealand, transport rates during and between storms depend on the amount of sediment, derived from gullies and bank collapse, that is held in storage in the channel [ 51 ]. Regardless of source, in all cases, sediment availability varies across the entire range of ω ∗ .…”