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.
Highlights
Worldwide, rivers are in crisis (Vörösmarty et al, 2010)
The acoustic Doppler current profiler (aDcp) dataset is composed of 96 simultaneous measurements of apparent bedload velocity and bedload transport meter Arnheim (BTMA) samplings (Fig. 3 and Appendix B)
A reduced major axis (RMA) regression has been computed between these two variables with a coefficient of determination (COD) R2 equal to 0.51: qs = 1456Va − 2.44
Summary
While changes in flow characteristics and fragmentation are well known (Grill et al, 2019), the impacts of human activities on the sediment budgets are as yet underrepresented (Kondolf et al, 2018). It is a prerequisite to an accurate estimation of global sediment budgets delivered by rivers to oceans (Syvitski and Milliman, 2007), to better understand bedform dynamics in river channels (Best, 1988; Bertoldi et al, 2009; Rodrigues et al, 2015; Claude et al, 2014) and to reproduce satisfactorily morphodynamic processes with numerical modelling (Mendoza et al, 2017; Cordier et al, 2020). In large rivers, this parameter remains difficult to estimate, mainly due to human and material resources required to collect accurate measurements. Since the 2000s, numerous studies have been carried out to process the signal captured by an acous-
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