Acoustic sampling effects on bedload quantification using acoustic Doppler current profilers

Abstract

ABSTRACT This paper provides an evaluation of a hydro-acoustic technique for efficient quantification of the bedload transport in riverine environments. Stationary bedload measurements were conducted simultaneously at different study sites, using three different acoustic Doppler current profilers (ADCP) working at four different frequencies. The raw apparent bedload velocities were de-spiked and filtered in a streamwise direction. Then, functional correlations were observed between the magnitudes of the apparent velocities and the bedload transport rates measured by the conventional bedload sampler. Each ADCP yielded different results because of the different frequency backscatter sensitivity and acoustic penetration in the active bedload layer. In addition to the frequency, other acoustic parameters such as the percentage of the filtered data, transducers width, beam opening angle, beam-grazing angle and the pulse length, contributed to the acoustic bedload sampling. The influence of these parameters is examined, and recommendations are given for the performance and limitations of each instrument.