Bedload estimation in large sand-bed rivers using Acoustic Mapping Velocimetry (AMV)

Abstract

This paper describes the in-situ implementation of a recently developed bedload transport estimation method, called Acoustic Mapping Velocimetry (AMV). The method combines components and processing protocols from acoustic and image-based methods to provide velocity maps of bedforms migrating in the riverbed. The AMV implementation is illustrated with repeated Multibeam Echo Sounder (MBES) mappings that are acquired along longitudinal swaths over the entire transect of the study river sections. The paper exemplifies AMV implementation case studies leading to the estimation of bedload transport rates in two large sand-bed rivers: the Ohio and Mississippi rivers, in the USA. The analysis associated with these case studies emphasizes the importance of linking the characteristics of the bedform dynamics with the selection of the spatio-temporal parameters used during data acquisition for AMV processing (e.g., required length of the measurement section, and the effect of the time lag between the repeated surveys) for accurate quantification of bedform dynamics. The role of superimposed secondary small bedforms migrating over the large primary ones, in terms of their contribution to the sediment transport, is also discussed. The paper demonstrates the applicability of this novel technique, as a complement or stand-alone method for quantifying bedload transport in large sand-bed rivers, an area where the implementation of conventional methods is difficult and inadequate while the emerging measurement alternatives are not widely recognized yet.