Imaging of Large‐Scale Sediment Transport Dynamics with Multibeam Sonar

Abstract

Multibeam Echo‐Sounder (MBES) systems have developed rapidly over recent decades and are routinely deployed to provide high‐resolution bathymetric imaging. Modern data handling and storage technologies have facilitated the logging of the back‐scatter information previously discarded by these systems. This paper develops a novel methodology to exploit this logging capability to quantify the concentration and dynamics of suspended sediment within the water column. This development provides a multi‐purpose tool for the holistic surveying of sediment transport by imaging suspended sediment concentration, associated flow structures and providing concurrent high‐resolution bathymetry. This paper presents the results obtained from the deployment a RESON 7125 MBES in the field, with the aim of examining the dynamics of suspended sediment transport over dune bedforms and in the region of flow mixing between large rivers of significantly different suspended sediment concentration. Results from controlled tank tests are also presented, obtained using different types and mixes of sediment. The results demonstrate the capability of MBES systems to successfully resolve the contrast in suspended sediment concentrations. The large sets of data recorded in the two‐dimensional MBES swath enables the real‐time monitoring of suspended sediment transport and related flow processes on a scale previously unrealisable with single‐beam acoustic systems.