Alex E. Hay
Dept. of Phys., Memorial Univ. of Newfoundland, St. John's, NF A1B 3X7, Canada
The field of sediment transport measurement using acoustic remote sensing technique is reviewed, summarizing recent advances and possible directions for the future. The focus is on elucidating sediment transport mechanisms in the bottom boundary layer, and particularly on estimating terms in the sediment mass transport equation. A key problem is the inversion of acoustic backscatter profiles to obtain suspended sediment size and concentration. Several fundamental issues are involved: the scattering cross sections of irregular particles; estimating scatterer concentration fluctuations from fluctuations in signal amplitude; the related problem of inversion stability in the presence of fluctuations; the spatial coherence scales of the concentration field; and sediment mass flux estimation. These issues are illustrated with results from measurements made both in the laboratory and in the field. While several of the above issues remain unsolved, the results are nevertheless quite promising, and indicate a bright future for the application of acoustics to the sediment transport measurement problem.