Acoustic measurements of boundary layer flow and sediment flux

Results are reported on an assessment of the application of coherent Dopple r and cross-correlation techniques to measure nearbed boundary layer flow. The approaches use acoustic backscattering from sediments entrained into th e water column from the bed, to obtain high-resolution profiles of the near bed hydrodynamics. Measurements are presented from a wave tunnel experiment in which sediment was entrained by unidirectional, oscillatory, and combin ed flows. The data collected have been used to evaluate the capability of t he two flow techniques to measure boundary layer mean, turbulent, and intra wave velocity profiles. Further, the backscattered signal has been used to measure suspended sediment concentration profiles, which have been combined with the velocity profiles to obtain high-resolution measurements of bound ary layer sediment flux. (C) 2000 Acoustical Society of America. [S0001-496 6(00)03609-2].