Simultaneous measurements of high resolution vertical and horizontal flow profiles and suspended sediments using acoustic backscattering

Acoustic backscatter systems have many advantages in suspended sediment studies, in particular they are non intrusive, and are capable of giving profile measurements with high temporal and spatial resolution. In the present work, which was conducted in an estuary, further advances have enabled the use of high resolution coherent Doppler current profilers to measure the vertical and horizontal flow structure, and acoustic correlation techniques have been developed to measure vertical profiles of horizontal velocities. Typically the measurements from the Doppler systems gave results at sampling frequencies up to 16 Hz, over ranges of the order of a metre with centimetric resolution. In this work the data from the correlation method was only used to derive mean flow. Further work will be carried out to determine the upper frequency limit of the method which will depend on the decorrelation time between the backscattered signals. The acoustic backscatter signals from the systems have been converted to provide suspension concentration profiles and combined with the flow measurements to provide a more complete description of the dynamics of the interactions between the water and sediment, and the structural dimensions