The use of high frequency acoustic backscatter and Doppler measurements to determine sediment concentration and 2D velocity in water

This paper presents work aimed at eventually providing concurrent concentration and two dimensional velocity measurements for a region of water with a resolution suitable for resolving short timescale phenomena of interest in the evaluation of hydraulic interaction with both natural and man made obstructions. The defined objectives of the work are the incorporation of hardware and software processing schemes for developing single dimensional sediment concentration profiles and single dimensional sediment velocity profiles into a system to show the potential for combining and extending these schemes concurrently into two dimensions. The ultimate goal of this and subsequent work is to develop a prototype instrument giving sequenced acoustic images of the transport phenomena occurring within an observation area. A test system has been developed with sediment particle (sand) sizes of around 0.5 mm diameter as the fundamental target. The system geometry provides for a minimum volumetric resolution in the results of around 5 cm³ at ranges of up to 1.10 m. Sediment suspensions have been illuminated by acoustic burst signals of frequency 1 MHz from which backscatter data have been collected