CONSTRAINING ACOUSTIC BACKSCATTER ESTIMATES OF SUSPENDED SEDIMENT CONCENTRATION PROFILES USING THE BED ECHO

The application of acoustic backscattering to the measurement of suspe nded sediment transport is being increasingly employed. This is due to the unique property of acoustics being able to measure profiles using a single instrument. Also the profiles can readily be obtained with a high spatial and temporal resolution, and this is beginning to provid e detailed images of suspended sediments which have the potential to s ignificantly advance our understanding of suspension processes. Howeve r, at periods of high concentration, when sound attenuation due to sed iment scattering becomes significant, the inversion technique used to obtain the suspended sediment profiles, can, due to relatively small e rrors similar to 5%-10%, generate unbounded concentration profiles whi ch diverge to infinity or zero. Therefore at the periods of greatest s cientific interest, the acoustic technique can encounter difficulties. In the present work the bed echo is utilized to identify the input er rors, and constrain the calculated concentration profiles, and therefo re enable acoustics to play a useful role at high concentration levels . (C) 1995 Acoustical Society of America.