Effectiveness of acoustical backscatter measurements from acoustical profilers for estimation of suspended sediment concentration

In this paper the effectiveness of an approach proposed by Deines [1] for conversion of acoustic backscatter to suspended sediment concentration is verified with measurement data carried out in a tidal flat region of the German North Sea. Extensive measurement data using a 1200 kHz Direct Reading Broadband Acoustic Doppler Current Profiler (ADCP) from a moving vessel were considered. Field conditions with water depths varying from 5 to 20m, depth-averaged current velocities up to 1.4m/s and suspended sediment concentration up to 1350mg/l were covered. Acoustical profiling and optical transmission sampling of suspended sediment concentration over the depth were carried out in more than 200 locations. Comparisons between suspended sediment concentration profiles obtained by converting acoustic backscatter and optical transmission sampling were considered to verify the effectiveness of the approach. The effect of various parameters on the resulting suspended sediment concentration was investigated. The agreement between the concentrations obtained on. the basis of optical and acoustical devices is quite good. Considering the reference concentration values at mid-depth, 97% of the results based on the acoustical measurement lie within a factor of 2 with respect to the ones obtained from the optical sampler.