SPECTRAL ANALYSIS OF SUSPENDED-SEDIMENT CONCENTRATIONS IN AN ESTUARINE BOUNDARY LAYER

We examine high-resolution time series of suspended-sediment concentration profiles obtained using an acoustic backscatter system in an estuarine tidal current. Spectral analysis reveals Kolmogorov scaling in the turbulent fluctuations in suspended sediment concentrations during episodes of significant transport at elevations of up to 20 cm above the bed and over an inertial subrange of frequencies of order 1/s. Using this scaling property, we develop an opportunity first recognized by Soulsby et al. (1984; Cont. Shelf Res. 3:439-454) and propose a new spectral dissipation method for evaluating flow intensity (the friction velocity) from observed suspended-sediment concentrations alone. Estimates from this method agree well with independently obtained values. The spectral dynamics of suspended sediment can thus provide a window on the intensity and structure of near-bed turbulence in complex environmental flows.