HYDRODYNAMICS AND SEDIMENT CONCENTRATIONS AT WALKER BAY

R.C. Coppoolse, J.S. Schoonees, G.G. Smith, G.P. Mocke

Abstract


A novel and cost-effective technique for measuring sediment concentrations in high energy surf zones, using a helicopter, was developed and applied at Walker Bay, South Africa. Using this technique, which involved an innovatively operated suspended sediment sampler (TASSS), 280 sediment samples and hours of continuous sediment concentration measurements (with a transmissometer) were acquired at several levels. Currents and waves were also measured at several positions along a cross-shore section. The helicopter was also used to successfully survey the nearshore area using a new method. Spectral analysis of wave and concentration data show responses of the sediment concentration to incident and infragravity waves beyond the surf zone, while suspension is seen to be more intermittent in the surf zone. The concentration profiles beyond the surf zone exhibited typical exponential distributions. Reasonable correlation between the TASSS and the transmissometer was found.

Keywords


Walker Bay; sediment concentration; hydrodynamics

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