Sediment transport over salt-wedge intrusions: Fraser River estuary, Canada

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ABSTRACT

A field investigation was conducted in the Fraser River estuary, Canada, to examine flow and suspended sediment concentration above salt-wedge intrusions. The thickness of the upper layer above the intrusion decreased with distance seaward of the salt-wedge tip, but salinity and velocity increased. A seaward decline in the suspended sediment concentration of the upper layer is believed to result from interference in the exchange of sediment between the flow and the bed, reduced turbulence, flocculation of fine sediment, and dilution of the sediment-water mixture.

Multiple regression models based on simple physical reasoning and easily obtained data provide relations for the suspended sediment concentration of the upper layer. Scaling the models did not produce notable improvements over the dimensioned results and introduced numerical instability. The models showed that sediment concentration was controlled by riverine processes and that the rate of seaward decline in concentration was exponential. These observations support a descriptive salt-wedge sedimentary model.

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