Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
In-River Flocculation Processes and the Transport of Suspended Sediment
B.G. Krishnappan, P. Engel and R. Stephens
National Water Research Institute
Abstract
The objective of this FRAP project was to study the transport processes of suspended sediments of the Fraser and
Thompson river systems and to determine the transport functions that are needed to model the sediment and
contaminant transport both in the near-field and far-field regions.
The work carried out under this project so far consisted of field surveys and laboratory investigations. In the field
surveys, the size distributions of the suspended sediment were measured using an immersible laser particle size
analyzer that was assembled at the National Water Research Institute and were compared with the size
distribution of the primary particles. From these comparisons, one can determine the extent of flocculation of the
suspended sediment in different reaches of the river systems. The results showed that the sediment in the
mainstem Fraser, upstream of the Northwood pulp mill was not flocculated while the sediment in the downstream
reach was. The flocculation of the sediment in the downstream reach was attributed to the presence of pulp mill
effluents.
The size distribution data also showed that the flow conditions in the river played a major role in determining
size of flocs. The role of the hydrodynamics on the flocculation process was investigated in the laboratory using
the rotating circular flume of the National Water Research Institute. The flume experiments shed new light on
the transport characteristics of the fine sediments of the Fraser and Thompson river systems and allowed
formulation of a new sediment transport algorithm that can be incorporated in the far-field food chain and bioaccumulation
model and the near-field plume interaction model that are being developed for the Fraser River
Action Plan.
The present study extends only up to Mission and does not include the estuary region. The sediment behaviour in
the estuary could be very different from that observed in the present study because of the saltwater intrusion and
the tidal effects. These effects have to be quantified in order to extend the models into the estuary regions.
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