Seasonal and tidal variations of sediment transport patterns in the Saint John Inner Harbour

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University of New Brunswick


The Saint John Harbour is located along the Bay of Fundy in southern New Brunswick and serves as the primary outlet for the Saint John River. Sediment movement within the Saint John Harbour is a concern from both an ecological and operational perspective. Seasonal measurements of current velocity and suspended sediment concentration (SSC) have been obtained by deploying two acoustic Doppler current profilers (ADCPs) in the inner harbour. ADCP observations spanned several months and were nearly continuous, thus allowing for an in-depth analysis of meteorological and tidal influences on observed hydrodynamics. A comparative assessment was conducted for spring and neap tides, storm surges, and changes in fluvial input. It was observed at both deployment locations that the intruding salt wedge frequently contained high SSC. The salt wedge is believed to be a major contributor of sediment accretion in the inner harbour, particularly during winter storm surges when river discharge is reduced. The Courtenay Bay Channel was observed to be more sensitive to river level, with only winter storms resulting in a landward average sediment flux. Observations made near Courtenay Bay Channel also suggested the presence of a cross channel flow pattern from an adjacent inter-tidal mudflat. This cross channel flow was only observed during spring freshet conditions and contained high SSC. Hydrodynamic observations from the study were compared with published estuarine theory. Results of the study will help to further define hydrodynamic processes in the Saint John Harbour.