Sedimentation patterns and inferred dynamics in Saint John Harbour

This research examines the hydrodynamics and sedimentation within Saint John Harbour, New Brunswick, as part of a collaborative project between the Saint John Port Authority and the University of New Brunswick. In a context of high tidal currents interacting with high river outflow, annual dredging is necessary to maintain the Harbour's activity because of resulting net deposition in some of the harbour basins. To explain this phenomenon, samples of both suspended sediments and bed load sediments were taken in different parts of the Harbour and the Saint John River. The results showed that the tide penetrates the Harbour by forming a salt wedge that glides under the brackish water of the Port. Sediments trapped in the salt wedge deposit in the Harbour, the larger ones being deposited at the entrance of the Courtenay Bay Channel where the flow decreases and the finer ones at the end of the channel. The deposited bottom sediments were found to be mainly composed of quartz and muscovite and the suspended sediment was composed of organic silica, quartz, muscovite and biotite. The compositions of the Inner Harbour sediments were different than those of river and Outer Harbour sediments; the definitive origin of the sediments could not be determined from this project alone. The results of this research will be integrated into a complete hydraulic model of the Port.