Modelling the estuarine circulation of the port of Saint John: Applications in hydrographic surveying

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A 3D baroclinic hydrodynamic model has been developed to investigate the estuarine circulation within the Port of Saint John, in southern New Brunswick. The model simulates the movement and interaction between fresh waters from the Saint John River and saline waters from the Bay of Fundy over four seasonal periods of river flood stages. An improved understanding of sediment dynamics in the harbour is established from the model output, which is critical for understanding the sources of sedimentation and prediction of dredge requirements. The model describes both the longitudinal and lateral estuarine flow within the harbour. This allows for improved estimates of sediment flux through the primary channels, which reveals annual variations in the relative contributions of the river and salt wedge borne sediments to harbour sedimentation rates. Integration of the near seabed flow patterns over a tidal cycle explains regions of deposition and erosion of fine grained sediments and corridors of sediment motion through examination of the residual current velocity fields. The model simulation periods coincide with a dense physical oceanographic observation campaign. The validity of the model output has been verified through statistical comparison to the physical observation data. An innovative practical application of the model output to the assessment and prediction of hydrographic multibeam echosounder depth uncertainty is also examined.