Observations of solitary internal waves near a dock and their impact on navigation

This research is motivated by an incident in the Saguenay Fjord (QC, Canada) that occured in 2019, where a cargo ship collided with a wharf while docking, resulting in minor material damage to both the vessel and the wharf under circumstances that remain unknown. Our hypothesis is that internal solitary waves may have contributed to the ship's unexpected drift. To test this hypothesis, CTDs, ADCPs and an echosounder were deployed during the summer of 2024. The measurements collected revealed the presence of internal waves over a two-week period. These observations show that trains of internal waves impacted the wharf daily and that they appear to be phase-locked with the tidal cycle. Internal waves of a wavelength of 60 m and a period of 40 s were recorded with amplitudes reaching 10 m and wave-induced horizontal currents of 1m.s^-1. These currents are potentially strong enough to affect the maneuverability of a cargo ship during docking. The results of this research could contribute to the improvement of navigation simulators, adding the ability to account for the effects of internal waves on docking maneuvers.