Impacts of Ship-Induced Waves along Shorelines during Flooding Events

Abstract

Ship-generated waves are often amplified onshore in confined seaways and are associated with several incidents worldwide. Few tools enable modeling the ship waves’ evolution through complex bathymetry. Here, we assess the skill of XBeach’s ship module for simulating the primary wave generated by a moving pressure head. The model was validated for five ships against field observations at three stations across Lake Saint Pierre, the widest section of the St. Lawrence seaway between Quebec City and Montreal. The study was motivated by reported damages caused by a container ship transiting at 17.6 knots, that is, 20% faster than other ships during extreme flooding. Our model predicted that the ship involved in the incident created drawdown (<20 cm) and runup (<15 cm) that was twice as high as slower ships. However, simulating a wide range of water levels and ship speeds shows that the waves would have been larger at lower water levels due to shoaling. Nonetheless, XBeach could model the evolution of the waves’ drawdown as they propagated over several kilometers from the channel.