Extreme wave statistics within the Mouth of the Columbia River

Abstract

Rogue waves have presented unpredictable, dire hazards to mariners since the dawn of seafaring. Even in benign seas, isolated rogue waves can severely endanger ships and crews, even accounting for their disappearance. Better understanding of rogue wave generation will enhance safety of maritime operations. This study examines surface height data from wave resolving drifters (WRDs) deployed in groups of 30–50 in the Mouth of the Columbia River (MCR) during the peak of ebb tide in May and June of 2013. Over three separate collection days, effects of opposing currents and bathymetry on swell and wind waves were analyzed as WRDs headed to sea from the MCR. Wave significance was identified based on the local sea state within 1 km of the drifter location. Wave height histograms were calculated from regional wave ensembles and compared with the theoretical Rayleigh distribution of a narrow band, Gaussian wave field. Generally, wave height data in the MCR follow Rayleigh distribution well. Areas over shallower bathymetry of the MCR Bar and predominant waves from the west create intense sea state amplification and rogue wave occurrence, and right-tail deviation from the Rayleigh pdf. Isolated extreme waves and trains of large waves were observed on the Bar.