The Hydraulics of Deception Pass

The Salish Sea is a dynamic, complex, and spatially-variable estuary characterized by strong currents. The region is experiencing significant environmental impacts due to ocean acidification, hypoxia and nutrient pollution. As Puget Sound is also a major hub for both recreational and commercial interests, the accurate prediction of tidal currents is critically important for safe and efficient marine navigation. To assure safe and efficient navigation, the NOAA National Ocean Service’s Center for Operational Oceanographic Products and Services (CO-OPS) deployed 135 acoustic Doppler current profilers (ADCPs) in the summers of 2015, 2016 and 2017. Within this study area, Deception Pass stands out as being of particular interest. Deception Pass is a tidal strait that connects Skagit Bay with the Strait of Juan de Fuca. It is known for powerful currents (up to 5 m/s) and hydraulically-driven flows. In this study, observations from the current profiler deployed in Deception Pass and a nearby water level station are analyzed to describe the circulation of the strait. Results will be compared with harmonically-analyzed tidal current predictions to determine the most appropriate method for generating predictions. This data set provides a unique opportunity to use long-term ADCP observations to describe complex systems in energetic estuarine environments. The results of this study could be applied to other hydraulic channels, such as the East River in New York and the Cape Cod Canal in Massachusetts. A deeper understanding of the physics in this strait will provide accurate velocity predictions to aid navigation through this perilous pass, and will support the development and validation of hydrodynamic models of Puget Sound.