Three-dimensional hydrodynamic modelling of inland marine waters of Washington State, United States, for tidal resource and environmental impact assessment

Inland coastal waters of the State of Washington, United States, are fjord-like in character and feature passages where tidal currents with speeds of 3 m/s or greater occur. Combined with close proximity to the major metropolitan area of Seattle and easy access to the power grid, the region is a prime candidate within the United States for tidal power generation. A new three-dimensional (3D) model of tidal circulation of these waters has been implemented. The model is based on Stanford University's SUNTANS code, and covers the eastern Strait of Juan de Fuca, Puget Sound, San Juan and Channel Islands, and the southern Georgia Basin with an unstructured triangular mesh of 250 m average resolution. It is forced with tidal currents from a regional tidal model along open boundaries. Barotropic tidal response is calibrated against compiled tidal data for the region; the system response is characterised in terms of sea surface height variability and energy dissipation. The model can simulate tides with quantitative accuracy within Puget Sound, but it over-predicts tidal range and under-predicts currents in the waterways leading up to the Main Basin of the Sound. Future plans for the model include extension of the model domain for the entire Georgia Basin, incorporation of partial bottom cells and baroclinic processes and improvements in bathymetry.