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The mouth of the Columbia River (MCR) has a longstanding reputation of hazardous navigational conditions. This reputation has been developing since the first ship, the Columbia, traversed through the inlet in 1792. The hazardous conditions are related to the large waves and strong tidal currents that are common in the area. Tidal currents often reach 2 m/s. As large waves interact with strong tidal currents waves can steepen and break. This study investigates on the importance of wave-current interaction at the MCR. To model these conditions a two dimensional spectral model, SWAN (Simulating WAves Nearshore) (Booij, 1999), was used. SWAN simulations were completed neglecting as well as including current to make comparisons. Wave height and length were found to be influenced considerably by wave-current interaction.
The SWAN simulations were also compared to both radar and insitu observations. Radar--estimated and SWAN--predicted wave direction and wave breaking were compared. SWAN-predicted wave direction and radar-observed wave direction compared well; however, poor agreement between observations and predictions occurred over a shoal in the region used to make comparisons. The source of this disagreement is unknown. Radar--observed wave breaking compared well with SWAN-predicted wave breaking in depth-limited cases; however, radar-observations indicate current induced wave breaking that SWAN does not predict. Insitu observations of wave direction and wave height both demonstrated good agreement with SWAN-predicted wave direction and wave height. Overall SWAN-predictions demonstrate good agreement with observations from both radar and insitu measurements. |
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