Wave Transformation at Pensacola Pass, Florida

Abstract

Time series of wave, mean current, tidal stage, and wind data collected at Perdido Key, Fla. are analyzed to assess the influence of a large, dredged, microtidal inlet with sizeable shoals on the surrounding wave conditions. The relative importance of different wave transformation processes is addressed, with the aim of providing practical guidelines for modeling wave transformation numerically. A monochromatic wave transformation model that includes wave shoaling, diffraction, breaking, and refraction due to both bathymetric gradients and horizontal gradients in tidal currents is tested against the field data. A two-dimensional (2D) (vertically averaged) hydrodynamic model is used to specify the mean flow, which serves as one input to the wave model. The wave model yields wave heights that, on average, compare well with measurements (within 1%, on average), but produces high spatial variation in wave direction, where waves propagate along a contour. Neglect of wind in the model is suggested to be one reason for the scatter evident in comparisons between measured and modeled wave conditions. Wave conditions west of Caucus Shoal, on the west side of Pensacola Pass, are governed primarily by wind and bathymetric control. Tidal currents exert little influence on waves outside of the shoals that flank the inlet.