Wave Directional Spectra and Wave-Current Interaction in Lake St. Clair

Analysis of wave data obtained from a three-wavestajf array and collected during a 1985 field study on Lake St. Clair revealed, in some cases, significant differences between the wind and wave directions. High-resolution directional spectrum estimates were obtained using an “exact-form” of the Maximum Likelihood Method. The results indicate that the wavefield structure of lakes as small as Lake St. Clair can be very complicated and display significant directional effects. In cases of westerly to southwesterly winds, peak waves were found to propagate at an angle of up to 60° to the wind direction. Bimodal spectra are observed in many conditions. The observed difference between wind and wave directions is explained by models that include the effect of fetch-gradient, bottom topography, and current-induced refraction. The hydraulic/wind-induced current structure in Lake St. Clair is modeled using a two-dimensional hydrodynamic model. Results indicate that most of the observed features are due to wave interaction with the main hydraulic current caused by the St. Clair/Detroit river system flowing through Lake St. Clair.