AbstractIn this work, we carried out a case study of numerical simulations of low-frequency wave motions at the Marina di Carrara Harbor, where field observations have been conducted from 2005 to 2007. The fully nonlinear Boussinesq model, FUNWAVE-TVD, was applied to study the multiscale processes, including wind waves, infragravity waves, vortical eddies, and their potential effects on harbor operations. To reproduce the bound infragravity waves, the model was modified to take into account the second-order correction in wave generation based on weakly nonlinear second-order theory. Model–data comparisons show that the model correctly predicted the wave spectra in the low-frequency band and the overall long-wave energy inside the harbor. Additional numerical experiments, with different input wave characteristics, indicate that the directional spreading and incident wave direction play a role in predicting short waves inside the harbor, but have limited influence on the long-wave energy distribution, especially for the low-frequency band close to the resonant modes of the harbor. The second-order correction produces correctly the infragravity bands bounded with wave groups in the wave generation region. However, it does not modify the resonant modes and their magnitudes likely due to nearly “white” spectral structure, characterized by a nonzero constant power spectral density block or equivalently constant value/intensity of Fourier modes at different frequencies, in either bound or spurious infragravity waves.