Modeling shallow water scattering from rippled seabed in the Long Island Sound

A high frequency (HF) AUV-mounted forward-looking sonar deployed in the shallow Long Island Sound recorded acoustic scattering measurements from large bedform ripples. The axis of transmission was horizontal and laterally oblique to the ripple plane, but at wide horizontal aperture, so that broadside scattering from the ripples was believed to be a significant contributor to the scattering return. The effects of the ripples are explored through finite element model evaluation and comparison. In this study, the seafloor ripples are orders of magnitude larger than the acoustic wavelengths used in the survey. In plane and out of plane, scattering effects are considered, as well as the effects of ripple asymmetry. Modeling techniques for dealing with high frequency systems over large physical distances are discussed. [This work was supported by the Office of Naval Research, Littoral Geosciences and Optics.]