Internal wave beams are generated by tidal flow over topography. For supercritical topography the beams are narrower and higher harmonic beams more pronounced than for subcritical topography. Numerical simulations show that nonlinear interactions between two topographically generated beams generate internal wave beams with the sum and difference frequencies, significantly modifying the super-tidal frequency portion of the internal wave field in the vicinity of supercritical topographic features.