The generation and trapping of solitary waves over topography

Observations of tidal flow over a sill show that upstream solitary wave gen eration occurred in conjunction with the downstream movement of a streamlin e bifurcation over the obstacle crest. Solitary waves appeared upstream of the bifurcation, riding on the surface stratification. Shear flow instabili ties on the plunging interface were also evident and may contribute to wave generation through subharmonic interaction. Nonlinear waves generated down stream of an internal control became trapped in the supercritical flow.