The effect of increased bottom friction due to wind-wave current interaction on continental shelves is examined with a two-dimensional shallow water numerical model using an adaptation of the Grant and Madsen bottom-boundary layer theory. Under strong tropical cyclones, this theory may break down in very shallow water where the wind-wave amplitudes can become quite large. Since this is a region where the wind-generated waves are particularly likely to be breaking, a wave-breaking criterion is introduced into the bottom friction formulation.