antidunes are typically found in fluvial environments in shallow areas with a high flow rate. unlike ripples and dunes in lower flow regime, antidunes are generally symmetric and migrate counter to the flow direction. antidunes evolve rapidly, growing in amplitude as they migrate against the current. when the surface wave above them becomes unstable and breaks (when the surface wave amplitude reaches 1/7 its wavelength) most of the antidune bedform is destroyed and its sediment carried down stream.