Discussion of "Characteristics of free overfall for supercritical flows"

It was claimed that the characteristics of free overfall with supercritical inflow conditions were not studied to date. That is incorrect and the Canadian Journal of Civil Engineering published a pertinent study about 10 years ago (Chanson and Toombes 1998). After a review of that study, it will be emphasised that the writers' results must be considered with caution. The supercritical flow at an abrupt drop is strongly three-dimensional and unsteady, and this aspect has direct implications for engineering designs