For the construction of a rockfill dam in flowing water, caused by river closure or a dam collapse, generally a progressive lateral dumping of stones is considered. The aim of the study of this phenomenon in the hydraulic laboratory at the University of Sherbrooke was to determine an economic procedure for an actual power plant structure and, if possible, to draw some conclusions of general validity.Scale model techniques of river studies are well understood from the application of the laws of similarity of hydraulic flow and of bed load transport. It seems to be more difficult to extrapolate the results from scale model studies of a river closure, because of the uncertainty of extrapolation of some physical factors like turbulence intensity, form coefficient of solid material, friction and inertia forces of dumped particles, and their stability in connection with bottom roughness. The same uncertainty exists also in the extrapolation of the duration of closure for a specific frequency of dumping.