ABSTRACT
Fluvial processes associated with hyperconcentrated flow are usually characterized by great and rapid change of aggradation or degradation. Peculiar forms of siltation or erosion associated with hyperconcentrated flow are clogging or ripping up the bottom. Provided the concentration of a hyperconcentrated flow is in the range of 400-1000 kg /m and all the sediment deposites, the discharge at a downstream gauging station will diminish by 29-72% because of the reduction of the volume of settled sediment together with the water in pores between sediment particles. Based on the foregoing facts the following conclusion can be deduced: a hyperconcentrated flow clogs when the shear acting on the boundary equals its corresponding yield stress. The particular phenomenon of 'ripping up the bottom' is described by local witnesses as follow: as the flood passed, a block of the river bed, one meter thick, was torn off by the flow; it turned around and stood up, towering over the water surface for several seconds.
