Experimental study on influences of sediment-laden flow with wide sediment concentration range on channel metamorphosis

River metamorphosis caused by river regime is one of the most important issues in fluvial geomorphology.In this issue,Schumm has proposed a famous qualitative relation.But the relation is quite different in China when it is applied to hyper-concentrated flows.To resolve this controversy,a process-response model experiment using secondary deposited loess with the median diameter of about 0.042mm as well as with a wide sediment concentration range conducted in an 11m×3m flume.The experimental results show that sediment-laden flows with the different sediment concentrations have different behaviors in fill-scour and the ways of channel adjustment.Because of the existence of the hyper-concentrated flow,the sediment-laden flow needs less energy dissipation to transport sediment.Therefore,the variations of the channel form exhibit complex relations with those of the sediment concentration.When the sediment concentration is low,the ratio of the width to the depth of the channel will increase and when it increases to a certain degree to the field of hyper-concentrated flow,the width-to-depth ratio will decrease with the increase of sediment concentration.So does the sinuosity.Thus,according to the experimental results and some case studies about the range of non-hyper-concentrated flow in China,Schumm's relation is correct and available,but to hyper-concentrated flow,Schumm's relation should be modified.