A Study on the Resistance Reduction of Flows with Hyper-Concentration in Open Channel

In view of the abnormal phenomenon that a flood peak increased in August 2004 and July 2005 along the lower Yellow River, the experiment of this abnormal phenomenon is studied. It is found that the flood increase was due to the decrease the channel roughness in the propagation of high concentrated flood carrying the extra fine sediment which was discharged from xiaolangdi reservoir. Experiments with hyper-concentration flowing over the rough beds prove that the resistance of the flow may be considerably reduced by suspended sediment. Especially in hyper-concentration, the phenomenon of drag-reducing is more obvious. The drag reduction mechanism for the open channel flow with hyper-concentration is revelated. The drag reduction rate in open channel flow of hyper-concentration is presented, and the effects of relevant factors on the drag reduction rate are discussed systematically. It has the significant value for the flood control and flood prediction of hyper-concentration.