A Study on the Roughness with Extra Fine Sediment 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 mechanism 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. Then the experiment with extra fine sediment flowing smooth, roughness beds was studied. Based on the comparison between the distributions of velocity and the analysis of resistance in the experiment, the results show that resistance of flow may be considerably reduced by the extra fine sediment if the flow boundary is rough. It has the significant value for the flood control and flood prediction.