The research of mechanism of constructing riverbed and index of flow and sediment of floodwater in the Lower Yellow River

Abstract

Using the methods of field data analyses and theoretical study, the mechanism of constructing riverbed and index of flow and sediment of floodwater is researched in the Lower Yellow River. The results show that floodwater exert transporting sediment and constructing riverbed adequately, it can lower flood peak and store floodwater and aggrade floodplain and scour channel. The overflowing floodwater can be divided into three phases. In earlier phase, the floodplain aggradation and channel scour has not been exhibited; in metaphase, flow and sediment exchange of the floodplain and channel is sufficient, the floodplain aggradation and channel scour effect is good; in anaphase, the floodplain aggradation and channel scour slower. Synthesis considering riverbed evolvement and the security of floodplain, the controlling indexes are the overflowing parameter 1.4 γ p <0.028. At present, the bankfull discharge of the Lower Yellow River resume 4000 m3/s, in favor of figuring and maintaining logical size of channel, through the controlling of Xiaolangdi reservoir, the peak discharge of ejective floodwater should be 5600-6000 m3/s, the incoming sediment coefficient should be less than 0.028. If controlling floodwater can not overflowing, the peak discharge of ejective floodwater should be 3500-4000 m3/s approaching the bankfull discharge.