黄河下游洪水的泥沙输移特征

研究了黄河下游1950-1960年、1969-1985年144次洪水的泥沙输移特征.结果表明:泥沙输移比(SDR)随场次洪水平均含沙量和平均来沙系数的增大而迅速减小;存在着一个使泥沙的输移比达到最大值的最优洪水流量级(4000m3/s左右);场次洪水泥沙输移比与场次洪水最大含沙量之间存在着负相关,当最大含沙量(C_max)>300kg/m3时,泥沙输移比(SDR)<0.50,说明高含沙洪水的输移比是很低的.上中游不同源区的洪水对下游的SDR有显著的差异.来自河口镇以上清水区洪水的SDR大多数大于0.60;来自多沙细沙区洪水的SDR都大于0.50;来自多沙粗沙区洪水的SDR则小于0.50.黄河下游SDR与来自不同来源区洪水的搭配关系有关,SDR随来自粗泥沙区来沙量比例的增大而增大,达到一个峰值,与之相对应的粗泥沙区沙量百分比为50%;对于细泥沙区来沙量比例而言,情形类似,与SDR峰值相对应的细泥沙区来沙量百分比为40%.

Study on sediment transport in the lower Yellow River during flood period

Based on the data from 144 flood events during the periods 1950-1960 and 1969-1985,this paper deals with sediment transport in the lower Yellow River.The results show that the channel sediment delivery ratio (SDR) decreases with the increases in the event-averaged sediment concentration and the "incoming sediment coefficient" expressed as sediment concentration divided by water discharge.There is an optimal flood discharge of 4000 m³/s,at which the SDR reaches its maximum.The event SDR is negatively correlated with the event maximum sediment concentration C_max;when C_max is larger than 300 kg/m³,the SDR is smaller than 0.50,indicating that the SDR of hyperconcentrated flows is rather low.The SDRs of floods coming from different source areas are different.The floods whose runoff mainly came from the clear water area above Hekouzhen had a SDR larger than 0.60;those from the "fine sediment producing area" had a SDR larger than 0.50;those from the "coarse sediment producing area" had a SDR smaller than 0.50.The SDR of a given flood event is found to be related with the combination of sediment and runoff from different source areas;when the sediment from the coarse sediment producing area made up of 50% of the total,or the sediment from the fine sediment producing area made up of 40% of the total,the SDR of the flood events reached its maximum.