黄河河道萎缩及其对洪水演进的影响

由于近几年黄河来水来沙偏少，下游河道连年断流、高含沙洪滴水频繁发生，造成黄河干、支流下游河槽连年淤积，断面主槽缩窄，滩槽高差减小，过洪能力降低，漫滩流量减小，同流量水位偏高。河道萎缩使漫滩机遇增多，洪峰削减率大，洪水传播时间延长，威胁堤防安全。

Shrinkage of Yellow River Channel and Its Influence on the Flood Transmission

The main stem and branches of the Yellow River are silted continuously in the past years at the lower reaches with side-effects of shrinkage of main channel section, decrease of height dtherence of beach from channel, reduction of flood delivery capacity and discharge of over beach, and rises of water level at same flow discharge, because of less inflow and sediment in recent years in the Yellow River, flow cutoff year by year, and hyper-concentrated flow happened frequenily. Shrinkage of the river channel increases the prob ability of flow over beaches, enlarges the flood peak decrease rate, prolongs the flood transmission, and thus threatens the dyke safty.