Channel shrinkage and its disaster-causing mechanism in the Lower Yellow River

The disaster-causing effect and mechanism of channel shrinkage in the Lower Yellow River are analyzed according to the physical model experiment and field data. The results show that the channel shrinkage is a evolution phenomenon of the decline of flood carrying capacity and sediment transport in the fluvial process of river channel, which leads to the increase of flood frequency and higher flood water level during the same flow discharge. The disaster-causing phenomena include the increase of distorted flow pattern, engineering damage and economic losses in shoal areas, and so on. The increase of the amplitude of the flood water level rising caused by the narrowing of main channel, the raise of mean elevation of the river bed and the elevated datum level at young flood caused by wetted area reduction are the main causes affecting the disaster-causing effect. The disaster-causing effect is dependent on the modes of channel shrinkage, among them the mode with heavy deposition happened to the main channel is the most.