Impact of Channel Shrinkage on Flood Routing along the Lower Yellow River

According to the principles of hydrology and riverbed evolution, the rule of flood routing in the channel shrinkage process was analyzed based on field data and movable - bed model test. The result shows that, no matter how the sediment concentration is, the flood peak reduction ratio will increase and the flattening - out of flood wave will occur in the channel shrinkage process. However, when the flood peak discharge is close to the bank - full discharge, the flood wave transformation is small and so is the flood peak reduction. The advance speed of freshet slowed down and the advance duration prolonged. When the flood peak discharge is about double of the bank - full discharge, the advance speed of the flood reaches its minimum. Even so, the synchronization adjustment relationship still exists between the average velocity and nux of the channel section. The channel shrinkage reduced the wetted cross - sectional area, increased the rising speed rate of the average riverbed elevation, and so increased the rising amplitude of flood stage. After channel shrinkage, the sediment transport by flood still features of " more coming, more silting and more scouring", and the relationship between sediment carrying capacity and main river channel's morphology is still in accordance with the general riverbed evolution rules, and has nothing to do with the channel shrinkage mode.