Mechanism for Flood Peak Increase Downstream along the Lower Yellow River

The paper is intended to account for the abnormal phenomenon that a flood peak increases in the Lower Yellow River. The phenomenon has been found to occur several times in the past. There exists a hot controversy over the causes for it. In this paper, research results of the specific case, which happened in August 2004, are presented. After the mechanism for flood peak increase downstream is analyzed, it is concluded that the flood increase downstream is mainly contributed by sharp resistance reduction during high concentrated floods, which includes the reduction in movable - bed resistance and in resistance reduction made by the kind of floods, while additional gradient formed in flood rising period, the changes in the hydraulic factors caused by the forming of a narrow - deep channel, and overbank flow going back to the channel, contributed much less.