Study on Critical Conditions of Scour-and-Siltation in Flood Seasons of Ningmeng Reach in the Upper Yellow River

Based on the actual measurement datum in flood seasons in the Ningmeng Reach of the Upper Yellow River Reach, Authors search the law of erosion and deposition and sediment transport characteristics with built the quantitative correlation of erosion and deposition efficiency and water and sediment combination (sediment coming coefficient, sediment concentration/discharge)of the flood season. When the sediment coming coefficients of flood season is0.0038kg.s/m6 the Ningmeng reach in relative equilibrium state. The Ningmeng reach has the characteristic of “the more sediment coming, the more depositing, the more sediment transporting”, the sediment discharge increases with sediment concentration of coming flow increasing. The result of these research can be used in the Yellow River management and alluvial channel regulation.