Analysis of Scour Trend of the Riverbed in the Lower Yellow River

After the construction of reservoirs at the middle reaches of the Yellow River main stream, the downstream river will generally undergo a sediment scour. During the operation of the Xiaolangdi Reservoir from October 1999 to April 2018, the accumulated sediment scour quantity reached 2.98 billion tons at lower reaches. At present, Xiaolangdi Reservoir is in its first stage of the late sediment storage period, and the reservoir will keep storing sediment, which will lead to further sediment scour at lower reaches. Based on the data measured at Sanmenxia and Xiaolangdi reservoirs, the variation about sediment scour at lower reaches after the reservoirs were put into operation was analyzed. It shows that the closer to the dam is, the larger the sediment scour intensity (sediment scour quantity per unit river length) is, the decline in water level under the same discharge gradually decreases from the upper to lower along the river, the water surface slope at the river becomes small, and the bed material becomes coarsened. Through the calculation with the mathematical model for water and sediment, the future potential maximum depth of sediment scour in the river bed at lower reaches is predicted and the maximum depth of sediment scour along the section from Huayuankou to Lijin(lower reaches of the Yellow River) river reach since 2000 is promoted as 5.01m~2.09m. The research results can provide reference for the construction and reconstruction of the projects involved in lower reaches of the Yellow River.