The Yellow River in China is famous for its rich sediment. Ancient books in China recorded that "the Yellow River fights for water, and mud ranks seventh". According to the analysis of modern measured data, the average annual sediment transport in the main stream of the Yellow River is 65.438+0.6 billion tons, and the sediment concentration is 35 kg/m3.
The Yellow River has the highest sediment concentration in the world. Since 1970s, due to the progress of soil and water conservation, the amount of incoming sediment has a decreasing trend. About 70% of the Yellow River Basin is the Loess Plateau, and its surface is covered with tens to hundreds of meters of loess. Loose soil, low erosion resistance, easy to collapse when it meets water.
Although the annual precipitation in the Loess Plateau is only 400 ~ 500mm, the rainfall is concentrated and the rainstorm intensity is high. Geological and climatic characteristics have caused serious soil erosion, which is the root of sediment in the Yellow River.
The sediment of the Yellow River is not only deposited on the downstream riverbed, but also on the Ningmeng reach of the middle reaches of the Yellow River. Ordos Plateau in Ningmeng reach is a rainstorm-prone area in the middle reaches of the Yellow River.
Every rainy season, it often rains heavily here, and floods directly rush into the Yellow River with a large amount of sediment, silting up the riverbed, forcing the main stream of the Yellow River to move northward, directly threatening baotou-lanzhou railway and highways, and doing great harm.
Vegetation and soil erosion in different areas of the Yellow River Basin are very different, while heavy rains are often concentrated in a small area, and the sediment yield per unit area is often significantly different.
Small tributaries living in the middle reaches of the river basin may have the phenomenon that the flood peak in Sha Feng is small, or the flood peak with large flood peak and small sand peak is out of sync with that in Sha Feng. At stations with large control basin area, the incoming water and sediment pass through a long river section for adjustment, and the flood peak is synchronized with Sha Feng.