Nearly all rivers to the south of the levee-protected channel drain into the Huai River system, while those to its north into the Hai River system. The most challenging engineering aspect of taming the Yellow River is without doubt the control of the exceptionally high sediment load that the river carries in its lower reaches, averaging 37 kg of sediment per cu m of water at the present time. An average of 1.6 billion tons of sediment enters the river channel at Zhengzhou annually, of which about 1.2 billion tons is carried out to sea, leaving behind a substantial amount to contribute to the silting of the river channel. Throughout history much of the river management effort had been devoted to improving the flood prevention capability of the levee-lined channel, with notable success in the period from 200 to 800 A.D. when the channel was kept to its course. But, keeping pace with an ever-rising channel bed was no easy task, and the protection offered by levees could at best be haphazard, especially at times of war.
Historical records indicate a progressively frequent levee breaching in the last ten centuries.
During such breaches, the flood water would rush onto the surrounding lands, not only inundating farmland and communities, but also taking over existing river channels. The devastated areas would be totally transformed even after the damaged levee sections were repaired and closed, flood water drained, and the river returned to its original channel. Such devastation caused untold human suffering , and Yellow River gained the unenviable distinction as China's Sorrow. Records indicate that the river's levees were breached more than 1,500 times and its course changed 26 times in the last three millennia. A major course change taking place in 1194 A.D. was probably the most devastating economically.