There is substantial supply of sediments to the Yellow River as the vast areas of arid and semi-arid hilly areas carry eroded silt and feeds the river with its sediments.
The supply of sediments is so intense that the river carries concentrated loads of yellow coloured sediment, giving the river its name. The lower stretch of the river, downstream from Zhengzhou, plagues the area with frequent floods as it flows across a densely populated and cultivated alluvial plain. Areas in proximity to Zhengzhou had been affected by siltation which raises the river bed by an average of 6 to 10 cm annually, increasing the severity of floods and the subsequent rapid filling of the reservoirs behind the dams.Each episode of flood led to the raising of the river channel via siltation, dykes were breached and existing dykes were raised. In 1887, the river topped 20m high levees and drowned people and their crops and a concomitant famine that took the lives of more than 1 million people. In 1960, the San-men Gorge was completed, towering at a height of 122m and more than 900m wide. Its reservoir had been designed to hold back water. There was also a major initiative to plant trees and irrigate vast stretches of the silt plateau in the aim of reducing the amount of silt reaching the Yellow River.
Repeated construction of levees has not prevented the occurrence of catastrophic floods and river course changes. The lower 800km stretch of the Yellow River has repeatedly shifted its course by hundreds of kilometres. With each flood, the people built the levees to greater heights but this is also met with frequent failures of these levees.
Source: The Straits Times, 26th September 2010 Of recent, there had been a series of dams and rivers being constructed to store water meant for flushing the silt away and this is carried out on an annual basis over a 15 to 20 day period. The flushing period takes place every July and reservoir gates would be opened to prevent the drying up of the water flow. Water would be blasted through the gates at speeds ranging between 2,600 and 4,000 cubic metres per second, depending on the amount of silt in each section. The force of the water would then scour the river channel and carry silt for deposition in the sea instead of the river channel. This has enabled the Yellow River to gain depth by an average of 1.5m since the first flushing was undertaken in 2002.
With reference to:
- Hyndman, D. (2006) Natural Hazards and Disasters
- Abott, P.L. (2007) Natural Disaster
- The Straits Times (September 25, 2010). ‘Taming the Yellow River’.
