FLOOD PROBLEM OF CHINA’S HUANGO RIVER:
AB Thapa
Scientists had established a long time ago that the Kosi river used to flow about 120 km away to the east from its present position some 200 years ago. There was a gradual lateral shifting of the Kosi channel to the west until it was confined about 50 years ago at its present position between two embankments running parallel on either sides of this river. Scientists had also forecasted that in future the direction of the lateral movement of the Kosi will be reversed. Such lateral movements from west to east, unlike the previous east to west movement, would be accompanied with far greater loss of life and property.
Now in front of our eyes we are seeing that the Kosi has changed its course to the east. The river is flowing through settlements some 1.5 km off the original course. Concerned government officials are saying that given the extent of damage to the embankment, it would be daunting task to bring the river back to its original course.
Similarity between Huango and Kosi
There are two rivers in Asia, which were known in the past as the river of sorrow. The Kosi River that flows from Nepal to India was known as the “ Sorrow of Bihar”, whereas the Huang Ho River in China ( also called the Yellow River) was known as the “Sorrow of China”. Both rivers have similar maximum discharge. These two rivers were named “River of Sorrow” for having caused widespread suffering of a very large population of the country over a long period. At present the Kosi and the Yellow River have nothing in common. The Yellow River is already completely controlled whereas the Kosi still remains totally unregulated.
Highest Priority to Huangho Flood Control
In a recently published article in CHINA DAILY, Xiong Lel writes that the Huang Ho or the Yellow River was a cradle and killer, a mother and menace. From time immemorial, China had both depended on and dreaded this mighty river.
Even during the Qing Dynasty (1644-1911), control of the Yellow River was thought so critical to dynastic stability that a ministerial post – Governor of Yellow River Affairs- was established. The holder, only second in power to the prime minister, could enter the Forbidden City without dismounting
Dubbed “China’s Sorrow” for inflicting one disaster after another, particularly on the heavily populated lower reaches, the river posed a great threat. In the 25 centuries between 602 BC, the fifth year in the reign of King Ding of the Zhou Dynasty, and 1938, the Yellow River breached its dykes no fewer than 1,590 times. In addition, the river’s course to the sea in its lower reaches shifted from time to time Until recently there were on average two breaches every three years , and a major change of course once a century. Each and every one of these events left its toll on local populations, both their lives and property.
Huangho river in its middle reaches passes through a plateau of the fine sediment called loess. When it rains, flash floods literally carry mountains of loess down into the river Over the years, it is said that the sedimentation has raised the riverbed by 5-10 centimeters a year. The Huangho River thus became a “hanging river”
China’s Second Largest River
Huang Ho or Yellow River, is the second largest river in China after the Yangtze, with a total length of 5,464 km. The Yellow River rises in northern China in a series of springs and lakes in the Kunlun Mountains, south of the Gobi Desert
At the city of Kaifeng, the river enters the plains and changes from a torrent to a meandering stream with a broad channel enclosed by dikes. The dikes were built over a period of centuries to control the river and prevent floods, but they have actually had the opposite effect. Because the large amount of sediment carried by the stream has silted up the bottom of the riverbed, the level of the river has risen necessitating the construction of higher and higher dikes As a result, in many portions of the lower course the river is much above the surrounding plain, and when the river water level rises, disastrous floods occur.. The floods of the Yellow River have been so frequent and so devastating that the river is often called China's Sorrow.
River Channel Hydraulics
There are few striking similarity between the Yellow River and the Kosi. Both these rivers are dubbed “ River of Sorrow”. The annual flow of both these rivers are almost equal. The annual flow of the Yellow River is about 58,000 million cubic meters whereas such annual flow of the Kosi at Barahachetra is only slightly less. It is about 51,000 million cubic meters. As far as the geomorphic and hydraulic characterization is concerned, there is hardly any resemblance between these two rivers. The Kosi, in terms of channel pattern, is a braided river whereas the Yellow River is a meandering river. Despite such differences, scientists were virtually unanimous in their opinion that there was only one way to prevent the Yellow River as well as the Kosi flood disasters. The only recourse is the provision of storage dams to control the floods.
Rivers can be characterized in terms of channel pattern. Such channel patterns can be straight, meandering, braided, or some combination of these. A braided river like the Kosi would be relatively wide and it would be having poorly defined unstable banks, and it would be characterized by a steep, shallow water course with multiple channel divisions around alluvial islands. There are two primary causes that may be responsible for the braided condition. (1) the stream may be supplied with more sediment than it can carry resulting in deposition of part of the load, and (2) steep slopes, which produce a wide shallow channel where bars and islands form readily.
A meandering stream such as the Upper Mississippi or the Lower Illinois or the Yellow River is the one whose channel alignment consists principally of pronounced bends, the shapes of which have not been determined predominantly by the varying nature of the terrain through which the channel passes. Alluvial channels of all types deviate from a straight alignment. The thalweg oscillates transversely and initiates the formation of bends. A meandering river, in sharp contrast to the braided river carrying the same mean discharge, would be having far smaller longitudinal slope.
How Yellow River Flood Problem Solved
Since 1949 some eight dams have been built and four more are under construction along its 4,674-kilometre course to control the Yellow River flooding. Among the dams built a long time ago are the dams Liujaxia, Sanmenxia, Longyangxia which were constructed in the years 1968, 1979 and 1988 respectively. It is reported that keeping the Yellow River at bay has saved the China US$ 50 billion as of 1990.
Now China is facing completely a new type of problem. The Yellow River water is excessively used in irrigation, as a result, the river has started to dry up. Very recently China has embarked on a grandiose plan to divert the surplus flow of the Yangtze River to augment the flow of the Yellow River.
