Abstract

The history of China is the tale of the Yellow River, Huanghe. The basic characteristics of the river are the low runoff of water and the high concentration of sediment. This disequilibrium is the source of the problem, which causes sedimentation and a rising bed of the lower Huanghe, gradually making it a hanging river, and causing frequent floods, avulsions and di­versions. The water mainly comes from above Lanzhou, while the sediment originates from the soil erosion in the Loess Plateau. This can be illustrated as a gigantic sandglass, with the upper part collecting the water and silt into the river and the lower bulb delivering these to the vast plain. The coarse particles are clearly identified as the source of sedimentation. Major source areas of coarse sediment coincide well with those where the erosion is most intensive. In any year sediment production is controlled by a few thunderstorms in summer, especially within a 15-20 minute period. The reasons for erosion are simple; over the centuries forests have been cut down, vegetation destroyed by overgrazing, the hillsides overworked by the hoe and not terraced to slow down the runoff of summer rains. 

The history of harnessing the Huanghe can be traced back to emperor Yu, who was the first person to succeed in taming the river.  From the Zhangguo period man began to control the river by dikes. Since the Han dynasty the channel of the lower reaches of Huanghe has been broken by natural causes many times and on large scales. This is an inevitable result of the development of the mature stage of the river. The suspended river is the end result of devel­opment and it cannot be retrieved by manpower. Ancient Chinese scientists were concerned mainly with the problems in the river’s lower reaches; river dredging, floodwater diversion and retention, establishment of a levée system and increasing the silt-carrying capacity. Today there is an overall plan for the upper, middle and lower reaches. In the Loess Plateau water and soil conservation works are the most efficient methods. In the lower reaches there are two ways to go in flood prevention, because the dikes cannot be heightened indefinitely; 1) to build a new channel, 2) to maintain the status quo. The latter includes improved efforts to in­crease the capacity of flood and sediment discharges. The long-term perspective is within the reach of 50 to 100 years. 

The problems of flooding are affected by many factors. Therefore a single measure may not satisfy the overall solution of flood control. To solve the problems of sedimentation of the Huanghe, a policy involving a variety of measures for comprehensive control needs to be adopted.  

Keywords: Huanghe, erosion, flood control