Basic Concepts and Management Issues of Rivers - River Dynamics and Integrated River Management - page 33

Fig. 1.26 The highest flood discharge of rivers as a function of drainage area in China compared with rivers throughout
the world (after Luo and Luo, 1996)
Not only huge flood but also small flood may cause great loss. Figure 1.28 shows people escaping
from the flooded floodplain of the Yellow River, which is in Henan Province near Zhengzhou, during the
1996 flood. The flood discharge was 7,860 m 3 /s, which was only a 2-year flood. About 2.41 million people
were affected by the flood and 800 million U.S. dollars were lost. The main causes of the high flood
disaster were the abnormal high stage and low conveyance capacity of the channel due to sedimentation.
In the lower reaches the river flood plain is confined between the grand levees of the Yellow River. Rapid
economic development and population growth lead to extensive invasion into the river floodplain. Although
the total amount of annual sediment deposition in the lower Yellow River was reduced, the amount of
sediment deposition in the main channel was increased. Consequently, the channel cross section became
smaller, and the water conveying capacity of the river channel was greatly reduced.
Fig. 1.27 A 100-year flood hit the Wuzhou City in the West River basin in 2005