Recent flood disasters in China

In 1996 and 1998 several devastating floods occurred on the Yangtze, Yellow, Haihe and Songhua Rivers in China. Flood disasters are now happening more frequently than in the past, due to the fact that economic development is changing the river discharge and the flood control system has not matched the change. In recent years it has been found that small floods cause high stage and extreme damage on the Yellow and Yangtze Rivers, which is due to the non-integrated water and sediment management. On the Yellow River a flood in 1996 with a return period of two years caused the highest recorded stage in history and resulted in huge economic losses because the high rate of siltation and the increasing water diversion from the river had greatly reduced the flood discharge capacity of the river channel. In the Haihe River basin a 1-in-50-year flood in 1996 claimed fewer lives and less damage than in earlier times thanks to artificial drainage canals built in the 1960s and 1970s, which increased the capacity of the drainage system tenfold. New problems arise, however, because due to sediment carried by the tidal current from the sea, the channel outlets are congesting. On the Yangtze River an extreme flood occurred in 1998 which resulted in serious flood damage and affected 8 million people. It was primarily a result of abnormal heavy rainfall, but the flood stage was extremely high due to a reduced flood diversion, reduced regulation capacity of riparian lakes, and channel sedimentation. This paper describes recent flood events and discusses new strategies for flood control.