China has a vast territory and about 2/3 of the land area has floods with different types and different degree of hazards, except deserts, Gobi and extreme drought regions and high mountain areas. If a slash is drawn from northeast to southwest along the 400mm rainfall isoline, our countries can be divided into two parts, in which the eastern region is the key area for flood control.
In 1870, the Yangtze River suffered from the largest flood in history. According to the investigation, the peak flow rate in Yichang station is 105 000 steres per second; Hongfeng flow in Zhicheng station is 11000 steres per second. The flood mainly came from Jialing river basin. In the early July, there was a long-continued and heavy rain between Jiangsuo jiang river basin and the Three Gorges and then, the heavy rain zone move eastwards slowly. The flood was the biggest flood since 1153. According to statistics, more than 30 counties in Hubei province and 20 counties in Hunan province suffered from severe flood. In addition, the north of Henan, the Chengde city of Hebei province and the lower reaches of the Huai River and the middle and lower reaches of the Liao River also suffered from the flood.
During the flood season in 1998, there were 8 flood peaks in the upstream of the Yangtze River, which encountered the flood in the middle and lower reaches of the Yangtze River, forming great flood in the whole basin. The flood flowed down vigorously and the water overflowed all over the basin. Coupled with the overflow of Songhua River in the northeast and Nenjiang, our whole country, including the most seriously affected areas, which is Jiangxi, Hunan, Hubei, Heilongjiang, a total of 29 provinces and some other municipalities and autonomous regions have suffered the unexpected calamities. The disaster affected 223 million people and more than 3000 people died. In addition, 6.85 million houses collapsed, more than 2000 hectares of land were submerged and caused economic loss of more than 255.1 billion yuan.
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