Why did this hazard happen? Here are some major factors:
WEAK PREVENTION ENVIRONMENT
1) People in the upper course of Changjiang, such as Sichuan Province, cut down trees for fuel and timber continuously. They has been living on deforestation since decades ago and until now. The forest area has decreased to 13% only. Without the plant roots' protection, the soil lost rapidly and caused a lot of troubles. Firstly, the water quality in Changjiang has worsen and the riverbed has risen year by year (i.e. silting). Also, there were more floods and landslides when heavy rainfall came. Thus, when such a huge rainfall came from late June to August in 1998, a huge flooding came.
2) In Jiangxi Province, people reclaimed lots of land from the coast of Changjiang and most of the lakes along Changjiang. Man-induced soil losing, which was caused by over-developments. Comparing with half a century ago, Changjiang's riverbed has risen by 1 to 3, or even 4 metres; Poyanghu's (¾I¶§´ò) area has reduced from 5040 km2 to 3950 km2; and Dongtinghu's (¬}®x´ò) area has reduced from 4350 km2 to 2691km2. Those human activities caused the lakes along Changjiang to weaken their ability of controlling the water flow, and so the middle and lower course of Changjiang could not afford huge water flows (i.e. flooding). Thus these regions were most affected when the flooding came in 1998, especially Jiangxi Province and Hubei Province.
3) There was one special feature in the 1998 Changjiang flooding. That was, the cities were mostly affected, like Jingdezhen (´º¼wÂí) in Jiangxi. This large-scale 'city-floods' exposed the problem --- those cities were totally lacking in preventing the floods. The related local governments had seldom cared about this respect and had not prohibited the deforestation and reclamation. They started prevent the flood so late because they had not been affected by most of the floods before and had few money to do so. Thus when this huge flood came in 1998, the local governments could do nothing but try their best to save lives by moving them elsewhere.
4) The Changjiang runs across the middle of China, generally from west to east. It has many tributaries, like Hanjiang (º~¦¿), Minjiang(©¢¦¿), Jingjiang (¯ð¦¿) and so on. Changjiang carries a large volume of water, especially in summer, as the monsoon from Pacific Ocean brings large rainfall to the whole river basin. Lastly, the Changjiang river basin has a low relief. These are the major physical environment features, which increase the risk of flooding in Changjiang.
Besides the nature, human activities also produce a negative factor to flooding. People settle densely along Changjiang from over two millenniums ago till now. This causes the bad drainage system in those regions, as the ancient Chinese even did not know how to build a good drainage system. Moreover, more and more wastes are poured into Changjiang, so that the river becomes shallower. Lastly, the termites living along the river sometimes damage the dams. This left the dams an underlying problem.
5) The last reason of this huge flood's occurrence is the abnormal rainfall. Since the winter in 1997, an unusually large-scale and strong precipitation began to occur in the Changjiang river basin, especially in the upper and middle course. This made the tributaries, ponds and reservoirs along Changjiang to be 'overloaded'. Unfortunately, this heavy rainfall was long-lasted, frequent, stead and concentrated. So a huge flooding was unavoidable.
Next page ---> During the flooding
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