The river's revenge

UNESCO Courier, Nov, 1998 by Xiong Lei

Heavy rainfall led to this year's flooding in China, but years of human error turned it into a national catastrophe

The floods that ravaged the Chang Jiang (Yangtze-Kiang, literally the "Long River") basin this year were the most serious since 1954, and flooding in northeast China was the worst in recorded history.

However, compared to the situation in 1954, the volume of water in this year's Yangtze flooding "was not very great", says Lu Qinkan, a former official in China's Ministry of Water Resources who has been monitoring the river since the 1940s. And yet the damage is more serious. Atmospheric physicist Tao Shiyan, a member of the Chinese Academy of Sciences, concludes that unfavourable weather conditions "were not fully responsible" for a disaster which, according to official sources, claimed more than 3,000 lives between June and August this year, affected 223 million persons and almost a quarter of the country's arable land, destroyed nearly five million dwellings, and caused damage costing 166 billion yuan (around $21 billion).

A hefty price tag for neglect

How could such catastrophic flooding have occurred? Lu attributes the problem to the river's inability to release its floodwater efficiently. "The key factor in controlling the Yangtze's floods is overall planning for storage and above all for discharge of floodwaters," he says. "Laid down in the 1950s, it remains a good principle today. Unfortunately the balance has always been skewed in favour of storage behind dams." Now many sections of the dikes and embankments which total 3,570 km in length along the lower and middle reaches of the Yangtze and "are essential to enchance the river's capacity to discharge floodwater" are badly in need of repair. This summer, seepage, cracks, and collapses occurred at thousands of points, showing that the dikes were weak.

Given the length and width of the Yangtze, Lu explains, if the height of the dikes was raised by an average of one metre, an additional 7,500 cubic metres of water could be discharged per second (20 billion cubic metres per month). However, a ten-year plan drawn up in 1980 to heighten and reinforce the Yangtze's dikes has never been fully carried out, Lu adds. If it had, "this year's disaster would have been considerably alleviated."

The water authorities explain that the delay is due to shortage of funds. Whereas 4.8 billion yuan ($1.6 billion at the then rate) were needed to finance 34 projects in 1980, only 399 million yuan had been invested by 1987, and only 12 projects had been launched. One exception is Jiangxi province, the final stage of the river's course before it enters the East China Sea. Authorities there have spent around 7 billion yuan on flood defence work since the early 1990s, about one seventh of it on dikes along the Yangtze.

[TABULAR DATA OMITTED]

But the price of neglect elsewhere has been high. Damage caused by Yangtze flooding in 1995, 1996 and this year has cost at least 200 billion yuan ($25 billion). This sum represents nearly 40 times the budget for the 1980 plan and amounts to two-thirds of the total investment needed for the controversial Three Gorges Dam project. Many engineers believe that this dam, when completed, could help tame the Yangtze floods, but others, including Lu, are sceptical. As an adviser to the expert panel on flood control during the feasibility study carried out in the 1980s, he maintains that the dam's flood control capacity "will only be limited".

Located near Yichang, where the Yangtze emerges from narrow gorges before entering its flatter middle reaches, the dam may help to control upstream floods. But this year's deadly floods were downstream, particularly in Jiangxi, Hunan and Hubei provinces.

With a total storage capacity of 39.3 billion cubic metres, the Three Gorges Reservoir will have a flood control capacity of 22.2 billion cubic metres, Lu says, a figure "that is far exceeded by the river's gross flood volume." He maintains that the Three Gorges Dam attracts massive [TABULAR DATA OMITTED] investment at the expense of basic local flood defence work. Lu Yaoru, a hydrogeologist with the Ministry of Land and Natural Resources, predicts that the dam will result in more downstream sedimentation, which will affect the river's capacity to discharge floodwater.

Hundreds of lost lakes

In fact, says Yu Xiaogan, a senior geographer with the Chinese Academy of Sciences, the river bed in a number of stretches has already risen by 5 to 14 metres above surrounding field levels as a result of sedimentation. "In those sections the Yangtze has already become a hanging river," he says. "And that is very dangerous."

He believes that misuse of riverside land and adjoining lakes have also aggravated the problem. As a result of population pressure, the surface areas of Dongting and Boyang lakes, two of the major detention basins for Yangtze floods, have shrunk by 46 per cent and 40 per cent respectively in the past forty years. Their storage capacity has decreased from more than 30 billion to around 17 billion cubic metres. Hubei, once known as "the province of a thousand lakes", had 1,066 lakes in the late 1950s. Now there are only 182. Consequently, floodwaters that might have been stored in lakes are now inundating cities, towns and fields that occupy dried out land. Whereas the region had 100,000 inhabitants in 1954, 20,000 of whom had to move out when danger threatened, today there are half a million, 330,000 of whom have to be removed when the waters rise.