In a letter submitted to the State Council, Wen Fubo, former director of the Changjiang Water Resources Commission, and Zheng Shouren, current manager of the CWRC’s engineering group, stress that the region is geologically unstable and prone to landslides and riverbank collapses. Potentially dangerous areas must be checked and double-checked in order to protect people and property, they write in the letter, which was reported on the Chinese Academy of Engineering Web site.The massive Three Gorges reservoir, which eventually will stretch for 600 km behind the dam, will affect 5,464 km of shoreline in the main channel of the Yangtze River and its tributaries. A survey last year by the CWRC identified 1,320 potentially dangerous places in the reservoir area, where landslides might occur or sections of riverbank could collapse. According to the survey, these unstable locations contain 3.34 billion cubic metres of rock and earth.

Impounding a huge body of water in the reservoir, which is scheduled to take place next June, is likely to activate at least 760 landslips, the respected experts write. Urgent action needs to be taken near urban areas, which face the threat of 21 potential landslips and 40 km of unstable riverbank.

Construction work now under way on a vast number of new settlements could also trigger geological disasters, they warn. Two cities, 11 county seats, 116 small towns and 6,301 villages are being relocated because of the dam. They say that what worries them most is that almost all of the new settlements are being built in a geologically fragile, mountainous region.

Although no previous dam project in China has included a geological-safety inspection, Mr. Wen and Mr. Zheng argue that the Three Gorges is a special case because of the region’s particular physical conditions. To ensure the safety of people resettled near the reservoir, they say expert teams must be sent in to undertake a careful, scientific appraisal of all the construction projects in the vicinity before the reservoir is filled.

China Daily reported earlier this month that “because of the complicated natural and geological conditions in the reservoir area, more than 70 landslides, collapses, and mud-rock flows have been recorded along its banks since 1982, killing about 400 people.”