Wednesday, May 14, 2008

Should China evacuate the city of Dujiangyan?

The cracks in the Zipingpu Dam above a city inhabited by half a million people are called "extremely dangerous." If this report is correct, surely the residents of the city of Dujiangyan should be warned. Perhaps the whole town should be evacuated. There could be yet be aftershocks and there is no certainty that the 2,000 soldiers sent to repair the dam will succeed. More here.

  • The Times of London has a report on the possibility of the failure of Zipingpu dam, which lies upstream from Dujiangyan:

The Zipingpu dam is among the most modern in China but was built despite warnings it lay close to a major earthquake fault line. Planning for the dam was in its early stages in 2000 when seismologists from China’s Earthquake Bureau warned that it could be at risk.

Earthquake protection would have been built into the design of the dam, which was constructed in an area where 9,000 people died in 1933 amid landslides caused by an earthquake.

Nevertheless, the enormous reservoir has the capacity to hold 1.2 billion cubic metres of water and if it were to collapse the consequences would be disastrous.

“This is a seriously big dam,” said Ian Cluckie, a professor of hydrology and water management at the University of Bristol.

“If it were to go pop it would be absolutely diabolically catastrophically beyond belief.”

There were concerns last night that water levels in the dam were still rising, suggesting that there was some sort of blockage preventing the Chinese authorities from draining it.

“If there’s rising water the normal way of getting water out of the dam isn’t working. They could just have a major problem with this one. About the only thing you can contemplate doing in such circumstances is dropping a load of sand, concrete or soil into it and hoping it fills a crack.”

The article ends by noting that other dams could burst, but adds one hopeful nugget of information with regards to Zipingpu dam: "It was regarded as fortunate that the Zipingpu dam, completed in late 2006, was only about half-full when the earthquake struck because it meant the pressure was much lower than it might have been."

Photo: Zipingpu Dam by Wingchina.

Update #2: According to Sky News, residents of Dujiangyan are not aware of the danger posed by the dam.
Update #3: WSJ has an article on the Zipingpu dam. Apparently, dam experts think that if a dam is going to burst, it is most likely to happen during the earthquake, not afterwards.
Photo 2: WSJ

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