Environment

Starting to crack

Shanghai struggles with subsidence

The road just collapsed

On the afternoon of April 1, Yang Erjing, a 27 year-old office employee, was returning to her place of work in west Beijing when the pavement suddenly collapsed beneath her, plunging her in to a pit of scalding water.

Yang had sustained 90% burns by the time a female colleague managed to pull her out of the hole. She died on Monday.

“The water came up to her neck. Her skin and flesh were almost separated,” the Beijing News quoted the colleague as saying.

The immediate cause of the “sinkhole” seems have been a ruptured pipe carrying hot water to a nearby residential building.

Yet as the Ministry of Land and Resources admitted in February, at least 79,000 square kilometres of Chinese land has subsided by more than 20cm since modern records began.

The worst affected areas are the Yangtze River Delta where Shanghai is situated, the North China Plain, including the Beijing area, and the provinces of Shanxi and Shaanxi, CCTV reports.

In total, 50 cities across China are literally sinking as you read this.

Subsidence can be greatest around poorly designed water pipes, sewage and subway systems, especially if they are poorly maintained, the report said. According to a 2006 study from China’s Geological Survey, subsidence has cost the country at least Rmb500 billion ($79.3 billion) in damage to infrastructure and land since 1950.

“Land subsidence is a type of regional geological hazard that develops slowly and progresses to a disaster, entailing great losses,” it said.

The report singled out the port cities Shanghai and Tianjin as the two worst affected conurbations, with large parts of Shanghai now two metres lower than in the 1920s, when records began (for perspective, that’s the height of basketballer Kobe Bryant). But Tianjin takes the record, having dropped over 3 metres in parts – meaning that large areas of the municipality are now below sea level.

The report identifies the over-exploitation of groundwater and rapid urbanisation as the main reasons for subsidence. By comparison 44,000 square kilometres of land in the US – a country of similar size to China – is affected by similar problems.

“In Shanghai… subsidence in the downtown area has increased because of large-scale construction work… and also as a consequence of increased loading by about 5,000 new high-rise buildings,” the report says.

Although developers denied it at the time, this is exactly what Shanghai residents feared when an 8-metre crack appeared in the ground around the base of the Shanghai Tower in February.

The tower will be the world’s second highest building when it is completed in 2014. One Shanghai-based news portal wrote up the story under the headline “Shanglantis”, comparing the city to the mythical city of Atlantis, dispatched by the Gods to the bottom of the ocean for its hubris.

But even if Pudong doesn’t end up at the bottom of the Huangpu River, subsidence is taking its toll on many of China’s other flagship projects.

In March, a brand new section of the high-speed rail network in Hubei had to be relaid after an embankment collapsed and 7 kilometres of track were found to have warped.

Sinkholes are also a regular feature of many of China’s newly built highways.

In February the State Council approved a Land Subsidence Prevention Project which envisages limiting the size of buildings in some of the worst affected areas, as well as pumping water back into the ground.

But experts say some types of aquifer cannot be refilled and it is not clear where the extra water will come from, especially as it was a shortage of it that led to groundwater being pumped out in the first place.

In the case of Beijing’s aquifers, the government has proposed that water from the controversial South-North Water Project be used (see WiC139). “This is nonsense,” wrote Sina Weibo user Beijingshanyaodan. “They are simply taking down the east wall to fix the west wall.”


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