25 April 2012

Increasing landslide hazards and the Three Gorges Dam

Posted by Dave Petley

A couple of weeks ago I posted several images from my recent visit to China Three Gorges University, and in particular on landslides on the banks of the reservoir associated with the Three Gorges Dam.  Interestingly, last week, whilst I was on vacation, a number of news agencies ran a story about landslide hazards in this area.  The spur appears to have been an interview on China National Radio with an official, Liu Yuan, from the Ministry of Land Resources .  According to the CRI English report, Liu Yuan indicated that up to 100,000 people living on the banks of the reservoir will need to be relocated over the next three to five years as a result of landslides and bank collapses.  The news report notes that he stated that:

“The prospect of controlling or preventing geological disasters in the near future was not promising”

Perhaps most interesting is that Liu Yuan stated that (in the words of the report):

“After the water levels were raised, there were 70 percent more landslides and bank collapses in the area than had been predicted…[and]… an increasing number of monitoring sites were seeing adverse effects from the maximum water level.

Liu indicated that management of rockfalls and landslides is needed at 335 sites, and that there is a need to monitor 5,386 dangerous locations.

Landslides were identified as being a major hazard of the Three Gorges project more than a decade ago, and several years ago I wrote that although a Vaiont style event was unlikely, landslides would probably be a major problem.  To give an indication of the concerns, the image below is the Qianjinangping landslide, which I visited on my recent trip.  It occurred as the water level was being raised in July 2003.  The landslide killed 24 people, destroyed 346 houses and caused the loss of four factories.

Interestingly, the loss of life consisted of 13 people on the slope and 11 fishermen, who were hit by the displacement wave.  This is believed to have been up to 30 m high.