10 April 2012
The Xintan landslide is located on the opposite bank from the Chain Cliff landslide about which I posted yesterday. This catastrophic landslide event occurred on 12th June 1985, destroying the village of Xintan in the process. Fortunately the landslide had been anticipated, and the town evacuated, such that there was no loss of life. The landslide is described in an article by Keqiang et al. 2010 which is available online.
This image shows the landslide site as it is now – of course the lower portions of it are now flooded by the Three Gorges reservoir. unfortunately it was a very hazy day when I was there, so apologies for the quality of the image:
The mechanism of the landslide is quite interesting. The cause was coal mining activity on the lower part of the bluffs above the landslide (located to the left as seen in the photograph above). This destabilised the cliffs, causing repeated rockfalls onto the main slide below. Instability was recognised in the 1970s and the landslide was being monitored as a result. The final failure event does not seem to have been initiated by a rockfall event, but developed progressively over a period of some weeks. Monitoring of the landslide mass detected this development of failure, and on the day before the landslide all 1371 people living in the town were evacuated.
The final failure event was catastrophic, with a mass of about 13 million cubic metres slipping with an average depth of about 45 metres. About 2 million cubic metres entered the main channel of the Yangtze River, generating a wave that was up to 49 m high. The wave killed ten people on the river and destroyed 77 boats.
The landslide is an example of successful monitoring of slope failure – undoubtedly without the evacuation there would have been a substantial loss of life. The slope is now more stable than before, but the potential for further movement remains. Thus, the landslide is still monitored intensively.
Keqiang, He et al. 2010. Dynamic features and effects of rainfall on landslides in the Three Gorges Reservoir region, China: using the Xintan landslide and the large Huangya landslide as the examples. Environmental Earth Sciences, 2(4), 76-1274.