Giant prehistoric landslide dammed Yangtze River and could happen again

April 28, 2014
Earth, Energy & Environment

A study has, for the first time, established that a giant landslide blocked China's Yangtze River some 30,000 years ago and that crucially it could happen again with potentially devastating consequences to the local area.

The study, led by researchers at The University of Nottingham Ningbo China (UNNC), is the first to detect and analyse evidence that the Yangtze was blocked by one of the largest-ever recorded landslides.

The landslide, which would have been triggered by a large earthquake not unlike those seen recently in the area, caused a 200 metre dam to form in the river and 100 kilometres of water to 'pond' behind the dam. This huge amount of water would have eventually broken the dam and been released at high speed into the valley, causing widespread flooding.

At the time the area, which is near the present day town of Qiaojia in China's Yunnan province, would have been unhabituated by humans. It is now home to 500,000 people and the site of the new Beihatan Dam, which is currently being constructed in a gorge section downstream of Qiaojia. Once completed it will be the third largest hydropower project in the world.

According to the study's lead author Professor David Higgitt, from UNNC's Department of Geographical Sciences, the findings are important in making developers aware of the potential hazards in the area, especially with regards large construction projects such as the Beihatan Dam.

Professor Higgitt said: "The natural damming of rivers by landslides is a significant hazard in the seismically active, mountainous terrain of Southwest China.

"The findings of this study are significant not only due to the huge dimensions of the landslide but because of the enormous area impounded by the dam and recognition that a river as large as the Yangtze has been – and can be – impacted by persistent river-blocking landslides.

"The presence of the new reservoir introduces the additional hazard of earthquake-generated landslides causing displacement waves, where landslides fall into a reservoir and cause flooding over a dam, often with devastating consequences to the surrounding area. "The need for vigilance in assessing seismic and slope stability hazards in the area is crucial." The study, Giant palaeo-landslide dammed the Yangtze River, is published in Geoscience Letters 2014.

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