9 September 2008

Updated: A flow slide disaster in China

Posted by Dave Petley

UPDATED: New image of the site added
UPDATED: Google Earth image of location added.

Update: This image from http://aboutxinjiang.com/ shows the site of the failure. This confirms both the magnitude of the event and the type.

This has been a terrible week for landslide disasters. Sadly, news emerged yesterday of yet another, this time in Taoshi township, Linfen County in Shaanxi province. I think that I have managed to identify the location – see Google Earth image below (location is 35°54′ N, 111°30′ E). Initial reports suggested that 26 people had been killed; this has now been increased to 34, but it seems likely that the death toll is much higher.

Details are a little sketchy at the moment, but the suggestion appear to be that heavy rain caused a tailings dam to fail, releasing a large amount of material that swept as a debris flow down the valley. Xinhua has a limited commentary but a rather interesting set of images of the disaster:

The Xinhua report states that The mud-rock flow … destroyed a three-story office building, a market and some villagers’ houses in the valley. Witness said the flow roared down the valley and washed away the market and the houses in a few minutes.”

The description and images of the landslide suggest that this was what is termed a flowslide – this is a large volume debris flow consisting of soil, rock and water. They are able to move exceptionally fast and to travel large distances. Sadly the mining industry has a terrible record of flowslides originating from spoil heaps or the failure of tailings dams. Examples include:

There is a full if rather horrifying list of these events here. In most more developed countries the accidents at Aberfan, Buffalo Creek and Stava have meant that mine dumps are very tightly regulated, meaning that the accident rate is now low. The impact of not doing so are graphically illustrated by this pair of images (see this web page) of the Stava event in Italy (click on the image for a better view):

Here, 200,000 cubic metres of fluorite tailings flowed over 4 km downstream at over 90 km/h.