10 June 2013

A new landslide video showing the transition from a soil slump to a soil slide

Posted by Dave Petley

Many thanks to Graziella Devoli for the heads up on this one

Across Europe in the last few weeks there has been very heavy rainfall, triggering landslides and floods across a wide area.  The most recent event occurred in Switzerland overnight, and Germany is experiencing extensive and very damaging floods as the water moves through the river system.

Starting on 17th May, a band of rain traveled up across Europe from Northern Italy, where it caused widespread flooding:


On 22nd May, this rainstorm reached southern Norway, where of course the snow melt season is underway.  Rain on thawing snow is a combination that is effective in initiating landslides; unsurprisingly landslides, debris flows and failures in fill slopes all occurred.  Perhaps most interesting is this video of a slump in the affected area:
I have now removed this video as it starts automatically. It can be viewed here.

This video beautifully captures a key element of the process of this type of landslide, just before the runaway failure.  This is the rapid change of state of the soil from an intact mass into a very weak, highly mobile flowing material.  Note that this is a material change – the rapid acceleration is not caused by an increase in slope gradient or suchlike.  It would be interesting to know more about the materials involved, but a possible explanation is the static liquefaction process that was also responsible for the landslides in Brazil in early 2011.  It is unsurprising that these slides cause loss of life – something that looks quite unimpressive almost instantaneously becomes a very rapid slide, with huge damage potential.

This video, which I cannot embed, also captures a reporter’s experience of getting rather too close to the landslides and floods as they occurred.  Around the one minute mark some dramatic footage of a debris flow and then a slope collapse event, is included.