7 January 2012

An update on recent landslides

Posted by Dave Petley

I am slowly catching up on the backlog after the festive break, so here is a round-up of interesting landslides that have occurred over the last fortnight or so.

1. The Pantukan landslide in the Philippines

It now appears that the losses associated with this event may not be as great as initially feared.  According to the latest NDRRMC report, 25 people have been killed and a further five are known to be missing.  However, this total is not quite in agreement with more recent media reports,  which suggest 27 fatalities to date.  This should be clearer as the day wears on.  Interestingly, several reports indicate that there was a gap between the most intense rainfall and the occurrence of the landslide.  For example:

“Renato Solidum, head of the Philippine Institute of Volcanology and Seismology (Phivolcs), said the area struck by the landslide had been battered by “bulldozing and other activities.”…The landslide struck on a clear day which was deceptive, he said. People should be taught that landslides could happen even days after the rains had stopped, he added.  “If the weather is clear, they should not assume that there’s no danger,” said Solidum in a phone interview.In the case of Pantukan, he said, “there was a lag time between rain and landslide.”

This is a very important point.  In the case of a progressive slide such as this, a time gap is to be expected, but this is indeed rarely appreciated.  Meanwhile, the authorities now plan to shut down the illegal mines and to relocate up to 20,000 people from the most hazardous areas.  Implementing such an aspiration is likely to be very difficult though.

2. Another remarkable quick clay landslide in Norway

Thanks to several people for pointing out this landslide to me.  On the first day of the year a landslide occurred at Byneset in Trøndelag near to Trondheim.  This report includes some good images of the landslide, although it does take a little time to get one’s eye into what has happened:





Although not of the best quality, this Youtube video provides a good overview of the nature of the landslide:


Although the trigger for this landslide appears to be a spell of heavy rainfall, the underlying cause is not clear.  Fortunately it caused no damage or injuries.  The way in which the debris has flowed down the valley system illustrates the extreme mobility of quick slay landslides, as the Rissa landslide video illustrates.

3. A fatal rockfall in Germany

Again, thanks to several people for pointing this one out.  On 27th December 2011 a 10-year old girl was killed on the island of Ruegen in northern Germany when a cliff collapsed onto her.  There is a gallery of images online here, which includes the rescue operations and some panaromic views of the collapse:




4. Landslide at Stromeferry in Scotland

Meanwhile, on a much smaller scale, two landslides at Stromeferry in the Scottish Highlands has blocked a major road, the A890, since 22nd December.  This is resulting in a very long diversion and quite serious disruption for this part of Wester Ross.

5. Potential landslides in Brazil

Finally, the continuation of the La Nina conditions is once again causing concern about the potential for serious landslides in Brazil, which a year ago caused such remarkably high losses Reports suggest that a landslide this week killed two people in Ouro Pretodue, and there is widespread flooding.