25 January 2008

Rock avalanche in New Zealand and Sodbury landslip in the UK

Posted by Dave Petley

In the last week or so there have been two contrasting examples of landslides that demonstrate the poor relationship between size and impact.

First, there was this rather interesting and quite large rock avalanche in Aoraki-Mount Cook National Park, New Zealand:

The 13th January 2008 Aoraki-Mt Cook landslide
Picture from: New Zealand Herald

There is a really nice set of photos in Flash form on the New Zealand Herald website here and a good video overview of the landslide here. This is quite a large slide, with a scar (source) size of about 120 metres high, 80 m wide and 30 m deep, giving a volume of about 300,000 metres cubed by my calculation (or about 1 million metres cubed by some reports). It ran out over a glaciaer for a distance of about 2 km, probably because the slopes are steep and the debris has flowed across ice. However, no-one was killed or injured as this happened in an uninhabited area. Interestringly, there was no obvious trigger to the event.

On the other hand, rail services in SW England have been seriously disrupted by this landslide:

The 24th January 2008 Chipping Sodbury landslide
Picture from: Sky News

In comparison with the Aoraki-Mount Cook this landslide is tiny – probably jest a few hundred cubic metres. However, the landslide, which occurred as a result of the prolonged heavy rain that the UK is suffering at the moment, occurred on the SW mainline of the UK rail network. Although it didn’t reach the tracks, it has damaged signal equipment. As a result, train services were cancelled for a day and will be heavily delayed and disrupted for a while. I expect that the whole of the embankment will now need to be inspected.