This blog provides a commentary on landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings. The blog is written on a personal basis by Dave Petley, who is the Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom.

This blog is a personal project that does not seek to represent Durham University.

Friday, 28 December 2007

December 2007 fatal landslide map

UPDATED! This is the monthly map for landslide fatalities for December 2007, replacing the earlier provisional map.

Fatal landslide location map for December 2007 (provisional version 1). Click for a larger map.

The statistics for the fatal landslides that I recorded are:
Number of fatal landslides: 15 (note at present I cannot work out how many individual landslides there were in the 26th-27th December Java events)
Number of fatalties: 196

Round up: 28th December

Reported fatal landslides during the last few days include:

  • Malaysia: a landslide in Kampung on 26th December killed four members of a single family
  • Colombia: a landslide on 26th Decemner in Tolima killed three people.

Indonesia Landslides

I have been trying to work out from the press reports the death toll associated with the landslides in Indonesia on 26th and 27th December. These appear to have been shallow but large failures on deforested slopes, triggered by heavy rain. The best that I have been able to come up with to date is as follows:

26th December: Karanganyar District: 61 fatalties. This appears to include a single landslide that killed about 36 people whilst they were having a meal to celebrate the clearance of an earlier landslide. This is the landslide (Picture from the Boston Globe):

26th December: A further 18 people were killed in Wonogiri District in a number of landslides.
27th December: Some reports suggest that 16 people were killed in a landslide in Eastern Java, though the picture here is sketchy.

The intensity of the rainfall is well-illustrated by the NASA TRMM data for this area (this is the 3 day accumulation as indicated on 27th December 2007):
The red and yellow areas over Java indicate high rainfall intensities.

I will update this page if I can get more information about these landslides

Thursday, 20 December 2007

New Zealand earthquake

There is news emerging this morning of a magnitude 6.8 earthquake in New Zealand today. The earthquake was situated just offshore the east coast of North Island. It is clear that the town of Gisborne has suffered some damage, though at least initially casualties appear to be light. An earthquake of this magnitude is sufficiently strong to cause landslides, and New Zealand is a landslide-prone terrain, so it will be interesting to see whether any have been triggered.

My friends at GNS in New Zealand run the excellent GEONET monitoring web site for hazards in New Zealand - surely the world leader in this area - so I recommend that site as a link for information.

Wednesday, 19 December 2007

Swiss Re loss data

The reinsurance company Swiss Re yesterday released its preliminary annual loss data for 2007.

Swiss Re Loss data

Notable elements are:
  • Their initial estimate is that >20 000 people were killed by natural and man-made catastrophes in 2007

  • Financial losses from catastrophes represented a loss of USD 61 billion across the globe

  • The three largest financial losses occurred in Europe as a result of storms
  • Four of the five biggest losses of life occurred in Asia.

  • Insured losses amounted to USD 25 billion, which is USD 9 billion higher than in 2006.

My own dataset suggests that the number of people killed by landslides in 2007 to date is about 2,600 - i.e. more than 10% of the global disaster toll.

Finally, Swiss Re usefully publish a graph of insured catastrophe losses since 1970:

Note that there appears to be something wrong with the x-axis here, but the overall upward trend is clear. 2007 probably ranks as a below trend year in terms of insured losses.

Tuesday, 18 December 2007

Construction landslide in India

The online newspaper Mangalorean today carries here some rather dramatic pictures of the aftermath of a landslide in Kavoor, India that buried and killed two labourers. An oversight of the accident is provided in this image from that site:

The report says that the accident occurred during the construction of a retaining wall using a JCB. Note in the image that deep red colour of the soils, indicating high levels of weathering. The properties of such materials are notoriously difficult to predict, meaning that failures are common. The collapse here looks to have been small, butit does not take much material to kill a person once they are buried. Such accidents are probably far more common that we realise.

Sunday, 16 December 2007

La Honda landslide

A dat off from the American Geophysical Union meeting saw my colleague Nick Rosser and I take a trip over to La Honda in the Santa Cruz mountains to take a look at the La Honda landslide. The Google Earth image (shwon on the right), though not perfect, shows the damage quite well. Not in particular the offsets on the road and upslope (on the right) the tension cracks that run across the slope. This landslide has already resulted in the destruction of about nine homes.

Our visit on Thursday occurred as works are underway, seemingly to construct some drains to reduce the pore pressures. This work seems essential as the degree of damage on the ground is now high. The image below shows the level of damage, looking down onto the road from the top of the backscarp. Note the broken road on the left - I have tried to label the key features. The displaced section is in the stand of trees in the centre of the image - maybe 15-20 m downslope.

Click on the image for an enlarged view

Installing drains seems prudent, and one can only hope that it proves to be successful. Stabilising such an active slide is undoubtedly a real challenge.

Round-up: 16th December 2007

Reported landslides during the last few days:
  • India: A landslide killed two soldiers in Ladakh on 15th December. Six people were injured. No trigger has been reported.
  • Malaysia: As is common at this time of year, Johor in southern Malaysia is suffering from prolonged heavy rainfall. A number of landslides have been reported, most notably blocking roads.
  • USA: there is an article here about an unfortunate home-owner who has had his house condemned due to a new landslide. The house is reportedly worth $1 million (£500,000). As usual, the owners insurance does not cover landslide losses. Interestingly, he reports that trees on the adjacent slopes have been removed in the last year. It would be interesting to know if this was a factor.

Vietnam landslide

There are newswire reports of a nasty landslide in central Vietnam. The reports suggest that this was a rockslide in the morning of 15th December in Tuong Duong district of central Nghe An province triggered by quarrying as part of a hydroelectric powerplant scheme. The number of workers buried is 18. Looking at the picture available here there is little chance of any survivors. The unfortunate victims appear to all have been workers on the powerplant.

Reports on 16th December suggest that the landslide had a volume of about 500,000 cubic metres, burying the victims to a depth of between 30 and 50 m. It is unsurprising then that only three bodies have been recovered to date.

Update (18th December): Thanh Nien reports that eight bodies have now been recovered, but that the rescue operations are proving to be difficult and hazardous. No clear cause of the collapse is evident but "Workers speculated Saturday that an explosion carried out on Friday might have weakened the mountain's structure and caused the landslide, but their theory has yet to be verified or disproved". Certainly poorly planned and/or executed blasting can be the cause of collapses, so it will be interesting to hear whether this is the case here.