Quarry rockfall in Guangxi

ChinaDaily is carrying the image below of an large rockfall in a former quarry in Fengshan County of Guangxi Province in China:


The accompanying report says that the landslide occurred without warning and without an obvious trigger in a long-abandoned quarry. The volume of the landslide is reported to be 21,000 cubic metres. It buried 300m of road, 16 buildings, two tractors, a car and a motorbike. Sadly, five people were killed, one person is reported missing and six people were injured, two seriously.

Images of landslides from the Wenchuan Earthquake

(In response to requests, I have edited the post to provide some comments on the images)

I am in the middle of putting together a presentation on the impact of the Wenchuan Earthquake in China in May and thus have been looking for suitable materials. I stumbled across a fantastic Powerpoint presentation with images of the aftermath of the earthquake - this can be downloaded here.

There are a number of images of the landslides triggered by the earthquake in the presentation, but I thought would highlight three of them here:

This image shows multiple shallow rock slides triggered by the earthquake. Note a few things here. First, a very large proportion (50%?) of the landscape has failed in this area. Second, the slides originate from very high on the slope - i.e. close to the ridge - and then extend all the way to the foot of the slope. This is characteristic of earthquake induced landslides and is associated with the high intensity of shaking that is experienced at the top of the slope. Finally, bite that piles of sediment at the toe of the slopes. This material will now move through the river system during periods of heavy rain and is likely to cause major problems downstream for years to come.


This picture shows a wider view of multiple shallow rock slope failures triggered by the earthquake. Most of the features pointed out above are again visible. The dust is caused by continuing landslide activity - probably in part due to aftershocks and in part with loosened material continuing to fail. The white area centre left appears to be zone of particularly shattered limestone. Note how the density of landslides reduces on the more gentle slopes in the background.

This image shows the same features as above, but perhaps with the highest density of landslides. It does appear that there is a road or track at the bottom of the slope on the right. One can only imagine how difficult it will be to maintain these roads in the future.

Dave

Alesund landslide - the verdict

Back in April I posted extensively about a landslide that occurred in the town of Alesund in Norway. This slide occurred on 26th March, when a large block slipped into an apartment block, pushing it forward by up to seven metres and collapsing the lower floors. Five people were killed.



This week, the outcome of the commission of inquiry has been released. The key points are as follows:

• Blasting of the cliff during the construction of the apartment block was responsible for the failure;
• This blasting, which was intended to create the platform for the building, weakened the hillslope;

It is clear from this image that the failure occurred on a pre-existing joint that favoured instability. It is not clear how this was missed in the original site investigation.

Presumably the blasting removed the toe of the block, destabilising it. If so then this looks to be an error of the site investigation and design. Given that the report has been handed over to Ministry of Justice, I would imagine that those involved in the original work will be somewhat uncomfortable now.

Colombia landslide images

On Sunday a landslide occurred in the El Polbado neighborhood of the city of Medellin in Colombia. It is believed that 12 people were killed. ArabianBusiness.com has published the following images of the aftermath of the event:



It is clear that this happened in a fairly wealthy area of the town, unlike many landslides in S and C. America, which occur in the slums and garbage dumps. Steep slopes are so often occupied by the very poor (as they cannot afford land on the plains) and the very rich (who like the views and the cleaner air, plus maybe a sense of superiority.

Article in the New Strait Times Malaysia

Shield your eyes from the photograph though...

People pressure on land has a telling effect

Taipei workshop presentation

On 15th November I attended a workshop on land degradation and monitoring at the Department of Geography at National Taiwan University. This was to mark both the launch of a new Land Monitoring Centre and to celebrate the 80th anniversary of the founding of the university. Below is the presentation that I gave at that meeting:


Uploaded on authorSTREAM by Dr_Dave

As usual you can download the slide show by clicking on the Dr_Dave link above.

Comments welcome.

October 2008 fatal landslide map

Rather later than is ideal (for which I apologise), here are the maps for fatal landslides in October 2008.

First, the statistics:
Number of recorded fatal landslides: 22
Number of recorded fatalities: 179
The average for the period 2002-2007 inclusive was 398 fatalities, excluding the impact of the Kashmir earthquake in 2005, so 2008 is considerably below the long term average.

This is the map of the fatal landslides that I recorded (click on the map for a better view):

As the SW monsoon ceases the concentration in S. Asia is now absent, so as usual the distribution has become far less concentrated.

This is the map of all of the fatal landslides that have I recorded in 2008 up to the end of October (again click on the map for a better view):


As usual, your comments and corrections are welcome.