8 June 2015
The Mount Kinabalu rockfall
The Mount Kinabalu rockfall on Friday, triggered by a shallow M=6.0 earthquake, is thought to have killed 19 people. A significant number of them appear to have been children from Singapore on a school trip to climb the mountain. They were truly in the wrong place at the wrong time, a real tragedy.
Whilst there appears to have been multiple landslides on the mountain, and indeed elsewhere, much of the loss seems to have come from the collapse of a rock pillar that formed one half of the “Donkey’s Ears” on the mountain. This is an image of this unusual rock formation before the earthquake:
And this is how they look now (via Twitter):
The column that collapsed is much larger than it might appear from the images. By coincidence, Planet Mountain ran an article late last week about new climbing routes on the Donkey’s Ears:
Interestingly, just below the climber in the image above there is a clear discontinuity inclined towards the right. About 20 m down there is another with a very similar inclination. I wonder if one of those was the detachment plane?
Whilst the image above shows that rockfalls on this column were far from uncommon (there is a huge amount of rockfall debris at the foot of the column, much of which is very large), this collapse event is very interesting. The column above would appear to be really vulnerable to the effects of seismic shaking, such that it is quite surprising that it has not collapsed previously. Does this indicate that the shaking associated with this seismic event was unusual in some way? The key is likely to be the very shallow nature of this earthquake, and its proximity to the mountain. This is the location, as given by the USGS, with Mount Kinabalu marked as well:
Such an earthquake could generate high Peak Ground Accelerations, but only over a very small area. These accelerations could have been amplified at the summit of the mountain. Thus. the key was probably the proximity of the earthquake event to the mountain and the shallow nature of the event. As such it may well prove to be an extraordinary but deeply tragic fluke.
5 June 2015
Early on Friday morning (local time) a shallow (depth = 10 km) M=6.0 earthquake struck the west coast of Sabah in Malaysia:
Whilst not being large, this earthquake appears to have been responsible for at least some landslide activity. The clearest reports at the moment at from Mount Kinabalu, which is a popular trekking/climbing route. IBT Times is reporting that at least five climbers were killed close to the summit of the mountain:
The quake caused huge boulders and rocks to roll down the mountain as the climbers were descending at about 7.17 am, the report said.
Interestingly, The Star has an image that suggests that there has been a major rockfall at the summit of the mountain that has profoundly changed the geomorphology of the peak, known as the Donkey’s ears:
This would be a very substantive rockfall. There is also some early footage from the foot of the mountain that appears to show dust plumes created by the rockfalls:
Hopefully more information will emerge in the coming hours. This earthquake should not have been responsible for large-scale loss of life, but there could be at least some infrastructure damage in a smallish area close to the epicentre.
3 June 2015
Pharkant, Burma: a liquefaction landslide in mine tailings
Pharkant is an important jade mining area in Burma. The mining is causing environmental destruction on an epic scale, and has been associated with large landslides on a number of previous occasions in recent years. The landslides appear to be primarily the result of poor mining practices, and in particular of inadequate management of the spoil generated by the mining activity.
Landslides in mine wastes are a major problem. In the UK the issue is best known because of the 1966 Aberfan landslide, in which the collapse of a spoil buried a school, with disastrous consequences. More recently, in 2013 a huge mine waste landslide in Tibet caused extensive loss of life. There are many, many other examples. One of the reasons for the terrible impact of these slides is the phenomenon known as liquefaction, in which apparently solid earth materials can transform into a very weak, fluid mass that can move both rapidly and over long distances. Under certain conditions some types of mine waste can undergo liquefaction, and very often it is the failure to manage (i.e. prevent) this process that causes catastrophic mine-related landslides.
Two videos have appeared on Youtube this week with no fanfare that illustrate this process to a degree that is unprecedented in my opinion. The videos apparently show a liquefaction landslide that occurred at Pharkant on 9th April 2015. The footage appears to have been shot from a mobile phone, and so it is understandably shaky. But I don’t think a mining-induced liquefaction landslide has ever been caught on camera like this. In terms of quality of the footage, the better video is the one that shows the second half of the landslide sequence:
The video starts as the first wave of debris spreads across the floor of the mine. Note the retrogressive nature of the landslide thereafter – material on the slope behind is going through progressive liquefaction and flowing down slope. The video is in effect capturing liquefaction in real-time.
Even better is the fact that the initial collapse event was also captured on video. Unfortunately, but understandably, the quality is much less good. In particular the video is rotated (is there a way of correcting this, does anyone know). But the footage captures the initial surge reaching the floor of the mine and sweeping up the machinery. The power and violence of the flow is terrifying:
The machines being swept up in the flow are not small by any means:
2 June 2015
Landslide tsunami video
I have absolutely no idea as to the setting or reason for this quite amazing landslide tsunami video:-
It is undoubtedly a controlled blast that has deliberately destabilised a very large section of slope. The effectiveness of the slide in generating the tsunami is clear, as is the complex nature of the water movement thereafter – see the image below. The speed and violence of this landslide tsunami is stunning.
28 May 2015
The 12th International Symposium on Landslides (12 ISL) will be held on 12-19 June 2016 at the Royal Continental Hotel in Naples, Italy. This is a symposium jointly organized by FedIGS, ISSMGE, ISRM, IGS, JTC1. The previous symposia were as follows:
- 11th in 2012 in Banff, Canada (this is the meeting at which I gave the opening keynote lecture)
- 10th in 2008 in Xi’an China;
- 9th in 2004 in Rio de Janeiro in Brasil
The organisers of the meeting have selected “Experience, Theory, Practice” as the key theme.
- Weather-induced landslides
- Earthquake-induced landslides
- Volcanic activity and landslides
- Man-induced (I assume that this means human-induced!) landslides
The Scientific Committee is encouraging authors to submit abstracts dealing with one or more of the following topics:
- Soil and rock properties
- Investigation and slope monitoring
- Mechanisms and mechanical aspects
- Analysis and modeling
- Risk analysis, assessment and management
- Control works
My view is that the International Symposium on Landslides remains the most important landslide meeting in the calendar. I have attended the last two, both of which have been both scientifically fascinating and hugely enjoyable. I strongly recommend it!
27 May 2015
Wind River Canyon in Wyoming
Unusually heavy rainfall in Wyoming on Sunday triggered a series of landslides that has led to the closure, probably until Wednesday, of the US20 highway between Thermopolis and Shoshoni as well as the BNSF railway line.
The best coverage of the event is on the County 10 website, which has a splendid gallery of images of the landslides. This image for example is both beautiful and technically interesting:
These are not simple landslides by any means. In all three cases they involves water that has been channelised on the steep slopes, from where it has collected debris, and which has triggered the detachment of boulders from the bluffs. The flows have transitioned into true debris flows on the fan below the bluffs. Note that in most cases the flows have eroded sediment from the fan in the steeper portion, adding to their volume. At the point at which the gradient of the slope reduces, just above the railway line, the flows have stopped eroding and have started to deposit, with the larger boulders being left higher on the slope and finer material further down. This is classic debris flow behaviour.
Other failures show slightly different behaviour. This one for example appears to have been erosive all the way to the river, probably because these was no reduction in slope gradient all the way down to the floor of Wind River Canyon:-
Google Earth gives a better understanding of the nature of these landslides. In fact above the bluffs each of these gulleys has quite a large catchment of more erodible material:
These upper catchments are likely to be the source of much of the sediment that forms the debris fans at the slope toe and that comprises the solid part of the debris flows.
26 May 2015
Kali Gandaki: an interesting landslide dam and breach
Early on Sunday a landslide occurred at Ranche in Myagdi District of Nepal, blocking the large Kali Gandaki river. The area affected by the landslide was affected by the earthquake of exactly a month ago, but interestingly there appears to have been no trigger. In this case the response of the authorities appears to have been exemplary, with downstream settlements, most notably the town of Beni, being evacuated and an assessment team being flown by helicopter to the site. The dam breached about 15 hours later, releasing a significant flood that caused damage but no loss of life.
The best source of information throughout was the twitter account of @gocoolchhetri, even though it is in Nepali (and Google translate does not do a good job on Nepali to English). But from the start he tweeted a series of photographs of the blockage on the Kali Gandaki, including this one of the landslide dam itself:
Note the large amounts of dust from ongoing landslide activity. This one showed the lake as it filled:
This one showed the top pf the landslide dam as the water level rose. Note the fine grained material mantling the top of the blockage:
And the dam from above:
And then the overtopping initiating:
And then developing rapidly:
Ekantipur has an article today on the aftermath of the landslide, which states that:
A 2km long and 100 metre deep lake was formed after the landslide dammed the river. The site is about 9km north of Beni, the district headquarters of Myagdi. Massive rocks started falling past Saturday midnight, damaging 27 houses in Bhagawati and Ramche VDCs. Bhimsen KC, a local of the landslide-buried Baisari, said the dam is about 40 metres high from the riverbed. He believes there is no possibility of an outburst of the lake as the dam is about 100 metres wide.
And it includes this image of the aftermath of the landslide that blocked the Kali Gandaki:
This interesting event serves once again to highlight the challenges that face Nepal in the months ahead.
21 May 2015
A landslide in Guiyang, China
A landslide yesterday morning in the Yunyan District of Guiyang, the capital city of Guizhou demolished completely an apartment building that was home to 114 people. Of these people, eight bodies have been recovered whilst eight remain missing. The authorities report that their mobile phone signals have been traced to the rubble.
It is clear that the building collapse at Guiyang was triggered by a landslide, caused by heavy rainfall. Some of the images show the collapsed block with the landslide behind. Both of these images are from Xinhua:
Judging by the images it appears that the building was connected to another, which fortunately did not collapse.
Such events are rare, but not unknown. The two best known examples are:
- The 1972 Po Shan Road landslide in Hong Kong, which killed 67 people. I featured the animation of this landslide in a previous post.
- The 1993 Highland Towers landslide in Taman Hillview, Kuala Lumpur, which killed 48 people
20 May 2015
Timing the landslide season in Nepal
In a previous post I highlighted the threat posed by landslides in the SW monsoon in Nepal. A key question now is the timing – i.e. when will the rainy season (i.e. the landslide season) start? The IMD has a tracking map for the advance of the monsoon – at the time of writing the monsoon front is lying to the SW of India in the Andaman Sea, and the advance looks to be about normal for the time of year:
Based upon the timings on this map the rains might be expected to reach the eastern part of Nepal on about 5th June, and to have covered the entire county by about 20th June. These are average figures of course, so there may be considerable variability. But of course the arrival of the monsoon front is not necessarily the start of the landslide season. Landslides can be triggered by pre-monsoon rainfall (especially convective events), and the heavy monsoon rainfall may not be associated with the arrival of the monsoon front. So I have been looking at my Nepal landslide database. In the graph below I have plotted by year for the period from 2004 to 2014 inclusive the cumulative number of fatal landslides in Nepal:-
Today (20th May) is day number 140, so it is clear that the main landslide season has yet to start. In most years the number of fatal landslides starts to increase at around about day 160 (about 8th June), with the main focus starting from about day 180 (28th June). So the main threat will start in about three weeks from now, and will intensify towards the end of next month. The landslide season typically ends at about day 280, i.e. somewhere around early October. Note that there is a great deal of variation between years both in terms of timing and the number of events.
I have highlighted two curves – 2006 and 2009. These were both years that represented the start of El Nino events – a medium-sized event in 2009-10 and a weak event in 2006-7. Interestingly both years saw a later than average start to the landslide season. We are currently in weak El Nino conditions. I am unsure as to whether this is significant.
19 May 2015
Salgar, Antioquia, Colombia
Early yesterday morning, a landslide struck the small town of Salgar in Antioquia, Colombia. Latest reports (in Spanish) are that at least 63 people were killed. At least 37 people have been injured and an unknown number are missing.
The event appears to have been a debris flow, triggered by heavy rainfall, that tore through the small town in the floor of the valley. Although the exact location of this event is not yet clear, the Salgar area is characterised by villages lying in the floor of valleys in quite steep upland areas:
Images from the scene – there is a good gallery on the El Tiempo website – suggest that the flow may have been rapid and catastrophic:-