22 July 2014
Last Tuesday a landslide at Erzurum in Turkey destroyed an almost new, and extremely expensive, ski jumping facility. The ski jumps were constructed for the 2011 Winter Universiade, at a reported cost of 20 million Euros. The lower part of the Kiremitliktepe ski jumps collapsed. Three of the jumps have been completely destroyed (image from here), whilst the two larger jumps have been severely damaged:
Pleasingly, the collapse event was in part captured on video and is buried on Youtube:
Whilst this video provides a pretty good overview of the aftermath of the landslide
There is also an excellent gallery of images of the collapse in motion here.
This is a Google Earth perspective view of the site, taken in 2012:
Compare this with the image below of the slope, taken in 2009:
It is hard to read the topography from these images given the quality of the digital elevation model, but I would make a few initial observations. First, the topographic shape of the slope appears to have been modified – in particular, there may have been some excavation of the toe to create space for the landsliding and runout zones. The main part of the failure seems to follow the excavated and modified area for the smaller jumps on the right hand side. Second, there has been considerable additional material placed on the middle part of the slope for the main jumps (on the left side), which may have added weight to the unstable mass. And third, there is a new lake at the top of the slope, presumably to provide water for the snow-making machines.
An article in a Turkish newspaper yesterday also suggests that there were major construction defects at the site:
Prosecutors have initiated a fact-finding mission and launched an investigation into last week’s collapse. The team includes four construction and geology engineers from Atatürk University in Erzurum. The mission’s initial report has revealed some fatal problems in the construction of the towers that supported the ski jumps. The expert report shows how poorly the towers were built. An expert at the site in Erzurum found that the contractor used only one meter of steel piles in the towers’ foundations, Turkish media outlets reported on Sunday. The reports said that Sarıdağlar was required to sink 50-meter-long steel piles into the ground to support the towers. Taking a deadly risk, the contractor first poured concrete into the tower foundation then sank only a one-meter-long pile in it, a critical fault. Construction experts said, according to global standards, steel piles have to be at least 25 meters deep for towers this high. Even worse, the contractor incorrectly calculated the angle of the slopes on which the ski jumps were placed.
Thus, overall this is looking like this could be a major design and construction failure, although we’ll need to see what the official report states in due course. Given the above, the likelihood of being able to reinstate the facility without complete demolition and reconstruction look slim.
21 July 2014
Maoxian County landslide
On Thursday afternoon a rockslide occurred on a road in Maoxian County in Sichuan Province of China. Unfortunately, Xinhua reports that the landslide struck nine vehicles, including seven cars, killing 11 people and seriously injuring a further 19. Amazingly, the rockslide was captured on the dashboard camera of a vehicle close to the landslide. Indeed, this vehicle was itself struck by a rock. The footage is available on youtube. A word of warning – this does not make easy viewing:
There are several things that are worth noting here. The first is the extraordinary speed with which the blocks, some of which are very large, come down the slope. I think that one intuitively knows that this is the case, but the actual velocities are still shocking. These lumps of rock are very heavy, so the destructive power is terrible. The second is the absolute terror of those people caught in the rockslide. The rates of movement of these rocks are so high that dodging them is exceptionally difficult, especially as the trajectories that they follow are unpredictable. The man who went into the gutter adopted a good strategy for these large blocks, but of course if the whole slope had collapsed he would have been killed. And the third of course is the person who was struck by the bouncing rock. This screenshot captures both the victim (circled by the video maker) and the lump of rock (above the red car):
This was a large boulder that was travelling very fast despite the bounce that it took above the road; I suspect that the victim must have been seriously injured, although he or she does appear to be walking at least when helped to safety.
Late in the video the man in the gutter also had a lucky escape when he started to move just as another boulder struck the top of the retaining wall just along from him, as this screenshot shows:
The video was taken in an area in which comparatively few boulders were falling. The situation further along the road in the main rockfall zone must have been desperate.
15 July 2014
Over the weekend I travelled up to the Lofoten Islands, north of the Arctic Circle in Norway, to see the midnight sun. We were lucky to have quite wonderful weather, which provided the perfect opportunity to enjoy this most beautiful place:
The topography of the islands is exceptionally steep and rugged, which means that landslides and rockfalls are common. This is a very impressive ancient ridgeline rockslide- note the complete loss of a section of the ridge, the long runout of the deposit and the very large boulder sizes:
On a completely different scale, small-scale failures that have transitioned into minor debris flows are also common. This is a very nice example, with just a very small initial scar but a long track:
Sheet (face-parallel) jointing in the rock masses is also very common, which creates release surfaces for rockfalls. This is an example above the main road in which rockfall barriers have had to be installed:
The rockfalls and landslides inevitably cause some disruption. At the southwest end of the chain there is a huge project ongoing to build rockfall shelters along the road:
The Lofoten islands are one of the most beautiful, interesting places I have visited. I strongly recommend them for a weekend, or for a longer stay!
10 July 2014
Xinhua reports that the rescue operation for the Shawa mudslide in Fugong County, Yunnan Province in China has now been completed, with 17 people killed and one injured. Details of the slide are sketchy, but it does appear to have been triggered by monsoon rainfall. The reports about it are somewhat contradictory, with some appearing to emphasise that the landslide was “natural”, whilst others note that it destroyed a silicon mine. Several pictures of the landslide are now available, but they really only cover the lower portions of the slide. This is probably the best overview:
Xinhua has two albums of images (here and here), but as usual they are of the “interesting views of the heroic rescuers” genre rather than much of interest. This image appears to show the landslide deposit and the very destructive nature of the landslide:
Minzhu mudslide in Yunlong County
Xinhua also reports that there was another landslide at Minxhu, a village in Yunlong County, Yunnan province. Although much less well reported, this also appears to be been a very destructive event, with the toll likely to be 14 people, consisting of six confirmed fatalities and eight people missing.
9 July 2014
Shawa village mudslide
The landslide season across Asia has got off to an unusually slow start, with the number of events being notably lower than is usually the case in July. This may well be associated with the potential development of El Nino conditions, which sometimes suppresses both the SW monsoon across South Asia and the occurrence of tropical cyclones in the North-West Pacific. However, the signs are that the true landslide season may be about to start. The enormous Typhoon Neoguri will strike Japan over the next couple of days, bringing very heavy rainfall. Some landslides are inevitable, though the high rate of movement of the storm may prevent the very large rainfall totals that these events sometimes bring.
In China, reports today suggest that a large mudslide has occurred in Shawa village, which is located in Fugong County of Yunnan province. Xinhua has a brief report, which indicates that 17 people are missing. The caveat here of course that there must be some uncertainty about that total.
I haven’t been able to find Shawa village, but this is a Google Earth image of Fugong, the county town:
This is the sort of landscape in which landslides are an inevitable and frequent process.
8 July 2014
Komansu rock avalanche
The Komansu rock avalanche is described in a new paper by Robinson et al. (2014), which has recently been published online by the journal Landslides. The landslide is located in the Alai Valley of Kyrgyzstan, in the Trans Altai range of the Pamir Mountains. The landslide deposit is ancient – the slide has been dated at 5,000 to 11,000 years BP, which is the period after the retreat of the glaciers in this region.
The Komansu rock avalanche is both very large and quite hard to see. This is a perspective view Google Earth image of the landslide – I’ve annotated the key parts of the slide, based on the interpretation in Robinson et al. (2014):
The current landslide deposit has an estimated volume of 3 – 5 cubic kilometres (although a large part of the deposit has been eroded away), and covers an area of 64 square kilometres – i.e. this is a very large landslide indeed, and we’d expect such a large landslide in very steep, high terrain to have a long run-out. Empirical relationships from similar events suggest about 10 km. However, the Komansu rock avalanche has a run-out that is much longer than this – about 26 km – which asks real questions about the dynamics of the landslide. In other words, what was special about this landslide that allowed it to go so far? An obvious explanation is that the landslide volume was much larger than the modern deposit suggests, but given that the source area only has a volume of about 4 cubic kilometres, this then poses the question as to the origin of the additional material.
Robinson et al. (2014) have compared the hummocky topography of the landslide deposit with that of other large landslides from this region. This is a Google Earth perspective view of the deposit:
Whilst on the face of it the deposit might look a little strange, it is very similar to that found in many other large rock avalanches both in this area and more widely. From this perspective, the landslide is not unusual. The one mechanism that is known to generate usually long runouts is the presence of large amounts of snow and ice – i.e. that is a so-called rock-ice avalanche. However, such landslides tend to have a distinctive final morphology; Robinson et al. (2014) suggest that the Komansu rock avalanche deposit does not match this. An alternative, but similar possibility is that the landslide ran-out over a glacier within the valley, but again the morphology does not seem to match that observed from other known examples.
Robinson et al. (2014) suggest that the unusual mobility might be explained by the presence of a large amount of ice in the initial failure, and that the landslide then entrained a large volume of material from within the valley. So, the authors propose that the initial failure was about 4 cubic kilometres of rock together with about 500 million cubic metres of ice. This very large landslide then entrained about 4 cubic kilometres of sediment in the valley, plus additional glacial ice, to generate a flow that behaved in a manner that was similar to a volcanic debris flow, allowing the very long runout distance.
A final observation in the paper is that such landslides have substantial implications for hazard assessment in high mountain areas. These giant rock avalanches with long runout distances are clearly extremely destructive. As people increasingly populate the high mountains the likelihood of a mass fatality event, especially during a very large earthquake, increases.
Robinson, T.R., Davies, T.R.H., Reznichenko, N.V. and De Pascale, G.P. (2014). The extremely long-runout Komansu rock avalanche in the Trans Alai range, Pamir Mountains, southern Kyrgyzstan. Landslides, DOI: 10.1007/s10346-014-0492-y
7 July 2014
The Oso landslide in Washington State in March remains of great interest to the wider community, not least because of the number of lives lost and the unusually destructive nature of the landslide. A series of lawsuits have now been started in relation to the landslide. The Seattle Times has continued to investigate, and yesterday released a video that they obtained through a public-disclosure request showing continued landslide activity on the slope a month after the main failure. I have tried to embed the video, but if it does not work it can be viewed here.
The video was collected by Jeff Jones, Snohomish County geologist. It shows ongoing toppling failure from the landslide scarp. Such behaviour is quite normal as the stresses in the slope rebalance – in some ways this is anomalous to aftershocks after a big earthquake. Although the video is a bit jerky, the really interesting aspect if the mobility of the debris – even with these small slips the debris easily mobilised into a flow. Bear in mind that this is in a dry state, whereas the main failure was wet, and that the volume is a tiny fraction of the main event, and it is easy to understand why the main collapse was so destructive.
3 July 2014
Vietnam flash floods
Youtube has an interesting video of a very dramatic flash flood that appears to have occurred in Phin Pon, Sin Ho District of Lai Chau province in Vietnam on 5th June:
The new highway under construction in the background must be severely threatened by this event. The man who went down to try to recover the road roller was very lucky indeed to escape the surge towards the end of the video.
Thanks to Thomas Hodgson for finding this one.
1 July 2014
Zhaotong City landslide
The onset of the rainy season is China is, as usual, being marked by an increase in landslides. A number of news agencies have been carrying this footage of a slide occurring at Tuohe village in Daguan County, Zhaotong City in Yunnan Province on Saturday afternoon:
The landslide buried four local people, three of whom died. The heavy rains have also led to the death of a panda in Sichuan Province, apparently having been caught in a landslide, and to a landslide in Yunnan Province yesterday that killed two people and left a further 13 people missing.
20 June 2014
As I have noted previously, the global landslide cycle is dominated by the effects of the South Asia summer monsoon, which brings heavy and prolonged rainfall to the world’s most landslide prone region. In 2014 the monsoon has arrived late, which has meant that the level of landsliding across Pakistan, India, Nepal and Bangladesh is currently lower than is usually the case. This image, from the IMD, shows the monsoon precipitation deficit as of 19th June:
In South Asia, the highly landslide prone regions are in SW India (Kerala for example) and of course the Himalayan region, both of which are in a state of rainfall deficit at present.
However, the monsoon front is now advancing across the region, and with it comes reports of landslides. In Nepal overnight there were two major landslide incidents:
- In Aglung VDC- 8, Nipane, in Gulmi District a landslide buried a house, leaving nine people dead and seven missing (and assuming that they were in the house the likelihood of their having survived is very low). This is the worst landslide incident in Nepal this year.
- In Khung VDC in Pyuthan district a landslide killed five people and left another injured.
This apparently occurred in Rampur, which is in Uttar Pradesh, India; the actual date of the event is not given.
Meanwhile, over in Vietnam, the rainy season is already having an impact. This video is almost surreal – do watch to the end!
I guess there was no way back for those motorbikes. The landslide appears to be a reactivation of a previous event in deeply weathered soil. Note the precursory slips at the front of the landslide before the final collapse – the people near to the camera certainly saw this happening. Note also the flow of water that preceded the main landslide body down the road – this is often reported (and misinterpreted) for large events.