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.
19 June 2014
The Devdoraki Landslide
The Devdoraki landslide was a large event in the Dariali Valley in Georgia that blocked the main road between Russia and Georgia a month ago. I featured some images of the landslide at the time, but (via Jorg Hanisch), I have been provided with a new set of very high quality photographs of the landslide. These images were collected by Georgy Gotsiridze of the Consulting Center “GeoGraphic”, Tbilisi, Georgia, who has made them available for free use. They are remarkable.
This is the source zone of the Devdoraki landslide:
Note the failure appears to have started as a rock mass failure on a very steep, ice-covered slope. This then appears to have entrained a very large volume of material as it loved down the steep slope. The dynamics are complex though – on the left side of the flow as seen from the camera the slide has spilled over a rock spur to create a second slide. Down-slope this merges again with the main slide, as shown in this image:
The most dramatic aspect of this image through is the extraordinary super-elevation of the slide when it reached the foot of the steepest slope and then needed to turn 90 degrees to follow the valley. Super-elevation is the term used when the slide travels up a slope, typically because of a sharp turn. On the right side of the image this super-elevation is very clear. This indicates that the landslide was travelling very fast at this point. The super-elevation is better illustrated in this image, showing the entire upper portion of the landslide:
Interestingly, from this point onwards the character of the slide appears to have changed markedly, I assume from a rock avalanche to a rapid debris flow. This is an image of the track of the landslide in the lower reaches:
There is some evidence of super-elevation on the outside of the bend, but to nothing like the extent upslope. The flow appears to have been strongly channelized in this portion. This is supported by this image of the slide, taken from a lower angle:
Finally, this is the landslide deposit at the point that it entered the main channel and stopped:
The diversion channel, which flowed into a tunnel, is clearly evident. The landslide does not seem to have traveled far, or to have spread dramatically, once it entered the main channel. There is little evidence of super-elevation as well. This supports the hypothesis that the movement rate was notably lower than for the initial stages.
This is a very unusual and interesting landslide – I hope that it will be analyzed and written up in detail.
17 June 2014
World Cup 2014
Alongside the World Cup 2014 tournament (for which the football has been wonderful, but let’s not talk about England…), parts of Brazil has been suffering from very heavy rainfall. The city of Natal, which yesterday hosted the match between Ghana and the USA, received extremely heavy rainfall over a 50 hour period at the start of this weekend, triggering a large landslide that destroyed 25 houses, but fortunately took no lives. This article has some images of the landslide:
The best coverage of the landslide is from some drone footage that has been placed on Youtube:
Note the extremely fine-grained nature of the soils, which make them very prone to erosion. The landslide appears to have a very unusual shape, with a planform that is similar to a cross. I would suspect that the two arms are the result of washout erosion once the main slide had occurred. Note the drainage pipes under the road on each side.
There is a very nice paper describing the geology of the Natal region of Brazil on JSTOR, dating from 1913. The paper describes the coastal region as being characterised by huge banks of sand blown in on the coastal winds, forming banks up to 75 feet (22 m high). This sand has become cemented to varying degrees.
11 June 2014
Vaðlavík (Vadlavik) landslide
A large landslide occurred at Vaðlavík (Vadlavik in the anglicised version) in eastern Iceland in April, but unfortunately this has only just come to my attention. The landslide, which is featured in an Icelandic news story dated 22nd April, has a long runout that ends in a lake. It is clear that a part of the deposit is now in the water. The bay in which this occurred in uninhabited in the winter, so the timing is unclear. RUV has some images of this impressive landslide, taken by Sigurbjörn Jonsson:
The geology of eastern Iceland is generally described as Tertiary bedrock. I am no expert on Icelandic geology, but I wonder if the slide has occurred in volcanic ash (tephra) layer overlying the solid geology. This would explain the fine-grained nature of the material and the mobility of the landslide. Interestingly I cannot see any signs of a displacement wave (small-scale tsunami).
Does anyone have any more information about this landslide?
10 June 2014
Ferebee Glacier rock avalanche
The Ferebee Glacier is located in the Alaska panhandle, in the same general area as a number of other rock avalanches that I’ve described in the last two years or so (e.g. Mount La Perouse, Mount Jarvis and Mount Lituya). Pilot Drake Olson, of Fly Drake, very kindly keeps his eyes open for such events in this area, and over the weekend spotted a new rock avalanche that has descended on to the upper reaches of the Ferebee Glacier (the location is 59.610, -135.625 if you want to take a look at the site). Marten Geertsema very kindly highlighted this event to me, and Colin Stark has also done a lot of work in the last 24 hours to characterise the slide from satellite imagery.
This is an image of the landslide, taken by Drake:
The slide has broken off a near vertical rock face and then has descended a steep ramp to flow out over the glacier. Note the lack of deposition on the ramp itself, the clear flow in the deposit (and see below) and the apparent deposit on the opposite flank. Colin has suggested, and I agree with him, that this might be the remains of a dust cloud. If so I suspect that the landslide was moving quite fast, given the size of the dust deposit. To give an idea of scale, the total vertical height difference of the landslide is over 700 m and the total distance traveled in over 2,000 m. Colin has done a rough calculation of the volume, which is in the order of 130,000 cubic metres.
Brett has also supplied this nice image of the landslide source – the bluff on the left side appears to be the one that has collapsed:
And this is a shot of the lower part of the landslide deposit:
On the right side of this image is the edge of the main landslide deposit. The fine, “fingered” structure of the deposit shown above is probably the result of late stage slow sliding – a mechanism that only came to our attention from the Mount Haast / Mount Dixon rock avalanche video.
The date of the landslide is unclear. There is a good quality Landsat 8 image from 7th May 2014 on which the landslide is not present, and another from 6th June 2014 in which it is. However, we do not have a fix from between these dates. Unfortunately, it is unlikely that this landslide generated a strong enough seismic signal to be detectable, so we may never know precisely..
9 June 2014
The Litochovice landslide occurred on 7th June 2013 in the Czech Republic. Until yesterday I hadn’t heard of this landslide, even though it is both large and interesting. GIM International, who have been undertaking a project to map the landslide using UAVs, have released this oblique aerial shot of the site:
The very obvious road at the foot of the slope (and now buried for a substantial section) is the under-construction D8 motorway linking Prague with Saxony in Germany. In this section the road is passing through the Czech Central Mountains, which are known to be landslide-prone. The road appears to be traversing a slope with a cutting on the upslope side of the highway – a working hypothesis might be that it has cut through the toe of a pre-existing landslide, which then destabilised in heavy rainfall. Note the roads across the surface of the displaced mass post-date the landslide (see images below).
The work undertaken by GIM International appears to be to map the landslide in detail, and they have made this youtube video of their GIS model of the Litochovice landslide available:
There is also a really nice image of the Litochovice landslide on a discussion forum on Skyscraper City:
An interesting aspect of the landslide is the location of the head scarp close to the quarry. An area for investigation will be whether any material from the quarry has been dumped on the upper reaches of the landslide, possibly further destabilising the slope. I suspect that the investigation team will also be very interested in the stability of the section of the slope between the landslide and the flyover that crosses the river, including the section with the two small bridges. Judging by the shape of the land I would be unsurprised to find that this section also has a history of instability.
The road is not expected to open within the next year.
I’ve also come across this interesting image of the landslide, apparently taken rather soon after the slide:
It is clear that the slide removed as a remarkably intact, coherent block – note that tracks on the slide body are essentially undisturbed. This supports the notion that this is a reactivation of an existing planar slip plane.
5 June 2014
Moving Mountains in China
Nature has today published an opinion piece, also covered by the BBC, about a major programme of work in China to create new land for urban development. The paper, Li et al. (2014), raises concerns about this enormous programme of work – in the city of Yan’an in Shaanxi Province for example, over 78 square kilometers of land are being created by removing the tops of mountains and filling in the surrounding valleys. Such programmes are enormously expensive, but the hope is that the cost can be recovered from sales of the land. These projects are clear on Google Earth where the imagery is up to date. This is the outskirts of Yan’an for example as shown in an image collected in 2012:
And this is the same site earlier this year:
The enormous change is clearly evident. The scale of this programme is immense – in some cases 100 – 150 metres of mountain top is being removed, and the total land area involved is 250 square kilometres.
Mountain top removal and landslides
The article raises a host of environmental concerns about this programme in China, including air and water pollution; soil erosion, subsidence, deforestation and ecosystem damage. All of these concerns are reasonable. Of course in the context of this blog, the interesting issue is the potential for landslides. And certainly there are reasons to be concerned. There are many reasons to think that such a programme might increase the risk of instability, including changes to groundwater flows and the cutting of slopes. However, in my view the greatest risks lie in the valley in-filling, which provides the potential for very rapid and highly destructive flowslides. In many other areas in which large amounts of fill has been emplaced, landslides have been common. Whilst techniques exist to mitigate these problems, they require great care and expertise. The extraordinary record of landslides associated with mining and hydroelectric power generation in China makes me wonder if the level of skill is sufficiently high to prevent accidents in such large projects. China is a very challenging environment for landslides, given the combination of steep slopes, weak materials, high levels of seasonal rainfall and intense seismicity.
The point of the Li et al. (2014) paper is to call for more research. They state:
We call on the Chinese government to accelerate research efforts urgently. With good guidance, land creation could proceed with fewer risks and more benefits.
China’s best researchers from Beijing, Shanghai and Wuhan should join regional collaborations. And a national network, similar to the National Basic Research Programs of China, should be established to coordinate this effort, to ensure quality and avoid duplication.
Scientists from the US Geological Survey, the US Environmental Protection Agency, the International Association of Hydrogeologists and universities in Canada, the United States and Europe should also be brought in. Local construction industries could be involved and provide funds and equipment.
Local and national governments should allocate funds according to scientific importance, guided by of a pool of national experts including hydrogeologists, environmentalists, economists and government officials. Extra funding must be found for environmental and ecological risk assessment and for economic studies of land creation. An independent management organization should be established and supervised by local government to manage and share the research data.”
I concur with this statement.
Li, P., Qian, H. and Wu, J. 2014. Accelerate research on land creation. Nature, 510(7503), 29-31.
4 June 2014
Maggie the Kakapo
The Kakapo, according to Wikipedia is a “species of large, flightless, nocturnal, ground-dwelling parrot endemic to New Zealand”, which is also known at the Owl Parrot. It has a number of unique characteristics, not least the fact that it is the only flightless parrot. It is a large and attractive bird, as the image (from New Zealand Birds Online) below shows:
Whilst once being widespread across the forested areas of New Zealand, the Kakapo was poorly adapted to the changes and threats brought by human occupation, and by the predators that people brought with them. The result is that the Kakapo is critically endangered – in November 2005 there were just 86 individuals left. This has led to extensive efforts to increase the population, and by March of this year numbers had increased to 126.
This number is so small that each bird is known individually (they are all named), and all are tracked using small radio transmitters. Thus, it is with sadness that the managers of the Kakapo Recovery Project have reported that a Kakapo known as Maggie was killed on 20th May on Codfish island. The cause of her demise was a landslide triggered by a period of heavy rainfall. Her body has been recovered from the debris – of course the transmitter meant that she was comparatively easy to find – and of course the telemetry data gives the time of death:
At the time of her death Maggie the Kakapo was just 36 (when the life expectancy is over 60 years), so this is a sad loss of an important bird.
The loss of endangered species to landslides is rarely reported – the only other example I can think of was the impact of landslides triggered by the 2008 Wenchuan earthquake on the wild panda population in Sichuan Province in China.
However, in another way such losses can be important. In the last week a major find of marine fossils has been reported in Chile. Its likely that the exceptional preservation of these animals is the result of their burial by a landslide some 250 million years ago.
30 May 2014
I’ve been at Durham University for almost 14 years, having joined initially as a lecturer in September 2000. It has been a wonderful place to work, full of extraordinarily talented colleagues and students and set in a beautiful medieval city. My career has progressed in ways that I would never have believed possible – I was made a Reader at Durham University in 2004 and then promoted to an endowed Chair in 2006. Later that same year I became Deputy Head of Faculty (Research) in Social Sciences and Health. In 2011 I took over as Executive Director of the Institute of Hazard, Risk and Resilience, and then in 2012 was made Dean of Research. Finally in 2013 I was appointed to Dean of Research and Global Engagement.
So, it is with great sadness that I am today announcing that I’ll be leaving Durham University in mid-September.
The University of East Anglia
I’m very excited to reveal that I’ll be moving the University of East Anglia, which is located in Norwich, to the north of London. I’ll be taking up the role of Pro-Vice Chancellor (Research and Enterprise), which leads on the strategic development of research and enterprise activities across the institution. I think in US terms this is similar to, but not quite the same as, a Vice-President role. I’ll also be taking up a Chair in Environmental Sciences This is a wonderful opportunity – UEA is a fabulous university with excellent staff and students.
I will be maintaining my research on landslides at UEA, and am looking forward to collaborating with colleagues there. I’ll also be continuing to work with my friends, colleagues and students at Durham and beyond.
And of course I can also assure you that I’ll be continuing to write this blog when I move.