25 July 2016
Gangotri – a very nice rockslide video from India
As Asia reels under extraordinary rainfall under strong monsoon conditions, three new, interesting landslide videos have been posted on Youtube. The first shows a rather elegant rockslide on the highway to Gangotri in Uttarakhand in northern India:
This is a classic of its type – a translational rockslide on a joint system dipping out of the slope. It is likely that trimming of the slope to create the road has removed the natural buttress at the toe of the slide, allowing slip to occur on the existing weakness when pore pressures are high.
Note also the very large amounts of dust generated by the landslide.
A spectacular landslide from China
The magnitude of the landslide is very large. Note that both section of the landslide occurred on slopes that have been cut to create the road bench, and then reinforced to provide stability:-
The aftermath of a landslide in China
And finally, CCTV has now posted a very nice video of the aftermath of the widely circulated video of a landslide destroying houses in a rural village in Hunan Province:
This is the original video:
In this case there is a railway line running across the slope – the failure appears to have occurred at the tunnel portal:
It’s hard to know whether earthworks for the line played a role in the landslide, but it seems like a prime candidate:
These three landslides all rather nicely illustrate the ways on which poor slope management is exacerbating landslide problems in upland areas of Asia.
22 July 2016
The University of Sheffield
It is with great excitement that I can announce this morning that, as from 1st November 2016, I will be moving to take up the position of Pro-Vice-Chancellor (Research and Enterprise) at the University of Sheffield. The University has formally put out a press release with this news this morning. A Pro-Vice-Chancellor is the equivalent of a Vice-President in the US system. I will help to provide strategic leadership in research across the university, and will lead on all innovation (knowledge transfer, enterprise, consultancy, business generation, etc) as well. It is a very exciting step for me.
Sheffield is a very strong, research-led Russell Group (the UK equivalent of the Ivy League) university. It’s in the World top 100 institutions, with over 27,000 students and a research income of over £140 million. It has a fabulous reputation for the quality of the student experience – it came third out of 117 institutions in the 2016 Times Higher Education Student Experience Survey for example.
Of course, this means that with great sadness I will leave the University of East Anglia on 31st October. I will do so with real sorrow – I’ve loved my time at UEA. It’s a great university, one that also focuses on the student experience (UEA came 7th in the same survey), and I have had the honour and privilege to work with some amazing people. UEA is a university that has extraordinary strength, amazing staff and an astonishing can-do attitude. Its location in the East of England means that it will play a fundamental role in the development of a gorgeous part of the UK. Until I moved to Norwich I had not appreciated what an amazing city it is. Being here has been absolutely instrumental to my career, and I have loved every minute of it. The university has a tremendous future ahead of it, and I shall watch with great interest as the university develops.
But I see amazing opportunities in Sheffield, and I cannot wait to play a part in the development of that wonderful university. It is an institution that is firmly rooted in its city and region, which will play a massive role in helping Britain to find a new path in the wake of the Brexit result. I feel deeply honoured to have been asked to join the University of Sheffield, and am hugely looking forward to working with colleagues and students across the institution.
19 July 2016
The Aranayake landslide disaster in Sri Lanka
This is a complex landslide – the image below from the report provides the best overview of the whole of the landslide, from the small failure at the crown to the debris flow at the toe:
This this image shows the complex translational component of the landslide. The report points out the unusual width of the landslide, which was not evident in most of the images at the time:
I think there are two really revealing aspects to this report. First, it provides a detailed aerial image of the very crown of the landslide:
Whilst it might on first inspection be thought that this small failure induced the overall collapse, this strange feature in the very crown of the landslide may well be a secondary failure, judging by the debris on the slope below. However, I still believe that the landslide was initiated by a failure in the crown area (but possibly over a larger area than shown above). It is interesting that the primary forest appears to have been removed in the areas on the flanks of the landslide shown in this image. This might provide an explanation for why this first failure developed.
Second, the report provides details of the settlements that were destroyed by the landslide:
An interesting question is whether this specific landslide could have been anticipated. This is the outline of the landslide superimposed onto a slope angle map:
It is probably fair to say that the specifics of this landslide could not have been identified in advance. This type of very complex, cascading failure is always going to be exceptionally hard to anticipate. However, that this type of landslide will occur in general in exceptionally heavy rainfall in the mountains of Sri Lanka can be anticipated. The houses located in the lower channel of the landslide, which is clearly identifiable in the image above, were probably at an unacceptably high level of risk from the perspective of landslide hazards.
Thanks to Kenichi Handa of JICA for highlighting this report to me, and for the most interesting discussion.
18 July 2016
In the aftermath of the May 2015 earthquake we have been worried that the first really intensive period of rainfall would lead to significant landslide problems in Nepal. Unfortunately, as Monsoon 2016 really gets into gear this scenario is playing out. Northern areas of Nepal are being affected by large amounts of rainfall. The landslides are dominating the news in Nepal – for example this is the front page of the Himalayan Times this morning:-
This is reporting the ongoing problems in the catchment of the Bhote Kosi following the landslide dam break flood of last week. Whilst the damage and disruption to this area is undoubtedly extreme, I am deeply concerned by this report of plans to bulldoze a new, 26 km long track to create an alternative alignment to Tatopani:-
The Divisional Road Office (DRO) has started work to open a 26-kilometre alternative track to connect Barhabise with Tatopani in Sindhupalchok district after a flashflood last week destroyed much of the road. The under-construction Middle Bhotekoshi Hydropower Project is providing financial assistance to open the road from Chaku to Khohra. The DRO has started construction in the remaining section of the road up to Tatopani. The project has already opened the alternative way from Chaku. The project is using three excavators at the site. Chief of the 102 megawatt project Sunil Kumar Lama said landslides continue to occur in Khohra and other areas. Senior civil engineer Sanjay Sapkota said construction works will be completed in a week though the river is still eroding sections of the Araniko Highway.
These low tech roads are both environmentally catastrophic and exceptionally hazard prone. This is an area that basically consists of quasi-stable landslide deposits, and even the existing road is very landslide-prone. In the medium term the opening of a new road is likely to make the problem far worse.
Meanwhile, other catchments are also showing distinct problems. The Mahakali River is reported to be very high and is actively eroding its banks:-
A flood in Mahakali River has started eroding the embankment at Bhimdatta Municipality-11 in Kanchan-pur district. On Sunday, the river eroded the levee that was constructed near Bhujela last year. Technicians from the People’s Embankment Programme (PEP), Kanchanpur said the flood caused by incessant rains in the hilly areas of the far-western region started eroding the banks on Saturday night. PEP chief Bhilananda Yadav said the embankment would be destroyed if the dike is swept away. “We are going to protect the embankment with gabions,” he said. Shankar Chhetri of Bhujela said they have been alerted against the river flooding their settlement.
Perhaps most worrying is the situation on the Tamor River, which has been partially blocked by a landslide. News yesterday was that the water level is rising:
Water level in landslide-dammed lake in Tamor River in Sawadin, Taplejung, has increased, leaving the downstream settlement at risk. A fresh rockfall blocked water flow in the river. Pawan Shrestha, a resident of nearby Mitlung Bazaar, told the Post over the phone that the water level in the debris-dammed lake gradually increased on Saturday.
The Kathmandu Post published an image last week of the landslide and lake from the upstream side:
17 July 2016
Glacier Bay Landslide in Alaska
Slowly more information is emerging about the very large Glacier Bay landslide in Alaska, upon which I have previously blogged. Perhaps most importantly. the landslide has now been imaged by the ESA Sentinel-2 satellite. The image was tweeted by @RemotePixel on 14th July, with the image having been collected on 11th July 2016:
It is interesting to see how little this landslide spread laterally, especially on the right side of the track (the left side is clearly constrained by the topography).
In addition, there are now a couple of videos on Youtube showing aerial images of the landslide. This one, by Jillian Rodgers of KHNS Radio, is marred by irritating music, but gives a pretty good impression of the landslide:
It includes two really good shots of the landslide source / scar area:
Paul Swanstrom, the pilot who found the landslide in the first place, has also posted a short video of the crown of the landslide:
This serves to rather beautifully show the immense fall height of this landslide. Both videos also demonstrate clearly that there is still a huge amount of rockfall activity occurring on the landslide scar, and the first video suggests that a new scree deposit is accumulating on the landslide body.
16 July 2016
Ya’an City, Sichuan: a video of a very near miss
CCTV has published on Youtube a pretty dramatic video of a very near miss for a landslide in Ya’an City in Sichuan Province, China. The accompanying text says:
Last Friday evening, when a bus with 42 passengers was driving at 318 National Road in Ya’an city, southwest China’s Sichuan Province, the 59-year-old driver noticed rocks sliding down from the mountain. He immediately pressed his brakes and reversed about 10 meters. The mountain collapsed in a minute and buried the place. But thankfully, the driver was quick enough to avert any untowardly incident.
The video is quite exciting. The consequences should the bus have been in the wrong place are clear:
Some images of the landslide appear to show a car caught up in the debris:
Fortunately this looks to have been survivable for the occupants. China Daily has more information about the landslide:
Huang Guiquan has been a driver all his life. He attributed his swift thinking to his long driving experience and familiarity with the road. “It is important for a driver to be observant of the environment all around rather than just staring at the road ahead,” he said. It was raining. He decided to stop the bus when he saw some stones falling down the mountain slope. “Trees swayed on the mountainside, but there was no wind at that moment. I thought that it must be the mountain itself that was shaking so I backed up the bus,” he said. The road is high on the Qinghai-Tibet Plateau and prone to snow in winter and landslides in summer. Huang is familiar with the road conditions on all his regular routes. “I am particularly careful when driving through the sections with sharp turns, steep slopes or frequent landslides,” he said. “It is always better to stop than rush when in danger.”
14 July 2016
Bhote Kosi, Nepal
The Bhote Kosi valley, to the north of Kathmandu, was one of the areas most seriously affected by the 2015 earthquake in Nepal. Much of the damage was caused by landslides, which occurred on many slopes. Fortunately the comparatively benign 2015 monsoon season did not exacerbate the problems as much as had been feared, but the consequences of the next period of intense rainfall always looked grim. This is a section of the valley for example:
Apart from the local population, this valley is important as it is the alignment of the Arniko Highway, which is one of only two links between Nepal and Tibet, and thus China.
The 2016 monsoon has arrived with a bang, bringing very heavy rainfall. Last week a very large flood swept down the Bhote Kosi, with devastating effects. This was almost certainly a landslide dam break flood from a blockage in the river in Tibet, and it must have been large. However, as yet the location is unclear. The Nepal media has various reports of the impact of the flood – the Himalayan Times for example reported that:
The deadly earthquake of last year had devastated Liping and Tatopani Bazaar of Sindhupalchowk. Before these places could recover, flood in the Bhote Koshi River has left these towns so battered that reconstruction seems impossible. Of the 200 houses in Tatopani and Liping bazaars, the Bhote Koshi flood has washed away 67 houses till today noon, police said.
The best image of the aftermath of the flood is on the Himalayan Times website:
It is clear that much of the damage has been caused by erosion of the toe of slopes by the flood, and subsequent slope failures. There is also a good gallery of images here. But by far the best illustration of the damage is in this Youtube video, even though it is not in English. The journalist has followed the line of the highway up to Kodari. The damage to this very important road is startling:
Sadly this may not be the end of the problems. Dinanath Bhandari of Practical Action tweeted this image of forecast 24 hour accumulated rainfall in Nepal:
This is the forecast for two days time. Whilst the heaviest rain is forecast to fall in the south, large parts of Nepal may get heavy precipitation.
10 July 2016
A small number of new landslide videos have emerged on Youtube in the last few weeks:
A debris flow in Pakistan
This very cool debris flow video was published on 17th June. No details are provided:
A road slope failure in Uttarakhand, India
This collapse event apparently happened at Nainital in Uttarakhand in India. It was posted on 5th July 2016:
A house collapse as a result of undercutting in Nagasaki, Japan
This one happened in Japan earlier this month. It appears that a retaining wall below the building has failed, undermining the foundations:
3 July 2016
Lamplugh Glacier rock avalanche: A massive new rock landslide
The media in Alaska is reporting a find by a local pilot, Paul Swanstrom of Mountain Flying Service, of a huge new landslide, the Lamplugh Glacier rock avalanche, which occurred in Alaska on Tuesday. This is yet another enormous event in this area of North America – this is an image that he took of the landslide, which is posted on his company Facebook Page:
Paul estimates that the runout of the landslide is about 6 miles (i.e. about 10 km). In a KHNS Radio article about the landslide, Colin Stark of Colombia University estimates that the volume is about 150 million tonnes, presumably based upon an initial analysis of the seismic catalogue. The landslide appears to be recorded in the Alaska Earthquake Center catalogue as a M=2.9 event on 23rd June 2016 at 08:20 local time:
The landslide appears to be a very deep-seated, ridge crest to slope toe failure of unusually large proportions:
The landslide appears to have generated a highly mobile, broad and long landslide deposit on a comparatively low angled slope, probably consistent with flow of debris over an ice bed. The landslide has developed complex structures at the toe, probably associated with the final creeping stage of movement:
This is not an area with particularly good Google Earth imagery, but I think that this is the slope that failed:
The crest of the slope appears to be at about 2030 metres elevation, and the break at the foot of the slope at about 875 m, giving a vertical extent of about 1155 metres. The toe of the deposit is at about 550 metres elevation, which means that the runout lost about 225 metres elevation over 10,000 metres, giving a travel angle of about 1.3 degrees. This is exceptionally low.
This part of Alaska is now firmly established as the global hotspot for rock avalanche activity. Recent events include the Tyndall Glacier Rock Avalanche, the Ferebee rock avalanche, the Mount La Perouse rock avalanche, the Mount Jarvis Rock avalanche and the Mount Lituya Rock Avalanche. A detailed study is urgently needed to understand why this area is so active at present.
29 June 2016
A massive secondary landslide in Devdoraki Gorge, Georgia
In 2014 I posted about a very large landslide that caused extensive damage in the Devdoraki Gorge (which is often described as the Dariali Gorge) in Georgia. That landslide left a very large volume of debris in the river bed. On 23rd June this debris mobilised into a new, secondary, landslide that caused extensive damage along the key highway that links with Georgia and Russia via the Kazbegi Customs checkpoint. Thanks to a warning system installed after the 2014 events, no-one was injured, but the damage appears to be significant. The road remains closed.
It is expected that clearing the blockage and repairing the road will take a fortnight. Exclusivenews.ge has an image that gives an impression of the magnitude of the task ahead:
The origin of these landslides is the huge pile of sediment that has been left by the retreating Devdoraki glacier. Google Earth imagery, that predates the most recent landslides, shows the magnitude of the problem:
It appears that further significant landslides are likely from this source, and thus that this river valley is likely to continue to be problematic. This valley is also the location if the Dariali Hydroelectric Power Plant (Dariali HPP) at an estimated cost of US$120 million. At the time that the Dariali HPP was being proposed there was considerable opposition on the basis of the potential for natural hazards, including sediment movement and mudflows. The impact of these multiple landslides on tghis scheme is not clear, but it appears from the top image that there is some HEP infrastructure in the river in the middle of the landslide deposit. A note (NB – this is a pdf) from an NGO, the Green Alternative, to the European Bank of Reconstruction and Development, highlights the problems:-
“There are at least three well known mudflow rivers Devdoraki, Khuro, Chkhere on the project site, that has been chosen in a way that the Dariali Hydro derivation channel portal is located exactly at the convergence of the Devdoraki and Tergi rivers and the Dariali dam, tank and headwork – just at the convergence of the Khuro and Chkhere rivers.”
The original landslide deposit is at the convergence of the Devdoraki and Tergi rivers.
The Dariali HPP is not the cause of these landslides, but is in close proximity. This most recent event is reported to have caused no damage however.