9 July 2015

Mount Kinabalu: the day the mountain shook

Mount Kinabalu

The Straits Times in Singapore has an excellent article on the events on Mountain Kinabalu in Malaysia on the day of the earthquake last month.  Focusing primarily on the party of Singapore school children that was caught in rockfalls on the mountain, the article powerfully describes the earthquake itself and the desperate attempts to get to safety afterwards:

On the Via Ferrata, about 12 to 15 pupils, with their teachers and guides, were on the rock face when boulders tumbled down from the broken peaks of Mount Kinabalu. Amal Ashley Lim, 12, was one of the students who had just started on the Via Ferrata. Linked by a rope to schoolmates El Wafeeq El Jauzy, Navdeep Singh Jaryal Raj Kumar and Sonia Jhala, they were led by teacher Madam Nur Uzaimah Fadzali. Behind them were Daanish Amran, the Singaporean guide, and a Mountain Torq trainer. “Rocks were falling. I almost fell but luckily I grabbed on to my teacher’s legs,” Amal Ashley told The New Paper. She was lucky enough not to be hurt by the falling rocks, which were half the size of car tyres. “They hit my backpack,” she said. Her teacher, Madam Uzaimah, had pulled her under a rock overhang, but went out again to find help.  Another pupil, Emyr Uzayr, was saved by teacher Mohamed Faizal Abdul Salam. Mr Faizal cut the rope that bound him and the pupils, before cutting the ropes of Emyr’s harness. He used his body to shield him and two other pupils.

Mountain Torq trainer Hillary Augustinus, 34, was on the Walk the Torq with one group of students when he saw the rocks tumbling down. “When I look up, I can see a wave of rocks falling towards us, small, big boulders, with heavy clouds of dust. The rock face is shaking, we just lean there (on the rock),” he said.He slipped down the slope for a heart-stopping moment, but was held up by his backup safety rope; and through the rocks and dust, he saw a small crack to his right.“Out of instinct, I just crawl… to the crack. All I could do was to put my life in God’s hands,” he said. “It’s helpless, very helpless, you just couldn’t do anything.”When the quake stopped, his hands were bloodied and his right knee was hit by a rock. But he knew he had to move before more rocks fell, so he undid his rope and climbed up.A number of pupils were still clinging on to the rock face, frozen in shock.“I respect them, they were very strong, they were not crying,” he said.“We try to rescue as many as we can, one after another, and send them to the summit trail.”Despite the best efforts of the teachers and trainers, they could not save everyone.

Ten of them – most of whom were from the three groups who had started on the trail – did not live to see the sunrise from Mount Kinabalu.

There is a great deal more detail in the article, which I recommend.

The earthquake triggered extensive rockfalls from Mount Kinabalu.  This image, from the Star Online, shows the fresh rockfall scars:

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This is more or less the same view of Mount Kinabalu from the before the earthquake:

 

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The earthquake appears to have triggered some shallow landslides in steep forested slopes and a very large number of rockfalls on the near vertical cliff faces of Mount Kinabalu.  Interestingly, the less steep upper faces seem to have been affected far less.  A detailed inspection suggests that there are in fact multiple comparatively small rockfall sources across the faces, each of which has triggered the release of material from the cliff face below to create a long rockfall scar.  There are so many sources that the rockfalls have effectively removed large sections of the mountain side.

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6 July 2015

Lac du Chambon landslide: accelerated movement may indicate approaching failure?

Lac du Chambon landslide

Yesterday, French newspapers reported significantly increased rates of movement of the Lac du Chambon landslide in Isere, France.  This is the landslide that has caused a diversion of one of the key mountain sections of the 2015 Tour de France race.  For example, Europe 1 (in French) reported that movement of the Lac du Chambon landslide had increased to 2 metres per day.  On Saturday the landslide early warning sirens were set off to warn of imminent collapse, but as of the time of the articles this had not occurred.  However, several thousand tonnes of rock have been released from the slope, which may well indicate precursory activity as the mass actively deforms.

Various news outlets have images of the landslide, which has deformed greatly since I write about it last. However, the best source of information is the SAGE Ingeniere twitter feed: @SAGE_INGE (in French), from which the images below are taken

This first image shows the whole deforming mass of the Lac du Chambon landslide:

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Note the large rear tension crack and the extensive rockfall activity on the lateral shear.  Meanwhile, this higher resolution image shows the deforming landslide body in more detail:

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The tension cracks running almost directly downslope are interesting – these appear to be controlled by the rock mass structure, and probably indicate very high levels of internal deformation and shearing.

Last night @SAGE_INGE tweeted:

Cf modèle établi, le phénomène de rupture amorcé hier soir s’est prolongé avec une fracturation importante du massif en mouvement

Which translated indicates that the models have established that the phenomenon of rupture began the previous evening and that significant fracturing was occurring.  This should indicate that failure could occur reasonably soon, although predicting the time of collapse in such a complex rock mass is far from trivial.

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2 July 2015

Darjeeling: 38 killed and 23 missing in landslides

Darjeeling landslides

Darjeeling is an area of northern India that is probably most famous for a type of fine tea.  Located in the Lesser Himalaya, and heavily affected by monsoon rainfall.  Landslides have long been a significant hazard in this area, although there has also been increased concern of late that poorly planned development is greatly increasing the risk.  This is so substantial that Darjeeling is unusual in having a citizens’ group dedicated to raising awareness of the problem, the wonderful Save the Hills organisation.  They have campaigned tirelessly to raise awareness of the problems associated with poor slope management.

Yesterday the potential slope problems in Darjeeling came home to roost.  Heavy rainfall overnight triggered a series of landslides across Darjeeling, damaging buildings and roads.  The Indian Express reports at least 25 landslides across the district.  The losses make grim reading:

According to officials in the state disaster management department, 22 deaths occurred in Mirik, where 13 people were also reported missing. The remaining 17 died in Kalimpong, Lava, Sukhia and Gorubathan areas, they said. Twenty persons were reported injured and 15 missing at 8 Mile and 11 Mile areas in Kalimpong, sources said, adding that extensive damage has occurred to NH-10 and NH-55.

The largest event appears to have occurred at Tingling village near to Mirik:

Darjeeling

Google Earth

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Google Earth does have a Tingling Tea Garden marked, so it is presumably one of the two adjacent villages:

Darjeeling

Google Earth

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Judging by this image from AFP, this appears to have been a highly mobile flow type landslide:

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There is a full set of photos of the landslides on the Darjeeling Chronicle Facebook site, but please be careful as some are very graphic and quite disturbing.  Unfortunately, overnight there were further landslides as the heavy rainfall continued, and there are some suggestions that the confirmed losses might now amount to 40 people.

I have no doubt that Save the Hills will provide a full account of the landslides in Darjeeling in due course.  Yesterday they published some detail about the rainfall that triggered the landslides.  They reported that at that point Kalimpong had received 226 mm of rainfall in a six hour period.  And as Praful Rao has written:

“The worst part is we have at least 3 months of rainfall ahead.”

 

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1 July 2015

An updated landslide density map from the Nepal earthquakes from the EWF project

An updated landslide density map from the Nepal earthquakes from the EWF project

The Earthquakes Without Frontiers project has published a revised landslide density map for the Nepal earthquakes,  This map includes landslides triggered by both the 25th April and the 12 May earthquakes:-

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Note the shaded areas are those obscured by cloud, so the dataset is not quite complete. The full landslide dataset is available to download from here:

ftp://topdog.dur.ac.uk/njr/nepal_eq/UPDATE_20150622/

EWF highlight the following key points:

  • Approximately 5,600 landslides have been identified to date, including new landslides triggered by the 25 April 2015 Gorkha earthquake and the 12 May 2015 Dolakha earthquakes, as well as reactivations of landslides that were present before the earthquake sequence began.
  • Major or disruptive landsliding is limited to a zone that runs east-west, approximately parallel to the transition between the Lesser and High Himalaya. This zone includes parts of the districts of Gorkha, Dhading, Nuwakot, Rasuwa, Sindhupalchok, Dolakha, Ramechhap, and Khavre.
  • Landslides triggered by the 12 May Dolakha earthquake are included in this data set for the first time. The area of landslides triggered by the Dolakha earthquake overlaps with the eastern end of the area affected by landslides in the Gorkha earthquake. In general, locations that suffered from high landslide intensities after the Dolakha earthquake also suffered from widespread landsliding in the Gorkha earthquake. These areas have suffered damaging levels of shaking in two successive large (Mw 7+) earthquakes, and must be viewed as having a very high risk of failure during the 2015 monsoon season.
  • There have been numerous reports of cracked ground in the affected areas. There is no single interpretation of cracks in slopes generated during earthquakes and how these cracks are likely to develop through the monsoon. We recommend establishing simple monitoring (distance measurements between stakes positioned across cracks), to establish if cracks are widening or if movement of the slope has ceased. Areas that exhibit continued or accelerating movement should be treated with extreme caution.

Full details are available on the EWF blog.

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30 June 2015

Araniko Highway in Nepal: landslide problems in the monsoon

The Araniko Highway in Nepal

The Araniko Highway is the main road that links Nepal with Tibet and China, heading initially eastwards from the Kathmandu Valley and then turning north into stunningly beautiful landscape:-

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This road is of crucial importance to Nepal as it carries a very large amount of goods from China.  However, even before the earthquake this was a very landslide prone section of road, and indeed it was closed for much of last summer by the Sunkoshi landslide.  But in particular the 20 km or so of road leading up to the border is to all intents and purposes dominated by landslides.

Unfortunately this area was hit very hard by the earthquakes of May and June 2015, and landslides proved to be a major problem.  The EWF blog has a map of the mapped earthquake-induced landslide density from the earthquake – the Araniko Highway is marked on the map to the northeast of Kathmandu:-

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The Araniko Highway must have been a terrible place during the earthquakes, as some of the images that have emerged indicate:

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And now as the monsoon cranks up in Nepal this road is starting to cause major concerns. After a marathon effort to try to get the road reopen and serviceable, the Chinese authorities started to release goods stored close to the border late last week. However, this remains vert problematic – the customs post has been relocated closer to Kathmandu for example.  And yesterday My Republica reported that landslide present an “existential threat” to the area around Tatopani:-

The road stretchbetweenChakutoLiping Bazaar is full of landslides and very risky to drive through…Faults had appeared on boulders, land stretches were split and a number of dry landslidesweretrigged during the aftershocks and in the aftermath. Though, these had subsided with the decreasing frequency of the aftershocks lately, continuous rainfall in the cracked area, have made it more prone to landslides.Sludge like landslideshas been flowing down theTatopani,Kodari andLiping Bazaar. The debris brought along by the landslides has accumulated along the road in many places. Mud and clayis deposited in homes and the river is floating against its course, at some places even on the road itself. The houses thatwere spared by the quake now face serious threats from the landslides.Over 3000 Larcha and Liping residents of the area were evacuated following the May 12 aftershock and were relocated in make shift tents in Kathmandu. The latest landslide fear has seriously dashed off their hope to get back home.

The Miteri Bridge that connects both the nations has been padlocked. The busy commercial town of Khasa Bazaar remains empty and closed since the past three months. Billions worth Nepali traders’ assets are in danger. 430 consignment containers are stuck on the Chinese side. Efforts of Nepali businessmen to clear the landslides and start the transportation have failed to bear fruit due to the fresh landslides, almost every day “With the commerce going down in Tatopani, Nepali traders have started facing hardships,” Arjun Sapkota, a Khasa based trader said while elaborating on the impact of quake and the most recent landslides on the business.
So what next?  It is hard to know given that the monsoon has hardly got going in Nepal as yet.  But I would expect a wave of landslides in the first period of heavy rainfall, and then further significant landslides if and when very intense rainfall events occur.  We must hope that the area is spared a true cloudburst type of rainfall event – the consequences in terms of landslides could be just as bad as the earthquake itself.  It is going to be a case of trying to get through the next four months; thereafter a very major effort is going to be needed to secure the road before the monsoon next year.

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29 June 2015

Daning River landslide: a video that is purported to show the failure event

Daning River landslide

CCTV in China has uploaded video onto Youtube that apparently shows the Daning River landslide collapse event:

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The video seems vaguely familiar so I am unsure as to whether it is actually this event.  Certainly the shape of the failure and the type of landslide looks to be correct:

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Does anyone have any further information?  The landslide is now believed to have killed two people.

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27 June 2015

Lac du Chambon – a rapidly failing landslide that has disrupted the Tour de France

Lac du Chambon

On the banks of the Lac du Chambon in the French Alps a 1 million cubic metre landslide is rapidly developing.  This landslide is making the international news because it has caused the organisers of the Tour de France to reroute perhaps the most famous section of all – the Alpine stage that ends with the lung-bursting climb to the ski resort of Alpe d’Huez.

The slope in question on the edge of the Lac du Chambon is important because the road along the edge of the lake bypasses it via a tunnel that passes through the landslide mass.  This is a Google Earth perspective view – the road is the yellow line, with the tunnel section being the part of the road that is missing:

Lac du Chambon

Google Earth

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Interestingly, there is no obvious indication of instability in this image (from 2009), but there is a large landslide scar on the left side of the mass (the tunnel portal is clearly located on the edge of the landslide scar).  The landslide itself is now heavily disrupted, as per these images from 3France:

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In recent days the movement rate of the landslide has accelerated from 5 to 15 cm per day, suggesting that the landslide might be in a tertiary creep phase.  However, as the Mount Mannen landslide in Norway last year demonstrated, predicting failure is very challenging, and the team monitoring the landslide are sensibly making no firm predictions.  Of course, it will be very challenging for the authorities if the slope does not collapse.

There is some interesting footage of the inside of the tunnel in the video embedded in this web page, which should be visible below:

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This is a still from the video, showing the level of internal deformation that is occurring within the landslide:

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This is of course a wonderful opportunity to get a better understanding of both the dynamics of a large slope failure and the way in which the displacement wave will develop and propagate.  I hope that it will be possible to collect a detailed dataset and some video of the development of the failure.

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25 June 2015

Daning River: a landslide-induced tsunami accident on a tributary of the Yangtze

Daning River landslide

A very significant landslide occurred yesterday (Wednesday) evening on the Daning River, a tributary of the Yangtze, in Wushan County, Chongqing.  Global Times has an image of the landslide site:

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The landslide triggered local tsunami waves on the river that swamped a number of fishing boats:

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Fortunately as the landslide occurred at 6:40 most of the vessels were reported to have been vacated.  Nonetheless one person is reported missing and a further four were injured.

The landslide is intriguing.  The images seem to show a low river level (possibly the river level is being drawn down in preparation for the rainy season?) and there is no mention of a rainfall trigger.  The materials forming the landslide scar seem to be fine-grained and quite homogeneous.  The fortunate element is that the landslide did not affect the houses located nearby.

The site of the landslide is only 110 km upstream of the Three Gorges Dam, such that the river level has been elevated by the impoundment of the reservoir.  This case is likely to further raise fears of the potential for significant landslides on the banks of the lake.

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22 June 2015

Landslide-induced sediment production after the Sabah earthquake in Malaysia

Landslide-induced sediment production after the Sabah earthquake in Malaysia

The Mw=6.0 5th June 2015 Sabah earthquake in Malaysia, which killed 18 people in rockfalls on Mount Kinabalu, generated landslides that have released large volumes of sediment.  The heavy tropical rainfall in Sabah means that this sediment is now starting to enter the river systems in the form of mudflows and sediment-rich flash floods.  So, for example, last week villages around the town of Ranau were struck by a series of mudflows.  In particular, Mesilau was very badly affected,  during a period of heavy rainfall last Monday. Mesilau lies on the flanks of Mount Kinabalu, but is some way from the main massif:

Sabah Earthquake

Google Earth

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The AsiaOne website has an interesting gallery of images of the landslides that occurred last week:

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Notable here is the amount of timber in the river – to me this suggests that there must have been quite extensive landslides in the forested areas on the lower slopes of the mountain.  I have not seen detailed reports or images of these landslides.  The threat that this timber provides to the water supply and to the river itself is clear.  The post-seismic landslides from the Sabah earthquake are also moving quite large volumes of sediment, including large boulders.  Typically the riverbeds will aggrade (the bed level will rise as sediment is deposited), which will greatly increase the threat of flooding and damage to infrastructure.  This slug of sediment will work its way down the river, extending the effects of the earthquake well outside the area affected by the high ground accelerations.   In effect this will extend the effects of the earthquake in time and space.

The rainy season in Sabah starts in October, so this will be the main hazardous time.  However, in the tropical environment of Sabah heavy rainfall can occur at any point in the year.

Fortunately Malaysia has an excellent slope management organisation, JKR, part of the Public Works Department.

 

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21 June 2015

Tbilisi, Georgia:- a landslide dam-break flood killed 19 people

Tbilisi flood – 14th June 2015

A week ago, on Sunday 14th June, a flash flood ripped through a part of Tbilisi, the capital city of Georgia, causing a very significant amount of damage:

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The floods are known to have killed 19 people and to have injured a further 457 people.  Three people remain missing.  The flood inundated Tbilisi Zoo, killing large numbers of animals and releasing many more:

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Earlier this week it was reported that a tiger that escaped from the zoo killed a man before being shot.  Another tiger was thought to be on the on the loose, but I am unsure as to whether it has been recaptured.  News reports also suggest that one of the penguins in the zoo made a bid for freedom.  In an effort that is somewhat reminiscent of a scene from The Great Escape it was finally recaptured 60 km downstream.

Understandably, the flood has been very controversial in Georgia.  Whilst I am not really able to comment on the factors that underlie the event, it is clear that the flood itself was caused by the collapse of a landslide dam created on the Vere River near to the village of Akhaldaba.  The Georgian Government has produced a video animation of the landslide and flood.  Unfortunately due to a hosting problem associated with upgrading the software that hosts this site, I cannot embed videos at present.  However, you can access it via the Youtube website. Although it is not in English, the sequence of events is clear, representing a classic cascading sequence of heavy rainfall, slope failure, valley-blockage, lake formation, dam collapse and catastrophic flood / debris flow.

The landslide is estimated to have had a volume of about 1 million cubic metres.  This still from the video above shows the slide:

Tbilisi landslide.

The landslide appears to be a shallow failure for the post part, possibly with a rotational component in the headscarp area.  There appears to be a lot of water on the shear surface.  Interestingly, Tbilisi also suffered devastating floods on a number of previous occasions, and the zoo has been destroyed by floods on the Vere River at least once before.  It would be interesting to know if these earlier events were also due to landslide dams on the Vere River .

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