29 August 2015

A large rockfall on the Tour Ronde, Mont Blanc

Tour Ronde, Mont Blanc

The Tour Ronde is a massif the Mont Blanc region of the Alps, on the border between France and Italy.  On Thursday the southeast face of this mountain suffered a significant landslide.  Planet Mountain has a nice piece providing an account of the landslide:

Gianluca Marra, a Mountain Guide from Courmayeur … told planetmountain.com that “a first rockfall took place at around 8:30, a second one just over an hour later” adding that “the rockfall occurred on a section of the SE Face, on the spur a bit to the right of the Normal Route up Tour Ronde.”

Luckily, no-one was killed or injured in the Tour Ronde rockfall, but it was captured on video by Gianluca Marra, and it is now on Youtube.  Two rockfalls occurred, about an hour apart.  This is the second event:

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The capture of both the rockfall component of this landslide (including the detachment of a series of large boulders) and the runout component (and in particular the slow bulldozing effect at the end of the movement phase, as was also observed in the Mount Dixon landslide in New Zealand) is particularly helpful.  Once again the way in which the rockfall component resembles a fluid flow is notable.  This is particularly evident in this remarkable photograph of the first collapse, also from Planet Mountain:

Tour Ronde

Gianluca Marra via Planet Mountain

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Finally, Planet Mountain also has a high resolution photograph of the aftermath of the Tour Ronde rockfalls after the second collapse, also taken by Gianluca Marra:

Tour Ronde

Gianluca Marra via Planet Mountain

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26 August 2015

Artvin, Turkey: an excellent video of a landslide in action

Artvin landslide

Artvin landslide via the Haber 3 website

Artvin, Turkey landslides

Heavy rainfall in Artvin, Turkey has led to extensive flooding and landslides in the last few days.  Today’s Zaman reports that eight people were killed and a further two are missing.  Landslides originating on the steep hills around the town seem to have been responsible for much of the loss.  There is a nice gallery of images on the Haber 3 website, from which the above image is taken.

There is a very interesting video on Youtube of the event:-

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Not much information is provided, and this is definitely a video that is worth viewing to the end as not much seems to be happening early on!.  I would note that this a landslide that in many ways is similar to the famous Lantau debris flows in Hong Kong, apparently starting as a smaller slip in weathered soil, and then transitioning into a highly mobile, highly destructive debris flow:

Given the number of people that were in the vicinity of the foot of the landslide, it is fortunate that the above landslide in particular landslide in Artvin was not a mass fatality disaster.

This video, also taken in the same rainfall event, is less dramatic but also quite interesting.  Again, watch to the end – those are very large boulders.

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24 August 2015

My new paper: human losses from landslides in Latin America and the Caribbean

Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean

Together with my colleague and friend Sergio Sepulveda from the University of Chile, I have just had a paper (Sepulveda and Petley 2015) published in the journal Natural Hazards and Earth System Sciences on human losses from landslides in the Caribbean and Latin America.  The paper is open access, so it is free to download.

The paper re-examines a component of the dataset that I analysed in my global landslide losses paper (Petley 2012) a few years ago.  However, in this case we have improved the dataset by enhancing the landslide search algorithm to include local information, and we have extended the time period to the ten year spell from January 2004 to December 2013.  This means that we now have a much better picture of human landslide losses in this region.

I don’t want to rewrite the paper here, so I’ll provide the headlines and give a little more detail on an interesting aspect.  Over the ten year period we have recorded a total of 11,631 deaths from landslides in 611 landslide events.  Those locations with the highest losses are parts of the Caribbean (Haiti is especially significant), parts of Central America, Colombia, and SE Brazil, as the map below, taken from the paper, shows.  Each black dot is a single landslide; the underlying base map shows the height of the terrain.

 

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We have looked at the factors that explain this distribution.  We have found that the best algorithm is a simple combination of terrain gradient (i.e. slope), mean annual rainfall and population density:

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This simple algorithm actually does a remarkable job of explaining (and predicting) the fatality-inducing landslide distribution. I think this might open the opportunity to explore future patterns of loss, if we know how population will change and we can model future rainfall patterns.  This would be an interesting follow-on study, and would make a great PhD project if anyone is interested.

A key caveat to this study though is that the 10 year period that we studied did not include a very large El Nino event.  In the last large one (1997-8) there were extensive landslides in this region.  We might expect to see a repeat in the next large El Nino, and the distribution may change too.  Of course it appears that such a large El Nino, possibly the largest recorded to date, is currently developing.  The next 12 months or so will be very interesting in this part of the world.

References

Petley, D.N. 2012. Global patterns of loss of life from landslides. Geology 40 (10), 927-930.  See also my blog post about this paper.

Sepúlveda, S.A. and Petley, D.N. 2015. Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean. Natural Hazards and Earth System Sciences, 15, 1821-1833, doi:10.5194/nhess-15-1821-2015. The full paper available to download as a PDF.

 

 

 

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23 August 2015

The rockfall physics of Wile E. Coyote and the Road Runner

Road Runner

Road Runner

The Physics of Road Runner

The classic Warmer Brothers cartoon featuring Wile E. Coyote and the Road Runner involved the repeated attempts by the hapless Coyote to capture a Road Runner bird, involving a range of increasingly outlandish contraptions, that without fail, backfired spectacularly.  Wile E. Coyote frequently attempted to use rockfalls in various guises as a device to ensnare the Road Runner.  I came across two notable examples on YouTube:

1. The Rolling Boulder

Pushing a rolling boulder down a slope to catch the fast-moving Road Runner is a challenge of timing:

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Wile E. Coyote clearly underestimated the long runout effect of some large landslides, such as rock avalanches.  Mind you, the friction coefficient of this boulder would be a challenge for even the most seasoned landslide specialist.

2. The rockfall

In this case Wile E. Coyote tries to catch the Road Runner with a classic rock topple, with a nicely placed keystone:

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Even though Wile E. Coyote has modeled the system, he demonstrated here that predicting the likely behaviour of any rockfall is difficult, especially when the blocks are irregular in shape!

I am very glad I don’t have to try to understand and forecast landslide behaviour in cartoon land!

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22 August 2015

Mount Rainier debris flows, 13th August 2015

Mount Rainier debris flows

The Mount Rainier National Park Facebook page has a nice report about a series of debris flows that occurred on the flanks of the volcano, in Washington State, USA on 13th August 2015 (and there is a good press release too).  These debris flows originated from the South Tahoma Glacier and rumbled down Tahoma Creek, as this Mount Rainier National Park map shows:

Mount Rainier

Mount Rainer National Park

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The debris flows originated as a series of collapses of ice-rich glacial sediment, triggered by the release of stored water from the glacier.  This is a common type of event on the flanks of Mount Rainier – indeed the USGS has a webpage describing them.   A helicopter overflight by Scott Beason of the Mount Rainer National Park identified the source of the flows quite beautifully:-

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Mount Rainier

Scott Beason, Mount Rainier National Park

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There is a stunning album of aerial photographs of this event on the Mount Rainier Flickr Page.

Perhaps the most exciting element of these events though was the capture of them on the local seismic monitoring network.  As the Mount Rainier National Park Facebook site observes:

“Looking at seismic data from the Pacific Northwest Seismic Network, the vibrations from the debris flow are recorded on seismograms from Rainier station RER, located at Emerald Ridge overlooking Tahoma Creek. The debris flow signal starts at ~9:50 AM PDT. Signals are emergent, pulsatory, and relatively high-frequency—all characteristics of debris flows. There was a period of time from ~9:50 AM through to ~12:45 PM where signals were occurring relatively continuously, with several tens-of-minutes-long higher-amplitude bursts at 10:15-11:10, 11:25-11:50, and 12:30-12:40 that probably correspond to major debris-flow pulses. No debris-flow-like signals showed up overnight.”

This is the seismic record:

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Liveleak has a nice video of one of the debris flow pulses passing through:

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Acknowledgement

Thanks to Lynn Highland of the USGS for bringing this one to my attention.

 

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21 August 2015

Manikaran Sahib Gurdwara: a highly unusual landslide (with a highly unusual video)

Manikaran Sahib Gurdwara

On 18th August a comparatively small but extremely high energy landslide occurred at the Manikaran Sahib Gurdwara site near to Kulu in Himachal Pradesh.  The landslide appears to have been a massive boulder roll that smashed through a part of the temple complex – I have never seen damage quite like this before (and note this is not a composite image):

Manikaran Sahib Gurdwara

Manikaran Sahib Gurdwara. PTI Photo via The New Indian Express

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Manikaran Sahib Gurdwara is a Hindu temple and site of pilgrimage, located on a set of hot springs at an elevation of about 1760 m. The presence of hot springs might indicate active faulting, perhaps suggesting that the adjacent slopes might be unusually unstable.  According to The New Indian Express:

The tragedy occurred when the landslide from Gadagi village, located at a higher altitude, came crashing down on the gurdwara, situated between the Beas and the Parvati. The landslide hit the gurdwara’s langar hall (community kitchen) and serai (accommodation) wing. “There was heavy rush of pilgrims at the gurdwara and its neighbouring areas when the landslide occurred,” said Thakur Chand, Sarpanch of the village.

The landslide killed seven people and injured a further 11.  One of the most amazing aspects of this landslide is that it was caught on CCTV footage.  This is what can only be described as an exceptionally lucky escape fot the individual in the video:

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India has a very serious problem with landslides at sites of Hindu pilgrimage, with the most obvious being the Uttarakhand disaster of two years ago.  The Google Earth image of the Manikaran Sahib Gurdwara shows that the landslide potential at this site is high.  I have indicated the location of the building on the Google Earth image below:

Manikaran Sahib Gurdwara

Manikaran Sahib Gurdwara via Google Earth

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In this case the boulder appears to have come down a small gully above the Manikaran Sahib Gurdwara, although it is not clear as to where the landslide originated.  Making sites such as Gurudwara Manikaran Sahib safe (or at least safer) is difficult and expensive.  But as these sites attract large numbers of people into locations that are landslide-prone in the monsoon season when the hazard as its its highest, action is needed.

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14 August 2015

Mangdechu in Bhutan – another significant landslide at a hydroelectric power plant site

Mangdechu in Bhutan (see also update below)

The Mangdechu hydropower project is a major hydroelectric scheme under construction in Bhutan.  A joint Bhutanese – Indian project, it involves the construction of a 56 metre high concrete dam and associated infrastructure.  Construction at Mangdechu began in June 2012 and commissioning of the plant is expected to be complete in September 2017.

Yesterday the project suffered a significant landslide, burying five workers at the site.  The Bhutanese newspaper Kuensel has been covering the story via twitter and in its online edition.  It appears that the landslide occurred when the wall of the construction pit for the dam collapsed.  Fifteen workers were in the pit at the time; whilst ten escaped, five were buried.  It is highly unlikely that they have survived, although work to recover them has been suspended because of the risk of further collapses.

The Minister for Economic Affairs in Bhutan, Norbu Wangchuk, tweeted that the Mangdechu  landslide occurred in overburden (i.e. soil and broken rock) from the top of the slope (as opposed to being a failure in the rock mass itself).   This image apparently shows the landslide debris; if correct then this does appear to be predominantly overburden.  This is not a large landslide by any means, but it doesn’t take much to kill people:-

Mangdechu

Mangdechu HEP staff via Kuensel

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Sadly this event is just the latest in a very long line of fatal landslides at construction sites for major hydroelectric projects.  Two years ago I gave a presentation at the Vajont 2013 conference in Padua that highlighted the numbers of landslides that are occurring at hydroelectric power plant construction sites, especially in the high mountains of South Asia and China.  I also wrote a paper on this topic (Petley 2013) that can be downloaded for free.  Since then there have been many more landslides that have caused loss of life at major hydroelectric power plant construction sites.  I remain concerned that this indicates that the slope hazards are being inadequately understood and managed. I fear that it is a warning of a much larger accident yet to come.

Interestingly, this week Scientific American has published an article highlighting the risks to these dam projects associated with earthquakes, questioning whether the structures could withstand a large shock.  Of course large earthquakes have the potential to cause massive landslides on the reservoir flanks that could cause waves that overtop the dam.  Given our limited ability to assess slope behaviour during large landslides, the risk should be taken seriously.

Update

The Tibet Earthquake Twitter account highlighted a BBS article from 15th July 2015 about a blockade of the Mangdechu site by truck drivers.  It includes the following quote:

Trucks, ferrying cement from Dungsam Cement Corporation and Phuentshogling, started arriving about five days ago. However, they have not been allowed to unload the cement after a landslide at the dam’s pit…MHPA’s Dam Chief, Karma Chophel said they never instructed Jaiprakash Associates to stop the work. He said the contractor stopped the work to avoid the risks from falling boulders from the landslide at the dam site.  Karma Chophel also said Jaiprakash construction is steel-netting the area to arrest the falling boulders.

Reference

Petley, D.N. 2013. Global losses from landslides associated with dams and reservoirs. In: Genevois, R. and Prestininzi, A. (eds) International Conference on Vajont – 1963-2013. Thoughts and analyses after 50 since the catastrophic landslide. Italian Journal of Engineering and Environment – Book Series N. 6, pp 63-72.

 

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13 August 2015

Shanyang landslide: a very complex slide

Shanyang landslide

Very little information has emerged in the last 24 hours about the Shanyang landslide in Shaanxi, China, which I covered yesterday.  Xinhua has a news item on it, confirming that 65 people remain missing.  There appears to have been no success in finding victims or survivors since the initial rescue effort.  The chances of finding anyone alive now must be remote.

The best new information comes in the form of a gallery of photographs from China Foto Press that are being distributed by Getty Images.  As these are commercial images I will show just one here, simply because it provides so much insight into the Shanyang landslide:

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This image appears to show the source area of the landslide in the centre background, in which an entire section of ridge seems to have collapsed.  I think that the rocks dip in the direction of initial sliding, perhaps suggesting that this is a dipslope failure?  The landslide appears to have been quite mobile, turning through 90 degrees.  Movement appears to have ceased when the landslide impacted another valley wall.

Eye witness reports suggest that the survivors ran up the valley to escape the landslide.  Those who ran down the valley were reportedly hit by the Shanyang landslide.  This would make sense if they were located near to the toe of the initial failure as movement started.

There is a notable lack of debris from buildings in the image, suggesting that the structures were completely buried.  I am unsure as to whether the crushed car in the bottom left of this image was associated with the Shenyang landslide or is left from an earlier event.

Nothing here changes my view that, although I cannot comment on this specific case, there is evidence that slopes are being inadequately managed in some mines in China.  Dipslope failures are a well-known hazard.

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12 August 2015

Shanyang County, Shaanxi: another mining-related landslide disaster in China

Shanyang County, China

In the early hours of Wednesday morning a landslide occurred at the site of the Wuzhou Mining Company in Shanyang County, Shaanxi, China.  The landslide buried three dormitories housing mine workers, burying over 60 people.  At the time of writing Xinhua reports that there are four survivors who have been recovered from the debris.

The exact location of the landslide is not clear.  Youser reports on a company called “Shaanxi Wuzhou Mining Company” as follows:-

Shaanxi Wuzhou Mining Co., Ltd. is mainly engaged in mining, processing, smelting of vanadium pentoxide, there are 5 processing and smelting production lines. Its annual production capacity is to process 800,000 t of vanadium ore; its production capacity for vanadium compounds is 5000 t/year, its production capacity for catalyst used for sulfuric acid preparation is 1000 t/year.

There are a small number if images online of the landslide, which from a geological perspective might support the idea that this is a vanadium mine.  Xinhua has this one:

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The Weather Channel has a good report too, including some additional images.  Most of these are typical for the aftermath of such disasters in China – i.e. dramatic portrayals of heroic rescuers – but one does provide some additional perspective:

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The images suggest that this was a large (some reports indicate a volume of 1.3 million cubic metres) rockslide.  The survival rate for anyone buried is likely to be very low.

This is of course the latest in a long succession of mining related landslide disasters in China – indeed they seem to be an annual event.  Previous examples include:

There are many more.  Mining landslides occur in many other countries, but China is unusual in that they regularly happen in legal (rather than illegal) mines AND cause large numbers of fatalities.  To me this indicates poor slope management.

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6 August 2015

Typhoon Soudelor – potential for landslides in China and Taiwan

Typhoon Soudelor

In the western Pacific Ocean the strongest tropical cyclone of the year to date, Typhoon Soudelor, is now forecast to make a direct hit in Central Taiwan on Friday and Saturday.  This the JTWC forecast track at the time of writing, on Google Earth:

Typhoon Soudelor

JTWC via Google Earth

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The current forecast track takes Typhoon Soudelor straight across Central Taiwan, which is both mountainous and very landslide prone:

Typhoon Soudelor

JTWC via Google Earth

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Of course there is a great deal of uncertainty about the track at present, but a direct hit on Taiwan looks likely.  Whilst the focus in terms of typhoon meteorology remains on wind, damage in typhoons is really caused primarily by water.  This is especially the case in Taiwan.  The extreme rainfall totals generated by typhoons combined with the steep mountain front in eastern Taiwan (which is both landslide prone and generates orographic intensification of rainfall) means that the landslide potential for Typhoon Soudelor is very high.    In 1996 Typhoon Herb followed a similar, but slightly more northerly, track.  When it came ashore in northern Taiwan, as a Category 4 typhoon, it generated truly epic rainfall totals – a monitoring station at Alishan in Central Taiwan recorded 1987 mm of rainfall associated with the typhoon.  Fortunately Typhoon Soudelor will be a little weaker than this when it makes landfall, but still has the potential to generate very large rainfall totals.  A great deal will depend on the rate of movement – at the moment the typhoon is forecast to pass over the island reasonably quickly, but if it stalls, as per Typhoon Morakot in 2009, then the rainfall levels have the potential to be very large.

After passing across Taiwan the typhoon will make landfall in China.  Although weakened by the interaction with land, it has the potential to generate very large rainfall totals there as well.

Landslides are inevitable as Typhoon Soudelor makes landfall.  The precipitation climatology will determine just how bad they are.  It will be well worth keeping an eye on the CWB real time rainfall observation maps on Friday, Saturday and Sunday.

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