Formed in 2009, the Archive Team (not to be confused with the archive.org Archive-It Team) is a rogue archivist collective dedicated to saving copies of rapidly dying or deleted websites for the sake of history and digital heritage. The group is 100% composed of volunteers and interested parties, and has expanded into a large amount of related projects for saving online and digital history.
30 October 2017
USGS mapping of landslide density for failures triggered by Hurricane Maria in Puerto Rico
USGS mapping of landslide density for failures triggered by Hurricane Maria in Puerto Rico
The USGS has now posted online a map of the landslide density for failures triggered by Hurricane Maria in Puerto Rico in September 2017, following on from their earlier work on landslide impacts. The mapping has been undertaken using high resolution satellite images. At this stage the mapping has been undertaken on a grid square basis, with each square having an area of 4 km², with a simple three-fold classification of no landslides, fewer than 25 landslides per km², and more that 25 landslides per km². The resultant map is shown below:-
USGS mapping of landslide density in Puerto Rico as a result of Hurricane Maria
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A simple comparison with the topography of Puerto Rico suggests that, at a first order, the landscape has been a key control on the occurrence of landslides (map via Dr Jose Javier Hernandez Ayala):-
The topography of Puerto Rico. Map by Dr Jose Javier Hernandez Ayala
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The Washington Post published a map of the precipitation deposited by Hurricane Maria in Puerto Rico:
Total precipitation from Hurricane Maria in Puerto Rico, via the Washington Post
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This suggests that the landslide distribution can be primarily explained by the coincidence of intense precipitation and steep topography, which is of course unsurprising. I am sure that a more detailed analysis will be undertaken in due course. The upshot is a profoundly altered landscape. This is a Planet Labs image of the area around Lago Caonillas taken on 12th September 2017, about a week before Hurricane Maria:-
Planet Labs image of the area around Lago Caonillas in Puerto Rico, collected on 12th September 2017
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And this is the same area, after the storm, on 4th October 2017:-
Planet Labs image of the area around Lago Caonillas in Puerto Rico, collected on 4th October 2017
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References
Erin K. Bessette-Kirton, Jeffrey A. Coe, Jonathan W. Godt, Jason W. Kean, Francis K. Rengers, William H. Schulz, Rex L. Baum, Eric S. Jones, and Dennis M. Staley (2017). October 25, 2017: Map data showing concentration of landslides caused by Hurricane Maria in Puerto Rico. USGS: https://landslides.usgs.gov/research/featured/2017-maria-pr/
Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com
24 October 2017
The Tanjung Bungah landslide: a very challenging site
The Tanjung Bungah landslide: a very challenging site
In Malaysia, the fall out from the Tanjung Bungah landslide, which killed 11 construction workers in Penang on Saturday, continues unabated. The Penang State Government is reported to have stated that the cause of the landslide was human error. That may be true, but it is far from clear as to what this means. Was there a failure to understand the ground conditions properly? Or was the slope design incorrect? Or was there a failure to construct to the agreed design? Errors can occur at any stage; often there are multiple small elements. It is also important to emphasise that human error does not necessarily mean that someone was negligent (although this is sometimes the case).
Meanwhile, the pressure group Penang Hills Watch, which tries to raise awareness of the damage that is being done to the upland areas of Penang by inappropriate development, has been expressing concern about the development at the site of the Tanjung Bungah landslide for some time. Their online map of projects notes slope clearing at this location, which began is 2015, and includes a photograph of the initial slope cutting work. In June 2017 they published the image below on their Facebook site, providing a panoramic view of the location of the Tanjung Bungah landslide:-
Panoramic image of the site of the Tanjung Bungah landslide, taken in June 2017. Image from Penang Hills Watch
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With the combination of the quarry on the steep slopes behind the site, tipping upslope, and other construction in the vicinity, this looks like a very complex location in which to undertake a large development with extensive slope excavation. That is not to say that development was impossible of course, and nor that it should necessarily have been precluded. However, it does suggest that the works required a great deal of care. I continue to wonder as to the level of slope stability measures that were in place on that steep cut slope. I am sure that this will be a key focus in the investigation.
23 October 2017
Tanjung Bungah: a major construction site landslide in Malaysia that killed 11 people
Tanjung Bungah: a major construction site landslide in Malaysia that killed 11 people
A landslide at a construction site at Tanjung Bungah, which is a suburb of George Town in Penang in NW Malaysia, on Saturday killed 11 site workers. The slide, which occurred at the construction site for two 49 storey residential towers, is known to have killed workers from Indonesia, Bangladesh, Myanmar and Pakistan, as well as the site supervisor from Malaysia. The best image that I have seen of the failure is this one, via the Sun Daily:
The landslide at Tanjung Bungah in George Town, Penang. Image via Sun Daily / Sunpix by Ashraf Shamsul
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Whilst this image, from The Peninsular, gives a better impression of the scale of the landslide:-
The landslide at Tanjung Bungah in Malaysia, via The Peninsular / Reuters
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Inevitably, this significant failure is the subject of intense speculation in Malaysia, with questions being asked about the rate of development that is being undertaken in hillslope areas. I suspect that a key area of the investigation may well be the slope protection measures that were in place. It is clear that considerable slope cutting had been undertaken to create the site for the apartments. It seems surprising to me that these cuts, in apparently weathered materials, appear to have limited measures in place to ensure the stability of the slopes. Interestingly, The Star newspaper in Malaysia has some drone imagery taken if the site in July that appears to show that this section of the cut slope was facing stability issues:-
Drone imagery, taken in July 2017, showing the site of the slope failure at Tanjung Bungah landslide in Malaysia. Image via The Star newspaper.
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Malaysia has a long history of substantial landslides, some of which have been associated with major construction projects. Back in 2012 Malaysia produced a National Slope Masterplan, although sadly this is no longer available online. Interestingly, news reports suggest that the Department of Environment rejected plans for this project in 2015. A Commission of Inquiry has been established to look into this landslide.
17 October 2017
The Bellavista heap leach gold mine landslide in 2007
The Bellavista heap leach gold mine landslide in 2007
On 21st October 2007 a landslide effectively closed the Bellavista heap leach gold mine in Costa Rica. This landslide is subject to a court case that is currently being heard in the Ontario Superior Court of Justice, with a claim if about $100 million being made against SRK Consulting (US), who undertook engineering and design work, by B2Gold, based in Vancouver.
Cyanide heap leaching involves creating piles of crushed ore, mined from an open pit site in this case, which are then washed with cyanide solution. The leachate is then collected at the foot of the pile, allowing the gold to be extracted. Clearly the risks of pollution are sufficiently high that great care is needed to protect the integrity of the heap. The Bellavista site is located in heavily weathered, humid tropical mountains that are also seismically active. Slope instability is a challenge in such environments, as multiple examples on this blog have shown.
The Tierra Group has a description of the work that they undertook at the site in 2007, which includes this image of the ore heap:
The Bellavista heap leach gold mine, via the Tierra Group
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In their description of the project, the Tierra Group state that:
…our Team performed a geologic hazard assessment which ultimately identified existence of a mega-landslide (35,000,000 m3) underlying a waste rock dump and flanking a heap leach pad. A site wide Environmental Audit was prepared for the Secretaria Técnica Nacional Ambiental.
This landslide induced instability in the heap; unconfirmed reports suggest that movement was observed in 2006. The mine was reportedly closed in July 2007. In October 2007 a major landslide occurred in the southeast corner of the heap. The Ecologist has this image of the landslide, taken in January 2009:-
The aftermath of the landslide at the Bellavista heap leach gold mine. Image via The Ecologist / CEUS del Golfo via Earthworks.
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After this major landslide, the mine was closed and has subsequently been remediated. Of course I cannot comment on the liability issues that this case raises (and I cannot comment on the validity of any of the legal claims for obvious reasons), but once again problems of slope instability and mining are clear.
16 October 2017
Phu Cuong commune: a major landslide has killed 18 people in Vietnam
Phu Cuong commune: a major landslide has killed 18 people in Vietnam
Over the last few days, heavy rainfall has affected the northern and central provinces of Vietnam. The most serious incident appears to be a landslide that struck Phu Cuong commune in Tan Lac district, located in the northern province of Hoa Binh. Latest reports suggest that 18 people were killed in this event. Eleven has a good report about the impact of this major landslide:
The villagers were asleep when a massive amount of soil and rocks, triggered by heavy rainfall, rolled down an adjacent hill at about 1am Thursday, the newspaper reported. At least eighteen people, most family members, were buried alive.
One of the survivors, Bùi Văn Dũng, 26, was still shaken when recalling the disaster, 35 hours after it happened.
“We were sleeping. It was pitch-dark,” he told Dân Việt. “I opened my eyes to a loud ‘bang!’ and found myself lying under the sky, my legs buried in rocks. Everything was shaking.”
Horrified, Dũng grabbed a flashlight to find his wife and daughter in the same situation some 10 metres away. With his screams for help muted by rumbling sounds, he used the wood beams that were lying around to dig up the dirt and rocks that were crushing his wife and daughter.
The family then ran out of the area, at the sight of massive rocks rolling down from the top of the Khanh Waterfall.
The best images of this landslide can be found in this article by the IBTimes:
The site of the landslide at Phu Cuong Commune. Via IBTimes and Viet Dung/AFP
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Whilst this image shows the damage caused by the landslide:-
The site of the landslide at Phu Cuong Commune in Vietnam. Image via IBTimes and Viet Dung/AFP.
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This image, from VietNamNet Bridge, appears to show the site of the landslide:-
The site of the landslide at Phu Cuong in Vietnam. Image via VietNamNet Bridge.
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Note the enormous overhang (now disappeared) and the very obvious rockfall deposit in the foreground. A major landslide at this site should come as no surprise.
In total the heavy rainfall has left at least 72 people dead, with further rainfall forecast in the days ahead as Typhoon Khanun passes by.
9 October 2017
Lahars: an analysis of their role in losses from volcanic eruptions
Lahars: an analysis of their role in losses from volcanic eruptions
A lahar ( /ˈlɑːhɑːr/) is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley.
This video, which shows three powerful lahars (for example from Mount Unzen in 1993), is a dramatic illustration of the power and violence of these landslides:
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In a paper just published online (and open access) in the Journal of Applied Volcanology (Brown et al. 2017), Sarah Brown and colleagues from the University of Bristol have looked at the role of lahars, and other phenomena such a pyroclastic density currents, play in causing loss of life in volcanic events. This work analyses a volcanic fatality database that extends from 1500 AD to 2017, and includes 635 separate volcanic events that have resulted in almost 280,000 fatalities. In terms of landslides, they record three types of event:
- Lahars: 72 events, 49,938 fatalities
- Secondary lahars: 41 events, 6,377 fatalities
- Avalanches: 9 events, 3,525 fatalities
In this case, secondary lahars are defined as events that occur after an eruptions (sometimes years later), whilst avalanches are defined as being “inclusive of debris avalanches, sector collapse and landslides: These result from the collapse of unstable edifices due to seismicity, eruption or intense rainfall. Avalanches discharging into lakes or oceans can generate tsunamis; resultant fatalities are classified under tsunami.”
Thus, landslides of one type or another have been responsible for 59,840 fatalities, about 21.5% of the total, and roughly the same number as pyroclastic density currents.
One other aspect of this work is really interesting, which is that the research has examined how far away from the volcano the victims were located when they died, classified by the phenomenon that killed them:-
“The cumulative percentage of fatal incidents by selected eruptive hazard with distance. … Incidents are counted in 1 km bins.” Note the interesting distance profile of lahars. Diagram and caption from Brown et al. (2017)
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Lahars have a notably different distance profile from the other major volcanic hazards, with significant numbers of deaths occurring at more than 20 km from the volcano. This is a good illustration of the role that landslides can play in extending the reach of a hazardous phenomenon over a long distance, in a manner similar to the way that tsunamis extend the reach of earthquakes.
Reference
Sarah K. Brown, Susanna F. Jenkins, R. Stephen J. Sparks, Henry Odbert and Melanie R. Auker 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6, 15. https://doi.org/10.1186/s13617-017-0067-4
6 October 2017
Murchison Glacier: more information about the slowly developing rockslope failure that is affecting the hut
Murchison Glacier: more information about the ongoing rockslope failure that is affecting the hut
Earlier this week I posted about the reasoning behind the closure of Murchison Hut, the climbing and skiing refuge located above the Murchison Glacier in Aoraki/Mount Cook National Park in the South Island of New Zealand. To recap, analysis of aerial imagery and satellite images by Dr Pascal Sirguey at the University of Otago and Dr Simon Cox from GNS Science has indicated that the location of the hut has shifted 9 m laterally and 9 m vertically since November 2008, indicating that there is a large-scale rockslope failure occurring beneath the hut. Clearly there is the potential for a major failure event onto Murchison Glacier at some point (without further monitoring this is essentially impossible to predict), such that the hut has had to be closed.
Pascal has very kindly provided some additional images to illustrate the problem, and I post them here with his permission. First, this is a Pleiades high resilution satellite image draped onto a digital terrain model, that shows the location of the hut, the morphology of the slope, and the tension cracks that extend into the snow pack. The scale of the rockslope failure that is developing is clear:-
Pleaides image showing the rockslope failure developing above the Murchison Glacier in New Zealand. Image credit: University of Otago/GNS/Pleiades Glacier Observatory/PLEIADES © CNES, 2017, distribution Airbus DS.
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This image shows the tension cracks that have developed in the snow pack, and the change in location of the Murchison Hut as the rockslope undergoes creep:-
Tension cracks and the changed position of the Murchison Hut. Image credit: University of Otago/GNS/Pleiades Glacier Observatory/PLEIADES © CNES, 2017, distribution Airbus DS.
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And finally, Pascal has also produced a surface elevation difference model between 2008 and 2017:-
Surface elevation change for the rockslope above Murchison Glacier. Image credit: University of Otago/GNS/Pleiades Glacier Observatory/PLEIADES © CNES, 2017, distribution Airbus DS.
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This appears to be a site in which INSAR could very usefully provide insight into the patterns of movement, and any change in rates of creep. Anticipating what will happen next is very hard without this level of analysis; the slope could collapse today or it might still be standing in two decades.
Acknowledgement
Thanks to Pascal Sirguey at the University of Otago and Simon Cox from GNS Science for their help in putting this post together.
5 October 2017
Hurricane Maria: USGS landslide impact maps from Puerto Rico reveal the extent of the devastation
Hurricane Maria: USGS landslide impact maps from Puerto Rico reveal the extent of the devastation
From across the Atlantic, the response of the White House to the Hurricane Maria disaster in Puerto Rico looks astonishing. With little fanfare, the USGS has now started to release maps of the impacts of landslides triggered by the hurricane, created through the analysis of satellite imagery. USGS staff are past masters at this sort of mapping, which is both challenging and time-consuming. They have released the first tranche of data, for a part of northwest Puerto Rico:-
USGS map of the impacts of landslides triggered by Hurricane Maria for a part of Puerto Rico.
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It is important to note that this not a landslide map, it is a map of the impacts of landslides – i.e. the locations in which a landslide has affected a road, a building or another element of infrastructure. This is illustrated by one of the images that the USGS has released alongside the map:-
Digital Globe image of the imoacts of landslides triggered by Hurricane Maria in Puerto Rico. The red dots are the mapped impacts on humans,
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There are eight mapped impacts (the red dots) on this image, but far more landslides. Another example of the extent and impact of this event is this image, from the San Antonio Express-News, that shows multiple landslides and extremely high levels of damage in the upland areas of Puerto Rico:-
Image from the San Antonio Express-News showing landslide damage from Hurricane Maria in Puerto Rico
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The Washington Post has published a rainfall map for Hurricane Maria in Puerto Rico:-
Map of the rainfall deposited on Puerto Rico for Hurricane Maria. Map by the Washington Post
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This suggests that the mapped area had some of the higher levels of rainfall, but this amount is replicated across much of the rest of the island. In turn, this suggests that similar levels of landslide damage are likely elsewhere.
3 October 2017
Murchison Hut: an interesting landslide problem in Aoraki/Mount Cook National Park
Murchison Hut: an interesting landslide problem in Aoraki/Mount Cook National Park
The Murchison Hut is a climbers and skiers hut located on a slope above the Murchison Glacier in Aoraki/Mount Cook National Park in the South Island of New Zealand. An iconic location, it provides 10 bunks for those willing to experience the wilds of this beautiful national park:-
Murchison hut – image by Gary Dickson, Mountain Guide
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The Alpine Club New Zealand web page for this hut indicates that it is “closed due to geological instability until further notice”. The New Zealand Herald posted a piece last week explaining the background to this decision. They noted that:
“Scientists have revealed the satellite images of mountain movement that have forced the closure of a climbers’ and skiers’ hut in Aoraki/Mount Cook National Park. Murchison Hut was closed last month over fears the mountainside it sits on could suddenly collapse into the glacier about 200m below, killing anyone inside the building. The urgent decision was made by hut manager the Department of Conservation and owner the New Zealand Alpine Club on advice from experts at Otago University and GNS Science.”
The work was undertaken by Dr Pascal Sirguey at the University of Otago and Dr Simon Cox from GNS Science, who compared aerial photographs of the site collected in November 2008 with aerial imagery from November 2015 and satellite imagery from February 2017. The image below plots the location of the hut on each of those occasions:-
The location of the Murchison Hut over three epochs of imagery. Analysis by Dr Pascal Sirguey and Dr Simon Cox. Image credit: University of Otago/GNS/Pleiades Glacier Observatory/PLEIADES © CNES, 2017, distribution Airbus DS.
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The hut was found to have moved laterally towards the valley by about 9 metres and to have moved downwards, also by about 9 metres. Almost 4 metres of this movement has occurred since November 2015. This is of course consistent with the hut being located on a large, progressive landslide, estimated to have a volume of about 500,000 m³. The imagery supports this interpretation as tension cracks have been observed extending up through the seasonal snowpack, indicating that movement is ongoing.
The behaviour of such a landslide is very hard to predict, but there is the potential for an acceleration to failure. This would not be survivable for occupants of the hut, which has as a result been closed.
2 October 2017
Karnali Highway in Nepal: the danger of collecting landslide videos (viewer beware)
Karnali Highway in Nepal: the danger of collecting landslide videos (viewer beware)
The Karnali Highway is the road between Surkhet and Jumla in the Nepal Himalayas. It is a long highway – 232 km in total – through a high mountain area. Despite being a fundamentally important strategic link within the Mid-Western Development area, it is a road with many problems. Wikipedia describes it as follows:-
According to “A Value Chain Analysis of Apple from Jumla”, and the intervention strategy indicates that more than 85 percent of the Karnali highway is still unsafe as of July 2011. Many rural inhabitants along the highway have poor access to markets, healthcare facilities and schools and deal with high transport costs. Inadequate roads make it hard for farmers to transport and market their crops. There is a pressing need to provide a functional road system in the area, made more urgent by current concerns over food prices and shortages, high energy costs and social and health needs Between 60 and 75 percent of children under five are chronically malnourished, and up to 64 percent of the population live in poverty.
Google Earth image showing the route of the Karnali Highway in Nepal between Surkhet and Jumla
The road is commonly described as being the most dangerous highway in Nepal (and there are many dangerous roads in Nepal). However, it should not be forgotten that it has opened up a huge area of Nepal, improving access to education, healthcare and markets for many people. But road users are subject to substantial levels of hazard, and landslides are common, especially in the monsoon.
A video was posted to Youtube last week that illustrates this in a terrifying manner. The video is hard to watch as a man ends up being hit by a piece of flying rock. I urge discretion in viewing it.
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The location of this landslide along the road is not entirely clear – the text that accompanies it describes it as follows:-
Recently the Landslide at Dahi Kohla and now at radhauney or Kagney Khola killed a bike riders and blocked for a weeks because of massive and big stones on roads.
The Jumla Nepal blog has a report about this event as well – it describes the landslide as occurring at Bagauney, although again this location is not clear to me. It is also unclear as to whether the person who was hit by the rock was killed – I cannot find any report in the Nepal media about this event.
This is a stark illustration of the dangers of filming landslides. The rockslide rapidly transitions from a relatively small event into a very major slide, presumably because of a larger rockslope collapse upslope. The size of the blocks that are moving – fast – is notable as this still from the video shows:
Still from a Youtube video of the landslide on the Karnali Highway.
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The impact of this block into other boulders close to the road causes it to fracture, releasing pieces of fly rock. The dangers of these substantial pieces of rock are all too clear.
I often feature landslide videos on this site, and they have given us new insights into the way that slopes fail and move. However, landslides are incredibly dangerous events, and it is never worth risking your life for the sake of a piece of footage.
Dave Petley is the Pro-Vice-Chancellor (Research and Innovation) at the University of Sheffield in the United Kingdom. His blog provides a commentary on landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
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