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26 March 2018

NASA models landslide climatology

NASA models landslide climatology

In the last few days, NASA has released a range of new materials and data to understand global landslide occurrence.  This work, which excellent as ever, has emerged from the team led by Dalia Kirschbaum, with substantial input from Thomas Stanley and others.  The volume of material is far too great for a single post, so here I will focus here just on their work on global landslide climatology.

The NASA team have developed a new model, Landslide Hazard Assessment model for Situational Awareness (LHASA), which determines landslide susceptibility every 30 minutes.  The NASA webpage describes the model thus:

This model uses surface susceptibility (including slope, vegetation, road networks, geology, and forest cover loss) and satellite rainfall data from the Global Precipitation Measurement (GPM) mission to provide moderate to high “nowcasts.”

Associated with this work, NASA have placed online a series of animations, all of which can be downloaded (and so represent excellent teaching resources).  The animations are made on a monthly basis, and in each case they run twice – first showing merely the climatology, and second with the landslides from the NASA landslide database overlain.  So this, for example, is the animation for August, a key landslide month globally, with the landslide events overlain:-

NASA landslide climatology

An image from a NASA animation of global landslide climatology.

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Whilst this image shows the landslide climatology for Asia only, without the landslide events overlain, for the same month:-

NASA landslide climatology

The landslide climatology of Asia in August. Still from an animation by NASA.

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The animations serve to illustrate beautifully both the highly susceptible areas of the Earth’s surface, and the changing pattern through the annual cycle.  I have frequently noted the global landslide cycle, with the peak in July and August, and the incredible importance of South and East Asia in defining this pattern.  These NASA animations provide further evidence.

If we are to reduce losses from landslides then Asia needs to be a key focus.

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22 March 2018

Wairoa: a significant valley-blocking landslide in New Zealand

Wairoa: a significant valley-blocking landslide in New Zealand

A significant valley-blocking landslide has occurred on a tributary of the Wairoa River, to the west of Gisborne, in the North Island of New Zealand.  The landslide is large – Radio New Zealand reports about 80 million tonnes (presumably about 30 million m³) [see the comment at the bottom of the article – this is more likely to be about 8 million tonnes], and Google Earth indicates that it is over 1 km long.  The Mangapoike River, the specific tributary of the Wairoa Rver, is blocked.  The impounded lake is currently about 50 m deep and is rising at 60 cm per day.  There is a significant risk of a breach, but fortunately this is a sparsely populated area of New Zealand.  Reports suggest that it was triggered by a localised earthquake earlier in March 2018.

This is the site of the landslide on Google Earth.  I have placed the market at the approximate crown of the landslide.  The image was collected in early 2011:-

Wairoa River

Google Earth image of the site of the Wairoa River landslide in New Zealand.

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This image shows that this was a pre-existing landslide that has been creeping.  Lateral scarps are evident on both flanks, and the area on the left of the landslide shows clear evidence of tension cracks.  It appears that there was active erosion occurring at the toe of the slope.

This is a Planet Labs image of the landslide, collected on 12th March 2018 and used with permission:-

Wairoa landslide

Planet Labs image, collected on 12th March 2018, showing the landslide on the Mangapoike River near to Wairoa in New Zealand.

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The image clearly shows the landslide scar and the deposit at the toe that has blocked the river. The lake is also clearly evident.  Note that at present this is not large in terms of extent, but it has the potential to generate a significant flood event.  Fortunately New Zealand has very considerable experience in dealing with these types of events.

Reference

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com

 

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21 March 2018

Planet Labs image of the Mae Moh mine landslide

Planet Labs image of the Mae Moh mine landslide

On 19th March Planet Labs captured an image of the Mae Moh mine landslide in Thailand, which I featured yesterday.  Thailand is a hazy environment, which renders high quality images quite challenging, but the image is plenty good enough to appreciate the scale and impact of the landslide.  This image, captured on 13th March (a few days before the slide), shows the conditions prior to the failure:-

Mae Moh mine landslide

Satellite image of the site of the Mae Moh mine landslide. Image captured on 13th March 2018 by Planet Labs, used with permission.

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This image, captured on 19th March by Planet Labs, shows the aftermath of the landslide:-

Mae Moh mine landslide

Satellite image of the Mae Moh mine landslide. Image captured on 19th March 2018 by Planet Labs, used with permission.

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The landslide is clearly visible in the centre of the image, most notably because of the displaced benches in the vegetated spoil slope.  The landslide appears to be a large slump, with the toe of the slide blocking a substantial section of the drainage channel.  It is worth comparing this image with the gallery of images available on the banmuang.co.th website (in Thai), which includes the following photograph of the landslide:-

Mae Moh mine landslide

The Mae Moh mine landslide. Image via banmuang.co.th.

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The images appear to show recent tipping at the top of the slope – if so, it is unclear as to whether this may have been a factor in the failure.  It is worth noting that the landslide is more complex than it might appear at first glance from the satellite image.  Although the main part of the landslide is a large slump. there is also substantial deformation in the northeast section of the slope, which has caused the damage to the conveyor seen in the photo above.  This is visible in the satellite image on careful inspection.  It will be interesting to see if this large section of slope is now stable.

Reference

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com

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20 March 2018

Mae Moh mine in Lampang province: a large, ongoing waste dump landslide

Mae Moh mine in Lampang province: a large, ongoing waste dump landslide

The Thai Visa News website is reporting an extremely large, ongoing landslide at Mae Moh mine in Lampang province in Thailand. The Mae Moh mine is the reportedly the largest open cast lignite mine in Southeast Asia – the company website reports a total mining area of almost 4000 hectares and a waste dump area of about 4150 hectares.  The website also makes great play of the operator’s careful environmental stewardship and social responsibility.  This is a Google Earth image of the vast Mae Moh mine site, collected in 2017:-

Mae Moh mine

Google Earth image of the Mae Moh Mine site, collected in 2017.

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The landslide reportedly initiated on Saturday, although it is of course likely that this represents the point at which movement was observed rather than when it started.  The images on the Thai Visa New website suggest that the volume that is in motion is large, with significant displacements having already accumulated:

Mae Moh mine

Ongoing movement at the Mae Moh mine in Thailand, via Thai Visa News.

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Mae Moh mine

Deformation at the Mae Moh mine in Thailand, via Thai Visa News.

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Such a large landslide (the Bangkok Post reports that it is over 1 km long) should not occur in a waste dump, and there is a need for action to manage the slope.  The Nation reports that this is the latest in series of incidents associated with the Mae Moh mine:-

Maliwan Nakwirot, a resident living near the mine in Lampang, yesterday said a landslide in the area on Sunday was the result of misconduct by the mine operator, which had been piling excavated soil into unstable piles instead to storing it in abandoned mine pits.  It is not the first time that there have been landslides at Mae Moh mine. There have already been three major landslides at the mine since last year, as these mountains of soil are not stable and are ready to slide anytime,” Maliwan said.

The Nation also reports that the Supreme Administrative Court ordered the evacuation of 2000 residents “as a safety precaution” in 2014, but that this has not yet happened.

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16 March 2018

Forthcoming workshop:- Triggering and Propagation of Rapid Flow-like Landslides

Forthcoming workshop:- Triggering and Propagation of Rapid Flow-like Landslides

The second JTC-1 workshop will be held from 3rd to 5th December 2018 in Hong Kong.  The topic will be:

Triggering and Propagation of Rapid Flow-like Landslides

Rapid Flow-like Landslides

Second JTC1 Workshop on Triggering and Propagation of Rapid Flow-like Landslides – this example is from the aftermath of the Kashmir earth in Pakistan in 2005.  Note the highly vulnerable refugee camps in the path of potential landslides.

The workshop is being organised by JTC1, The Hong Kong Geotechnical Society, The Geotechnical Division of the Hong Kong Institution of Engineers, and The Hong Kong University of Science and Technology.  The workshop will be held at the Institute for Advanced Study (IAS) at HKUST in Clear Water Bay, Hong Kong.  Hong Kong is of course a spectacular location for this meeting, with a long history of rapid, flow-like landslides and of course a world-leading programme to manage them.

JTC1 is the Joint Technical Committee on Natural Slopes and Landslides of the Federation of International Geo-engineering Societies (FedIGS), which is the alliance of the learned societies the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), the International Society for Rock Mechanics (ISRM), and the International Association for Engineering Geology (IAEG).

The aim of the Workshop is to promote discussion on the following topics:-

  • Improved understanding in triggering, mechanisms and runout of rapid flow-like landslides, including physical testing and numerical modelling;
  • Advances in risk management and mitigation of rapid flow-like landslides;
  • Diagnosis of notable case histories of rapid flow-like landslides; And
  • Potential impact of climate change on initiation and propagation of rapid flow-like landslides.

Highlights of the workshop include:

Registration details are available here; the deadline is 2nd April 2018. Extended abstracts should be submitted by 30th June 2018.

This will undoubtedly be a very enjoyable and impressive event. I intend to attend, and hope that I will see you there.

 

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15 March 2018

Llusco, Peru: a dramatic landslide has destroyed 100 houses

Llusco, Peru: a dramatic landslide has destroyed 100 houses

A major landslide at Llusco in the Cusco region of Peru over the last few days has led to the destruction of over 100 houses, and the declaration of a state of emergency by the government.  The local authorities have stated that the landslide was caused by high pore water pressures, rather than by seismic activity. The landslide is reported to cover an area of about 30 hectares.  The best images that I have seen of the landslide reside in a Youtube video that was shot by a drone by Fameco Films and Art.  This should be visible below:-

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Based on this video the landslide appears to be a very large slump, with movement of a very large block.  However, the shear surface is, I suspect, non-circular, which has caused the block to fracture extensively.  This can be seen in the image below, taken from the video:-

Llusco landslide

Extensive fracturing in the displaced mass at Llusco in Peru. Image from a drone video posted to Youtube by Fameco Films and Art.

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The toe portion of the landslide has suffered very extensive fracturing and deformation, with a large amount of extension of the mass:-

Llusco landslide

Deformation of the frontal portion of the displaced mass at Llusco in Peru. Image from a drone video posted to Youtube by Fameco Films and Art.

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Unsurprisingly this has caused very extensive damage to the houses, which are no longer habitable.  The size of the fractures between displaced blocks is quite remarkable:

Llusco landslide

Damaged houseson the landslide at Llusco in Peru. Note the size of the fractures that have opened between the displaced blocks.Image from a drone video posted to Youtube by Fameco Films and Art.

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In many ways this landslide feels quite similar to the Seafront landslide (often known as the Cow Slide), triggered by the Kaikoura earthquake in New Zealand.

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14 March 2018

Papua New Guinea earthquake – continued landslide impacts

Papua New Guinea earthquake – continued landslide impacts

The continued scandalous response (or, more precisely, non-response) of the international community to the Papua New Guinea earthquake is highlighted in this article on the New Zealand website stuff.co.nzThe article includes this telling section:-

New Zealander Tony Stuart, Executive Director of UNICEF Australia, visited the Mt Hagen area last week and says while the locations are very different, the devastation is familiar.  “It’s like Christchurch, but without the response.”  People were walking around saying “why doesn’t the rest of the world want to come and help us?” he said.  “Because so much of it is hilly terrain, houses just disappeared. But on the flat as well, solid brick buildings were completely flattened. It’s taken everything down.”  “It’s clear that there are going to be far more fatalities”.

Meanwhile, I highlighted immediately after the earthquake that large numbers of landslides were likely, and subsequently that landslide dams pose a significant threat.  That now looks all too prescient, sadly.  On 13 March the local newspaper, the Post-Courier, reported that:-

Three villages have been completely wiped out in an avalanche of water and landslides last Wednesday.  The villages, with a population of 47, are located at Jam Valley between Hela and Western provinces. Ten people have been confirmed dead and another 17 were seriously injured.  Because of its remoteness, news of the disaster reached relief aid workers last weekend, four days after the disaster.

Hides PDL7 Special Purpose Authority chairman Andy Hamaga said that water in three mountain lakes had moved against the sides of the mountains, forcing them to collapse and emptying the lakes’ waters and mud into the unsuspecting villages. Mr Hamaga said these villages – Togayu, Oka and Sepitu – are situated within the Hides PDL 7 project area and come under the Kamia-Kera Block of the PNG LNG Project landowner group in Hela Province.

It continues to be really difficult to get decent satellite imagery of this area.  But this is a Planet Labs image of a part of Mount Sia, taken on 26th Feb at 00:13 UTC, the day after the earthquake.  The image is affected by haze and cloud, but the terrain is visible:-

Papua New Guinea earthquake

Planet Labs satellite image of a part of the Mount Sisa area after the Papua New Guinea earthquake

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This is exactly the same area from a Planet Labs image dated 7 March 2018:-

Papua New Guinea earthquake

Planet Labs image of the area affected by the Papua New Guinea earthquake. Image dated 7 March 2018.

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Sadly the area upstream that has been affected by this event is covered in cloud.  But there is no doubt that this area has been affected by a catastrophic event, most likely landslide related.

Reference

Planet Team (2017). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://api.planet.com

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12 March 2018

Cadia Gold Mine – another tailings dam failure

Cadia Gold Mine – another tailings dam failure

On Friday a tailings dam collapse occurred at the Cadia Gold Mine, operated by Newcrest Mining, in Orange, New South Wales, Australia.  Cadia is one of the largest open cur gold and copper mines in Australia.  The collapse has led to the cessation of mining operations at Cadia.

The collapse appears to have occurred on the Northern Tailings Storage Facility, on a dam that links two tailings storage areas.  In consequence there has as yet been no release of pollution from the tailings site, and there were no injuries. Newcrest have released this image of the tailings dam failure:-

Cadia mine tailing dam failure

The tailings dam failure at Cadia mine in Australia. Image from Newcrest

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They have also put out a detailed press release that notes the following:-

An area of the embankment slumped late Friday 9 March 2018 following the identification of cracks earlier in the day in the dam wall during a regular inspection. When such cracks were noticed the site team quickly engaged an independent geotechnical consultant to assist Newcrest’s geotechnical engineers at Cadia with an
inspection and preliminary assessment of the embankment.

As a precaution Newcrest stopped depositing tailings into both dams late in the day of 9 March 2018. To allow site management to focus on the evaluation of the event and remediation plans, Newcrest progressively suspended all mining and processing operations at Cadia, fully effective on 10 March 2018.

The area around the tailings dam has been secured, and a comprehensive geotechnical monitoring system has been implemented, involving radar and cameras, to allow real time assessment of ground movement of the dam wall. No further movement of the wall has been detected since Friday night.

The statement also includes an aerial image of the failure:

Cadia tailings dam failure

Aerial image of the tailings dam failure at Cadia mine. Image released by Newcrest.

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It is clear that most of the tailings behind the failed section have not collapsed, which has prevented a large-scale release of tailings into the lower pond.  There will be an urgency to try to understand this failure in order to ensure that the remainder of the tailings dam is safe, and of course to ensure that the now unrestrained tailings do not start to flow.

Interestingly, mining.com reports that the collapse occurred a few days after two seismic events in this area:

Even though the accident took place just a few days after two earthquakes of magnitude 2.7 hit the area, Newcrest did not mention any connection between these events. Back in 2017, the mine had to be shut down after it was hit by a magnitude 4.3 earthquake. It took about three months to bring it back to partial production.

It would be quite surprising if this structure was not able to withstand seismic events of this magnitude.

Whilst a major environmental disaster has not occurred at this site at the time of writing, this event once again serves to demonstrate that the failure rate for tailings dams is absolutely unacceptable. As I have said before, this frequency of failure, in combination with the potential consequences of tailings releases, would not be accepted in any other area of geotechnical engineering.

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5 March 2018

Landslide weirdness – a landslide as a “crashed UFO”

Landslide weirdness – a landslide as a “crashed UFO”

Occasionally I like to feature items of landslide weirdness, such as face of Jesus in a landslide scars or landslides being caused by poleward shifts.  Today I think I may have found one that tops them all to date – a landslide that is interpreted as being a crashed UFO.  The source is a Youtube video that appears to have gone viral.  Posted on Youtube by “Secureteam10”, the video purports to show a crashed UFO on the island of South Georgia. At the time of writing it has been viewed over 700,000 times:-

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The core of the video is this object and its associated trail through the snow:-

UFO? No, a landslide

The apparent UFO (actually a long runout landslide) in South Georgia, via Google Earth

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In the video this is interpreted as a UFO that has crash landed.  The object is seen as being a 50 metre long alien space craft that has slid to a stop across the snow and ice, having first crashed into the mountain.

However, the image above shows a different story (even if you discount the problems of the trajectory of the UFO before it struck the hillside).  The image clearly shows that the trail extends from a landslide deposit.  A closer view confirms this:-

UFO? No, a landslide

The landslide deposit, and above it the scar, for the apparent UFO, via Google Earth.

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Clearly evident is a comparatively recent (at the time of the image) landslide deposit.  The trail extends high into this deposit.  Upslope from the landslide mass are a series of scars – it is not possible to determine from which of these the landslide originated.

Of course the runout trail is quite unusual.  I am not sure if a block has detached from within the mass, and then moved downslope, or if it tumbled onto the mass from above, and then slid.  If I was a betting man (and I am not) I might go for the latter explanation, but without a more detailed investigation I am speculating.  But either way this is conventional landslide behaviour on snow and ice covered surfaces, and we have seen other large isolated boulders travel long distances. In this case the elongate shape of the block favoured sliding rather than rolling, but as the friction of the substrate is low the distance travelled can be large.

It is an interesting case study, and as such it is a good find by Secureteam10.  But it is not a UFO.

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2 March 2018

More detail on the Papua New Guinea landslide dams

More detail on the Papua New Guinea landslide dams

Information remains sketchy about the Papua New Guinea landslide dams that I have highlighted over the last few days, not least because the area remains cloud-affected, which is rendering the collation of satellite imagery difficult.  The best image that I have been able to track down is a Sentinel 2 image that was collected on 27th February 2018, and available via the EO Sentinel Viewer tool.  This image does not capture the entirety of the earthquake affected area, so we remain unsure as to what might be lurking under the cloud.  It does however capture a series of landslide dams in the epicentral area.  This is an overview image of the sites that I describe below; I believe that this area covers the Tagari River, a tributary of the Heggio River [corrected 2nd March in light of comment below]:-

 

Papua New Guinea landslide dams

Overview image of the Papua New Guinea landslide dams. The numbers indicate the locations of the sites identified below. Sentinel 2 image collected on 27th February 2018, via ESA, viewed via the EO browser.

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In terms of detail I shall work downstream.

1. The first dam that is apparent is the one shown below, located at -6.036, 142.899. This appears to be about 1 km in length (in terms of the amount of river that is blocked), and a lake has formed.  This dam appears to have breached already, so should not accumulate much more water, but may be problematic in a flood:-

 

Papua New Guinea landslide

The first of the Papua New Guinea landslide dams. Sentinel 2 image collected on 27th February 2018, via ESA, viewed via the EO browser.

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2. Immediately downstream (the distance is about 5 km) is a much larger and much more complex landslide dam, located at -6.074, 142.938.  This appears to have blocked the river over a distance of over 2 km, although the height of the debris is hard to ascertain.  On the images this looks like some sort of spread or flow type slide:-

 

Papua New Guinea landslide dams

The second of the Papua New Guinea landslide dams. Sentinel 2 image collected on 27th February 2018, via ESA, viewed via the EO browser.

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Note the very substantial lake that has already developed at this site.  That lake appears to be about 1.5 km in length at the time that the image was collected.  Downstream from this location is at least one further major slide that may have blocked the valley.

3. Further downstream the largest landslide complex appears to be the largest landslide in this area, located at -6.247, 143.066:-

 

Papua New Guinea landslide dams

The largest of the Papua New Guinea landslide dams. Sentinel 2 image collected on 27th February 2018, via ESA, viewed via the EO browser.

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Whilst much of this landslide is in cloud, it appears to be a giant rockslope failure.  It has blocked the river over a distance of at least 2 km.  I suspect that this may well be the dam that is visible in the videos by Bernard James McQueen, and now posted on Facebook.  This is probably the most worrying of all of the dams.  At present the volume of impounded water is small due to the blockages created upstream.

4. Finally, a few kilometres downstream are some other landslide dams of various scales, including this sequence, which is located at -6.327, 103.105. I suspect here the blockages are small, but nonetheless are of concern:-

The largest of the Papua New Guinea landslide dams

Sammler rockslides, part of the The largest of the Papua New Guinea landslide dams sequence. Sentinel 2 image collected on 27th February 2018, via ESA, viewed via the EO browser.

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So, overall, there are at least four landslide dams on the Heggio River, some of which appear to be large.  The level of hazard, and the vulnerability of people and other assets downstream, in unclear at present.  But, the possibility of a sequential failure of these dams cannot be ruled out.  In an area with metres of rainfall per year, these Papua New Guinea landslide dams need urgent attention.

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