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24 June 2019

Salaks: an unusual video of a landslide impact in Norway

Salaks: an unusual video of a landslide impact in Norway

On 8th June 2019 a landslide struck the Salaks salmon processing plant in the northern part of Norway, severely damaging the building and some of its equipment, and shutting the works down.  Various news agencies reported the story in Norwegian at the time.  Some included this image of the aftermath of the site:-

The landslide that damaged the Salaks plant

The landslide that damaged the Salaks plant in Norway. Image by Universitetssykehuset Nord-Norge via NRK.

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The failure appears to be a collapse of a rock bluff above the plant, with the debris following the slope to the bottom of the hill.  There is some entrainment, most notably of trees.  The landslide appears to have struck the corner of the plant.

Salaks have released CCTV video of the landslide striking the Salaks factory.  It includes two different views, one within the building and one from a camera mounted outside.  Unfortunately I cannot embed this video, but if not it can be viewed here.   It is worth a look.

The landslide at the Salaks plant

The landslide at the Salaks plant in Norway. Still from a video of CCTV footage released by the company. The video can be viewed on the Intrafish website.

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Although this is a comparatively small landslide, the violence and power of the event is clear. It is fortunate that there was no-one in the path of the landslide.

The news reports indicate that Salaks are still not able to enter the building, and so the full extent of the damage is not yet established.  It is the second blow to the company this summer, which has been facing the impact of an algal bloom, damaging its fish stocks.  The plant has about 25 employees in total, none of whom are able to work at present.  Reports suggest that these individuals have had to be temporarily laid off.

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21 June 2019

Debris Flow Hazards Mitigation: Mechanics, Monitoring, Modeling and Assessment

Debris-flow hazards mitigation : mechanics, monitoring, modeling, and assessment

Debris Flow Hazards Mitigation: Mechanics, Monitoring, Modeling and Assessment

Earlier this month, from 10th to 13th June 2019, the Seventh International Conference on Debris-Flow Hazards Mitigation was held in Golden, Colorado. This was a substantial meeting focusing on the mechanics, monitoring, modeling and assessment of this very major hazard.  Only yesterday I highlighted a serious debris flow disaster in the Trabzon region of  Turkey.  According to the organisers of the conference, the aim of major objective of the meeting was to provide a forum for international researchers, engineers, and policy makers to exchange ideas and promote communication to advance the scientific understanding of debris-flow hazards as well as approaches to assess and mitigate debris-flow risk to infrastructure and people.  It looks to have been an excellent event, which included 14 keynote presentations, 38 presentations and 86 posters.

Remarkably, the conference hosts have posted the proceedings of the meeting online, free to download.  The volume consists of 134 papers looking at all aspects of debris flows.  There are some detailed case studies; analyses of past and historic events; simulations and models; physical experiments; and descriptions of mitigation approaches.  Some of the papers examine events that I have described on this site, such as the 2018 Montecito debris flows in California, whilst others look at events that are new to me.  The quality of the papers is very high, and there are some fascinating contributions.

The organisers have kindly posted the various sections of the volume separately, as well as a single PDF for the entire volume.  These are listed below:-

This is a very helpful record of the state of the art in debris flow science and engineering.  The next meeting the Eighth International Conference on Debris-Flow Hazards Mitigation will be held in Turin, Italy, presumably in 2023.  Details will be available in due course.

Reference

Kean, J.W., Coe, J.A., Santi, P.M. and Guillen, B.K. 2019.  Debris-flow hazards mitigation : mechanics, monitoring, modeling, and assessment. Proceedings of the Seventh International Conference on Debris-Flow Hazards Mitigation, Golden, Colorado, USA, June 10-13, 201. Association of Environmental and Engineering Geologists, Special Publication 28.

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20 June 2019

Arakli: devastating debris flows in Trabzon province in Turkey yesterday

Arakli: devastating debris flows in Trabzon province in Turkey yesterday

Intense rainfall yesterday (19th June 2019) in Trabzon province in Turkey triggered a series of devastating debris flows in the hilly Arakli area close to the Black Sea coast.  News reports suggest that seven people are known to have died in the disaster, and a further seven people are missing.  Worst affected appears to be the communities of Çamlıktepe and Yeşilyurt, in the Arakli area, where reports suggest that ten lives have been lost. This image, from mynet.com, gives a good perspective of the aftermath of one of the affected areas:-

The debris flows at Arkali

The aftermath of one of the debris flows at Arakli in Trabzon, Turkey. Image via mynet.com

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There are some images available via Twitter that show this site during the main part of the event:-

The debris flow at Arkali in Turkey

An image, posted to Twitter, showing the debris flow at Arakli in Turkey on 19th June 2019

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There is also a short video on Twitter that appears to show the arrival of one of the debris flow waves.  This is an uncomfortable video to watch as the terror of the person filming the event is very clear.

There is an article in English on the Daily Sabah about this event.  Interestingly, it suggests that the debris flows may have been associated with landslides upstream:-

“Interior Minister Süleyman Soylu, who was a former lawmaker from Trabzon, joined Agriculture and Forestry Minister Bekir Pakdemirli for a visit to the flooded areas yesterday. Soylu told reporters that the epicenter of the disaster was the confluence of two rivers and heavy rainfall hitting a hill where the neighborhoods are located triggered landslides.”

However, there is also a strong suggestion in the Turkish media that a hydroelectric scheme located upstream may also have played a role, although it is not clear to me as to how this might have occurred.  Images over the next few days may shed light on that, although further rainfall is forecast.

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18 June 2019

The Global Fatal Landslide Database: full dataset now online

The Global Fatal Landslide Database: full dataset now online

Thanks to the hard work of Dr Melanie Froude, my colleague here at the Department of Geography at the University of Sheffield, we have now posted the full Global Fatal Landslide Database online.  This is the dataset that underpins our paper of last year (Froude and Petley 2018) that explored the human cost of landslides from 2004 to 2016 inclusive.  However, this new version adds a further year of data, covering 2004 to 2017 inclusive.

The dataset can be accessed via an ARCGIS web application, which allows mapping of the dataset at a range of scales.  The full dataset looks like this:-

Map of the Global Fatal Landslide Database

A simple map of the Global Fatal Landslide Database.

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Whilst the application allows mapping at the national scale – this is the area around Nepal for example:-

GlobaMap of the Fatal Landslide Database

The Global Fatal Landslide Database: an example of a national level map – the distribution of fatal landslides in the area around Nepal.

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And more detailed mapping is also possible – this is the distribution of fatal landslides on the island of Java in Indonesia:-

Global Fatal Landslide Database

An example of a map from the Global Fatal Landslide Database – the distribution of fatal landslides on the island of Java in Indonesia.

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Over the last couple of years, Melanie has remapped all of the landslides to verify their locations.  In each case a polygon has been constructed that define the area in which we believe that the landslide has occurred.  In some cases this polygon defines the landslide itself; in others it defines for example the village in which the landslide happened (where this is the most precise description that we have found).  The mapping tool allows you to display this data, or the centroid of the polygon to generate a point.

Melanie has written a guide to the dataset, which can be found here:

https://drive.google.com/file/d/1FGI4cQuykv_CqPSd2Fe_x0Djqc6K8XWh/view

This provides full details of the dataset, and of course its limitations.

Perhaps most importantly, the full dataset is now available to download.  The manual provides detail of how to do this, via a free public ARCGIS account.  We have released the data as an asset for free public use. However, please acknowledge the following open source license and acknowledge the source of the data by citation.  The dataset is covered by a University of Sheffield copyright and database rights reserved 2019. For the full license see
http://www.nationalarchives.gov.uk/doc/open-government-licence/version/2/

When using data in a publication, please cite the following reference:

Froude, M. J. and Petley, D. N. 2018. Global fatal landslide occurrence from 2004 to 2016. Natural Hazards and Earth System Science, 18, 2161-2181, https://doi.org/10.5194/nhess-18-2161-2018.

This paper is open access, so should be accessible to all.

If you are struggling to download the data, it is also temporarily available via a Google Drive folder:-

https://drive.google.com/open?id=1kxUSXBl10OHPrGXIur6bM4PBoKX0C_LY

This contains zipped shape files for each data layer.

Melanie and I hope that you will find both the web app and the dataset to be useful.  Putting this dataset together has been a huge piece of work, which I started in September 2002 and continue today (so almost 17 years, and counting), whilst the mapping of the landslides, and the collation of the dataset, has been thousands of hours of work by Melanie.  However, we believe that the effort has been worthwhile, and the work will continue for the foreseeable future.

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17 June 2019

Longyan City: a dramatic landslide in deeply weathered soil

Longyan City: a dramatic landslide in deeply weathered soil

On 13th June 2019 a strong rainstorm struck Longyan City in Fujian province, southern China, triggering a major landslide that was captured on CCTV. The video has been widely shared online, and is available on Youtube:-

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This is just one of many rainfall-induced incidents across southern China, with reports on the BBC suggesting that up to 61 people have been killed.  The landslide in Longyan is reported to have killed one person, who was sitting in one of the cars.

The still from the video below catches some of the key features of the landslide:-

Longyan City landslide

The large landslide at Longyan city in Fujian Province in Xhina on 13th June 2019. Still from a video posted on Youtube by Xinhua / New China TV.

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The video shows that the landslide was very highly mobile, implying that the soil has undergone liquefaction during failure. The material is a deep red colour, implying that it consists of deeply weathered soil and regolith, which is not unusual in the humid, subtropical climate of the southern part of China.  The interaction between the landslide and the vehicles is interesting – note that they are pushed forward by the landslide rather than being buried or inundated.  This illustrates the points that I made a dacade ago about rescuing the victims of landslides.  It is crucial to understand the landslide mechanism and type of flow as many (but by no means all) landslides tend to bulldoze objects in their path, rather than burying them in situ.

In this case it will be interesting to understand better the underlying causes of the landslide.  The failure appears to have swept down a slope that is at least partially vegetated, although that vegetation does not look like original forest to me.  I wonder if the slope was but in order to create the bench for the road?

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13 June 2019

Sidestrand: a complex coastal cliff landslide captured on video

Sidestrand: a complex coastal cliff landslide captured on video

Many media outlets have been featuring a video from Sidestrand in Norfolk, eastern England, showing a complex landslide event.  This video was posted to Facebook by Brad Damms.  It can be accessed here:

Whilst working on a timelapse monitoring project for scanLAB projects this morning at Sidestrand! A huge cliff fall. After all this rain the cliffs are very unstable! Please stay away from the cliffs, the authorities have been notified.

Posted by Brad Damms on Wednesday, June 12, 2019

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There is a good guide to the geology of this area on the Norfolk Project webpages, and the BGS have a good page about this site as well.  In essence, the cliffs are composed of highly complex glacial deposits, mostly consisting of glacial till but including rafts of chalk.  There are classic, and very beautiful, glaciotectonic folds found in the materials.  The combination of weak, deformed materials and the storminess of the North Sea (which has a very high tidal range) means that these cliff are very susceptible to landslides.  The BGS note the following in terms of landslides in this section of coastal cliffs:

The landslides at the Sidestrand test site are complex, consisting partly of large-scale, deep-seated landslides and partly of mudslides and debris flows. The deep-seated movements tend to have a dominant rotational component, but are in part translational. In some cases these extend to depths several metres below platform level, but are more usually entirely within the cliff. The landslides form deeply incised embayments which are arcuate in plan. The backscarps at the cliff-top tend to be sharply defined vertical features which persist after the landslide event. Deep-seated landslides tend to rotate to angles of 10 to 20 degrees and break up during failure transport, producing large debris aprons which spread across beach and platform. These are short-lived as the debris is readily removed by the sea. Such large events are followed by many mudslides and mudflows.

The event captured in the video above shows many of the characteristics of these landslides, with sequential cliff collapses transitioning into flows that have, in some cases, quite high mobility:-

Sidestrand landslide

A still from the video of the Sidestrand landslide in Norfolk. Video posted to Facebook by Brad Damms.

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The video was captured by Brad whilst undertaking scanning of the cliffs for the scanLAB project.  It will be fascinating to see what the scans show.  The UK has just experienced a prolonged period of unusually heavy rainfall.  This is likely to have been the immediate trigger for this event, although of course the underlying cause is wave erosion at the toe of the slope.  This section of coast loses up to 3 m of land per year on average.

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12 June 2019

The 2017 Nayong rock avalanche: an analysis using drone and seismic data

The 2017 Nayong rock avalanche: an analysis using drone and seismic data

On 28 August 2017 a catastrophic landslide (now known as the Nayong rock avalanche) occurred in Guizhou Province, China, causing multiple fatalities.  I covered this event at the time, noting that remarkable footage had been collected of the event both from the ground and, astonishingly, from a drone.  This rock avalanche has been analysed in detail in a new paper (Zhu et al. 2019) published in the journal Engineering Geology.  Interestingly, the authors have combined the seismic data with the drone video to understand the dynamics of the failure.  I believe that this is the first time an analysis like this has been undertaken.

This is an image from Zhu et al. (2019)  showing the aftermath of the Nayong rock avalanche:-

The Nayong rock avalanche

The aftermath of the Nayong rock avalanche. Image from Zhu et al. (2019).

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The image shows that this was a catastrophic collapse of a limestone rock slope. The landslide occurred as five discreet events recorded by the drone, with the fifth being the largest. According to Zhu et al. (2019), this had a volume of about 490,000 m³, which then entrained a further 310,000 m³ from the slope.  The rock avalanche descended a total vertical distance of 280 m, and travelled for a total distance of 820 m.  It killed 35 people.

I think the most interesting aspect of this paper is seen in the seismic signal, and corroborated by the drone footage:-

Seismic signal from the Nayong rock avalanche

The seismic signal generated by the Nayong rock avalanche in China in 2017. Diagram from Zhu et al. (2019).

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The seismic signal shows the first detected collapse event occurring shortly before 10:18, before the first major event, seen in the drone footage, just after 10:20. The seismic signal shows that the landslide was generating a series of small seismic signals, which are presumably indications of fracture and collapse occurring within the landslide mass as it began to fail.  We have seen this pattern previously, and once again emphasises that rock slope failure is a time dependent process in which the final collapse is simply the final manifestation of long-term deformation and rock fracture.  It is this phenomenon that allows the forecasting of some rock collapse events, if suitable instrumentation is deployed.

Reference

Zhu, Y., Xu, S., Zhuang, Y., Dai, X and Xing, A. 2019. Analysis of characteristics and runout behaviour of the disastrous 28 August 2017 rock avalanche in Nayong, Guizhou, China. Engineering Geology. Doi: https://doi.org/10.1016/j.enggeo.2019.105154

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11 June 2019

Three new landslide videos

Three new landslide videos

Three good landslide videos have been posted to Youtube, all of which are worth a look.  We are now moving into the rainy season across much of East and South Asia, meaning that landslide occurrence is increasing.

An impressive landslide in Fujian, China

This landslide, posted by New China TV, reportedly occurred in Sanming in Fujian in China.  The reports indicate that it was triggered by heavy rainfall:-

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This still seems to suggest that the landslide initiated on a steep slope that had been cut at the toe.  Note the slope reinforcement on the lower part of the slope.  It is also interesting to note the presence of the electricity pylon, which appears to be close to the crown of the landslide:-

The landslide at Sanming in China

The site of the landslide at Sanming in Fujian, Chine. Still from a video posted to Youtube by New China TV.

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A large landslide in the mountains of Hunza, near to Attabad in Pakistan

Northern Areas of Pakistan has posted a nice video of an apparently large landslide in the Bulbul Kešk area of Gulmit in Gojal-Hunza in northern Pakistan, which occurred on 4th June 2019.  The report indicates that the toe of the landslide reached Attabad Lake, causing the boat service to be suspended.  Understandably, given the experience at Attabad nine years ago, this has caused a great deal of concern in the area.

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A mobile landslide in Himachal Pradesh, northern India.

Finally, Khabar Bharat has posted a nice video of a much smaller but quite mobile landslide in Kullu District in the Karsha area of Himachal Pradesh in northern India:-

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This landslide reportedly blocked the NH305 road between Aani and Luhri.  Interestingly, the landslide appears to have occurred in dry conditions (note the large amounts of dust generated by the landslide). Slope cutting for the road might have been a key factor here.

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10 June 2019

An image of the state of the Hidtroituango powerhouse

An image of the state of the Hidtroituango powerhouse

A year ago I wrote several times about the major problems being faced by the operators of the Hidroituango dam in Colombia, which had suffered from significant landslides and rock mass failures, which in turn drove emergency works to complete the embankment to allow the spillway to be used to manage the lake level.  One effect was flooding through the cavern housing the turbines.  Since then it has been quite challenging to understand properly the state of play with this facility as work continues to repair the damage.  Images have emerged at various points showing the state of the Hidroituango powerhouse, all of which seemed to show substantial levels of damage.  Last week, Patricia Garip, an independent journalist, published on Twitter what appears to be the definitive image of the condition of the facility.  It is quite shocking:-

The Hidroituango powerhouse

Image of the state of the Hidroituango powerhouse in June 2019. Image posted to Twitter by Patricia Garip.

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Clearly the level of damage is high, with complete destruction to much of the concrete infrastructure, and heave damage and erosion to the remainder.  At the far end of the cavern there is a very substantial debris accumulation.  It is not clear to me as to whether this is a collapse of the rock mass or sediment deposited as a result of the flooding.  Interestingly, there also appears to be considerable amounts of water present on the ceiling and walls of the cavern. I wonder why.

The authorities responsible for Hidroituango continue to assert that the damage to the site is repairable, and that Hidroituango will be generating electricity by 2021.   Works continue to seal the various tunnels to secure the site, allowing full restoration to proceed.  However, some questions continue to be asked about the integrity of the rock mass through the mountain, especially in light of the landslide problems at the site.

I would be interested in comments from those who know more about the true picture of this key project.

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30 May 2019

High resolution Planet Labs SkySat image of the Joffre Peak landslides

High resolution Planet Labs SkySat image of the Joffre Peak landslides

Planets Labs have kindly captured a high-resolution SkySat image of the Joffre Peak landslides:-

Joffre Peak landslides

High resolution Planet Labs SkySat image of the Joffre Peak landslides. Planet Labs SkySat image, captured 28th May 2019, Copyright Planet Labs, used with permission.

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This is a beautiful image, capturing the track of the landslide in full.  Note that there are some distortions in the source area, an artifact of the processing of an oblique image to a vertical view.  Of course there are better ways to capture imagery of very steep slopes than the use of satellite images.  But, importantly, the track is fully imaged.

Perhaps the most interesting aspect of this image is the mid track section of the Joffre Peak landslides site:-

Joffre Peak landslides

High resolution Planet Labs SkySat image of the main track of the Joffre Peak landslides. Planet Labs SkySat image, captured 28th May 2019, Copyright Planet Labs, used with permission.

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In my earlier post I noted that there was little evidence of super-elevation in the lower bend of the landslide track (super-elevation occurs when fast-moving landslides travel around sharp corners; the landslide debris travel up the valley wall, much as a racing car moves to the top of a banked level of track).  My interpretation of the image is that the landslide does appear to have undergone significant super-elevation around the first bend (in which it changed from a track towards the northeast to one towards the east).  The evidence for this is the stripped slope, brown in colour and thus probably soil and weathered bedrock and rather than landslide debris.  The landslide has stripped the trees from the slope.

There is a small amount of super-elevation in the first part of the second bend (where the track changes from eastwards to northwards), but much less than upstream.

The implication is that the Joffre Peak landslides were moving rapidly in the upper portion of the track, but more slowly when they hit the second bend.  Immediately after the second bend there is a large area of deposition.  Interestingly, there is also a considerable amount of deposition in the upper portions of the track.

Once again the high resolution imagery provides very clear insight into the landslide processes.

Reference and acknowledgement

Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA.  Thanks to Robert Simmon of Planet Labs for obtaining and processing the image.

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