1 April 2016

Landslides in Art Part 25: Richard Humphrey

Landslides in Art Part 25: Richard Humphrey

This version of the Landslides in Art series features a painting by the Californian artist Richard Humphrey.  He has a Bio on the Tirage Art website, as follows:

Richard Humphrey began his formal art education at the Art Center College of Design in Los Angeles in 1972. He then joined the staff of the Aerospace Corporation as a graphic designer, which provided him with a comprehensive background in design, illustration, and computer graphics. As a fine artist, Humphrey has focused on painting en plein air, concentrating on the area in which he was raised, California’s Palos Verdes Peninsula. Since 1997, Humphrey and fellow local artists have created hundreds of paintings to benefit the Palos Verdes Peninsula Land Conservancy in the preservation of the still undeveloped acreage in the area. California Museum exhibitions include: The Autry National Center, the Natural History Museum of Los Angeles County, the Bowers Museum in Santa Ana, the Carnegie Art Museum, the Pasadena Museum of History, the Pasadena Museum of California Art and the State Capitol Building in Sacramento. He is a Founding Member of the Portuguese Bend Artists Colony and a Signature Member of the California Art Club, where he was awarded the Edgar Payne Award for landscape painting in 2007.

The work I am featuring is a watercolour entitled ““Morning at Bluff Cove”, which was selected for the California Art Club’s 105th Annual Gold Medal Exhibition:-

Morning at Bluff Cove by Richard Humphrey

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The location is, I think, Bluff Cove on the Palos Verdes Estates Shoreline Preserve in California.  The bluffs of this section of coastline are renowned for active landslides.  The painting captures beautifully two examples.  On the leff the landslide appears to be a shallow translational slide, whilst on the right is a deeper seated landslide, perhaps with an element of rotational failure.

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31 March 2016

Pakistan: a highly destructive landslide caught on video

Pakistan: a highly destructive landslide caught on video

A new video has appeared on Youtube and Liveleak showing a landslide in Pakistan.  The slide appears to have started high up on the slope, but unfortunately the video quality is not good enough to ascertain properly what is happening.  It appears to accelerate rapidly down the lower slopes – but see below because the mechanism is more complex than it appears – and then crashes through a series of houses:-

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Taking a look at the video in a little more detail, clearly before the landslide appears on the lower slopes something is going on in the plateau area beyond the view of the camera.  The people around the camera were aware of this, and appear to be trying to warn those on the slopes below of the danger.  There is a lot of dust in the air at the top of the slope:-

Still from a Youtube video of a landslide in Pakistan

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It looks to me like the slope above the plateau is failing and moving, but it is hard to tell.  Could this be a quarry?.  About 27 seconds into the video, material starts to travel over the break of slope that marks the edge of the plateau, and it travels down the main slope.  Compare the image below with the one above:-

The development of the landslide in Pakistan – still from a Youtube video

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But what happens next is the most interesting element.  The debris flowing down the lower slope triggers another failure, probably in the deep soil and weathered rock that forms this area.  This is just happening in the still below:

The lower slope failure in Pakistan – still from a Youtube video

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It is this secondary failure that destroys the houses, leaving the deep landslide scar behind:-

The Pakistan landslide – still from a Youtube video

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Technically this is a combination of an induced failure and a rapid entrainment event.  It illustrates beautifully the complexity of landslides, and why it is so hard to forecast their behaviour.

Sadly there is no further information about this landslide – does anyone know any more?

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30 March 2016

Rockfall triggering on warm days in exfoliating landscapes

Rockfall triggering on warm days in exfoliating landscapes

Rockfall triggering is a complex process.  It is an interesting intellectual problem with which to grapple – what causes a block to detach at a specific moment in time?  Whilst the obvious suspects are of course water and wind; a less blatant factor is the growth of ice within a fracture or joint that can slowly widen the crack until detachment occurs.  And of course we know earthquakes are a key issue in those areas that are seismically active, but in many ways that is a different problem.

In the literature there are some suggestions that heating from the sun might also be a factor in landscapes subject to exfoliation.  For those who need a reminder, exfoliation occurs when the stress system allows joints to form that run parallel to the rock surface, allowing sheets or slabs of rock to detach.  There is a good explanation of this process on the Geological Society webpage, although in my view this overplays the role of chemical weathering. However, the evidence for the strength of this thermally-driven process is not good, so its importance has been hard to judge.

Yosemite is a landscape dominated by exfoliation, creating spectacular landscapes and frequent, potentially hazardous, rockfalls.  As such this is an ideal place to study thermally-driven crack widening in an exfoliating landscape.  In a paper just published by Nature Geoscience, Brian Collins and Greg Stock (Collins and Stock 2016) have investigated this process by monitoring, over a period in excess of three years, the displacement of a crack forming a large exfoliation joint in Yosemite.  This is excellent work using high precision crack meters, and sensors for other environmental conditions, shown below in a figure from the paper:

The exfoliation joint monitored for rockfall triggering – image from Collins and Stock (2016)

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The results are fascinating.  Collins and Stock (2016) show clearly that there is a strong daily cycle of temperature variation on the exfoliation surface as the block is heated by the sun.  In response, the crack widens, before narrowing again as the rock block cools back down:

Rockfall triggering by thermal expanision – permanent deformation in the crack induced by heating and cooling – figure from Collins and Stock (2016)

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But the most exciting element of this is that a component of the deformation is permanent – i.e. at the end of each cycle (each loop in the figure above) the crack is a little wider.  In fact the amount of permanent deformation in each cycle shown above is remarkably high – in the order of a millimetre on each occasion.  This level of permanent damage will only occur under ideal situations – i.e. in the middle of summer (note the date above in relation to the solar cycle) on a near cloudless day, but nonetheless the role of solar heating in causing permanent displacements in exfoliating landscapes is clear.  It is also worth noting the magnitude of the daily displacements, which are in the order of a centimentre.  This is a remarkably dynamic environment.

These results are scientifically wonderful, and they have implications for landscape evolution and rockfall hazards in other high mountain areas.  Whilst higher than expected levels of rockfalls have been observed in the summer months in many mountain landscapes, in general I think it has been assumed that this is mostly associated with the melting of ice in cracks.  Whilst this ice driven process is undoubtedly still important, Collins and Stock (2016) has given us cause to think about other processes too.

Reference

Collins, B.D and Stock, G.M. Rockfall triggering by cyclic thermal stressing of exfoliation fractures. Nature Geoscience. http://dx.doi.org/10.1038/ngeo2686

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29 March 2016

Sparmos Dam – a significant dam failure in Greece on Sunday 27th March

Sparmos Dam – a significant dam failure in Greece on Sunday 27th March

In Elassona, Greece the Sparmos Dam overtopped and breached in the afternoon of Sunday 27th March. Geotechpedia has a short article with some images.  There is a better set of images on the Michanikos.gr website.  An edited Google translation of the description is as follows:

Thousands cubic meters of water poured onto the plain of Elassona, destroying roads and fields with crops when the Sparmos dam broke on Sunday.  The surge of water, indeed, was such that it even dismantled the pavement.

The breach in the dam itself is quite dramatic:

An overview of the Sparmos Dam breach in Greece via Michanikos.gr

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Fortunately downstream damage appears to be light.  Note the shallow landslide on the inner face of the dam wall, on the right side of the embankment.  I suspect that this is a drawdown landslide, triggered by imbalanced high pore water pressures in the embankment when the water level rapidly dropped.  Michanikos.gr also has a close up of the breach itself:

Detail of the Sparmos Dam Breach via Michaikos.gr

It seems fortunate that the damage was not more serious.  EPT reports (in Greek) that there are plans to rebuild the damaged portion of the dam to restore its capability to store water.  It seems important to understand first how the overtopping event occurred.

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28 March 2016

A terrifying video of two coaches trapped by “shooting rocks” in Pakistan

A terrifying video of “shooting rocks” from the Karakorum Highway in Pakistan

Youtube has an amazing and terrifying video of two coaches trapped by “shooting rocks” – very high velocity rockfalls – on the Karakorum Highway in Pakistan.  These boulders, some of which are very large, have managed to get into the high velocity, bouncing mode that is so dangerous:

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Particularly impressive is the boulder at the 28 second point, shown below.  This boulder has entered the mode of movement in which it is rotating around its short axis, allowing very large bounces and high velocities to develop.  It is a good thing this did not strike the coaches:

Shooting rocks on the Karakorum Highway, via a Youtube video

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It is not clear as to where this occurred on the Karakorum Highway, but fortunately there were no casualties.  It must have been terrifying for those on the buses though.

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27 March 2016

Remarkable new footage of the mudflow from the Samarco tailings dam failure in Brazil

Remarkable new footage of the Samarco tailings dam failure in Brazil

An amazing new video has appeared on Youtube showing the mudflow that was released by the Samarco tailings dam failure in Brazil on 15th November 2015.  I covered this event at the time, and investigations continue into the cause and blame.  This video is accompanied by some text in Portuguese.  Google Translate, with some edits by me, renders this as follows:

In an unprecedented video posted by one of the witnesses of the tragedy on a social network can be seen the strength of brown mudflow that came down from the mountains, reaching and destroying communities and all that was ahead. The desperation is of the three people who were close to Bento Rodrigues, Mariana district of Minas Gerais Central Region, which was devastated by mud tailings  from the Fundão dam, on November 5, 2015

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Although quite distant, the extraordinary pace and power of the mudflow is clearly apparent:

A still from the new Youtube video of the Samarco tailings dam failure

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This is a video that all people responsible for designing and managing tailings dams should view.

Meanwhile, the enormous cost of this event is becoming more apparent.  BHP Biliton, co-owner of Samarco, has produced a website that outlines the work that they are undertaking in the aftermath of the disaster.   The Telegraph reports that the mine will reopen towards the end of the calendar year, with the tailings being stored in two pits whilst the dam is rebuilt.   O Globo reports (in Portuguese) that the tailings are damaging the ecosystem at the mouth of the Rio Doce, down which the mudflow travelled,  Meanwhile, sales of fish in Colatina are reported to have fallen as people are worried that they might have come from the polluted waters of the Rio Doce.

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24 March 2016

The Yale Himalaya Initiative landslide hazard map for Nepal

The Yale Himalaya Initiative landslide hazard map for Nepal

An article by the Yale Himalaya Initiative has announced the development of a new landslide hazard map for Nepal.  This map, below, was built by a team who “created a model to identify high-risk areas. Their model incorporated elevation, aspect, slope, roads, population centers, rainfall patterns, and drainage systems.”  It appears that this was based upon a more local scale approach used by ICIMOD.  The resultant map divides the country into four hazard classes:

The Yale Himalaya Initiative landslide hazard map for Nepal

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The article claims that the technique has remarkable skill in identifying areas of high hazard.  One of the team, Ross Bernet, is quoted as saying:

“Our model is 84-percent accurate based on the data we had…We’ve said, ‘Here’s where we found the data, here’s what we’re working with, here’s what we did.’ The hope is that someone who might be using the map to make decisions that affect people’s lives really understands all of that.”

On the face of it this is very laudable, but I have reservations.  think a few key points are pertinent here.  The first is that one needs to be very careful to define terminology.  In particular, the use of the terms hazard and risk have particular meanings in this context, and they should not be used interchangeably.  It is far from clear to me as to whether this is a hazard map or a risk map (the inclusion of population centres may indicate the latter?), or maybe a susceptibility map.  Second, it is really important to be clear about which type of landslide trigger is being discussed.  Seismically-induced landslide hazard will be different from that for rainfall, so which is being accommodated here?  Given that seismic hazard is not included as an input, it would seem it is just rainfall induced landslides, but the inset map suggests that the landslide inventory was for seismically-induced failures. And third, great care must be taken with statements about accuracy.  I could decide that all of Nepal is high hazard, and claim to be 100% accurate because all of the landslides are in my high hazard zone.  But this is meaningless of course.  Defining what is meant by accuracy is really important.  We must not get into a situation in which decision makers think we can assess the hazards of landslides with very high levels of accuracy.  We simply cannot at present, and that is not for a lack of trying.

A second key issue for me is that this work appears to be presented in isolation.  Bu this is not the first national scale landslide map for Nepal.  The Nepal Hazard Risk Assessment (NB the link is to a PDF) project of a few years ago, which was led by a very credible and experienced international team who really understand both landslides and risk, undertook a detailed assessment of a range of hazards in Nepal, including landslides.  They generated two maps of national landslide susceptibility (not hazard or risk).  This one for rainfall-induced landslides:

The Nepal Hazard Risk Assessment Project map of rainfall induced landslide susceptibility

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And the other for seismically-induced landslide hazard:

The Nepal Hazard Risk Assessment Project map of seismically-induced landslide susceptibility

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There are huge differences between these two maps of landslide susceptibility, and between these maps and the one generated by the Yale Himalaya Initiative.  There is a real danger of confusion here, which I find very worrying.

I have been collecting data on landslides that kill people in Nepal for 16 years.  Technically this is of course the realisation of landslide mortality risk (and I note that the Nepal Natural Hazard Risk project maps do not show risk – I am unsure as to whether this aplies to the Yale Himalaya Initiative map as well), .  Below is a map of fatal landslides across Nepal for example from my data (these are all rainfall-induced landslides):

Map of fatal landslides in Nepal from my fatal landslide database

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There is a notable difference in the location of these landslides and the landslide hazard map from the Yale Himalaya Initiative.  The Nepal Hazard Risk Assessment Project appears, at least superficially, to explain the distribution much better.

I realise that I might sound overly critical in this post – that one could take the view that every initiative of this type is a good thing.  And I recognise that this work is built upon the strengths of ICIMOD.  But releasing a map into the wild like this without providing an explanation for what it actually shows and how it was derived feels unhelpful.  This feels even less satisfactory when high levels of accuracy are claimed but are not explained or justified.

Landslide hazard mapping is deeply challenging.  There are no simple fixes in my view,

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22 March 2016

Multiple landslides in the last few days in northern India and Pakistan

Damage to houses in Pakistan caused by one of multiple landslides in the last few days, via Dawn

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Multiple landslides in the last few days in northern India and Pakistan

Heavy rainfall in the last few days in northern India and Pakistan has triggered extensive landsliding, resulting in surprisingly high losses.  Whilst this is an area that receives Spring rains, multiple landslides to this degree are not normal, it being some months prior to the development of the southwest monsoon.  Key incidents include:

1. Susam, Chitral, Pakistan

A mudslide triggered by heavy rainfall killed eight ninth grade students returning from exams.  Some reports have suggested 9 or 11 fatalities, and there is some confusion over whether this might have been an avalanche.

2. Ramsu area of Ramban district, Jammu and Kashmi, India

Five people died, and three were injured, when a taxi was knocked off the road and into a river by a rockfall.

3. Multiple landslides on the Jammu-Srinigar highway

Reports indicate that the road between Jammu and Srinigar was closed by landslides at Sher Bibi, Panthyal, Battery Chashma, Marog and Anokhi Fall, trapping more than a thousand vehicles.

4. Multiple landslides on the Doda-Batote highway

A massive landslide at the Raggi Nullah blocked the sole highway linking these twin districts.  Reports suggest hundreds of vehicles were trapped.

Damage to a house in Pakistan caused by one of the multiple landslides in the last few days, via Dawn

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5. A rockfall at Sarli Sacha Sharqi village

Five people, including four children, were killed when a boulder flattened a house in Sarli Sacha Sharqi village, in Pakistan’s Azad Jammu and Kashmir, late on Friday night. One child survived.

6. A landslide at Ochar Mohalla in Bagh District

A couple were killed by a landslide at Ochar Mohalla on the outskirts of Bagh City. A child survived the landslide.

7. Multiple landslides in Murree in Pakistan

Reports suggest that the Murree area of Pakistan has also been very badly affected by landslides.  Dawn reports that “Almost half the village of Graan-Ghoe was destroyed when a landslide damaged 30 homes, and the residents have no other choice but to wait out the rain under the open sky.  Houses were also destroyed in Potha, Sehana, Phagwari, Aloit, Sehrbagla, Masot, Dewal and Phaphril among other villages, where roads and other infrastructure worth billions of rupees was also damaged.”

8. A fatal landslide at Jaglote in Gilgit

A woman was killed in a fatal landslide at Jaglote.  Pamir Times reports that: “huge boulders fell from a nearby mountain hitting several houses and cattle sheds. As a result a woman was killed. Around a dozen sheep, goats and cows, other cattle, were also killed. Three houses were damaged.”

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20 March 2016

Chelan County: A landslide near Wenatchee triggers evacuations

Chelan County: A landslide near Wenatchee triggers evacuations

Near to Wenatchee in Chelan County, Washington State, in western USA, a large landslide has developed that is directly threatening 26 houses, leading to the evacuation of a number of families.  KOMO News has the best account of this landslide:

Neighbors in the area have been asked to evacuate as the ground continues to shift and officials try to figure what has caused the potentially deadly disaster.  Just above Wenatchee, the Whispering Ridge neighborhood provides a mountain top perspective. … Residents in 26 houses have been advised to leave. Roughly a dozen could take a direct hit from what has been described as a “potential massive landslide.” Two homes have already been declared unsafe to live in.

This landslide appears to have developed over the last few months at least, but to have become acute in the last few days, perhaps in response to recent heavy rainfall.  KOMO News has a gallery of images of the landslide, including these two showing tension cracks running close to houses:

Chelan County landslide via KOMO News

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Chelan County landslide via KOMO News

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The location of this landslide appears to be the area on the map below:

Chelan County landslide location

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A Google Earth perspective view gives a better impression of the landscape in which this landslide has developed:

Chlean County landslide: a Google Earth perspective view

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The news reports suggest that there is now a geotechnical investigation of this site to determine the causes of the landslide.  Washington State is of course prone to landslides, and indeed on the image above there is a very prominent landslide scar on the left side, and hints of others too.  But the immediate cause of this landslide is less obvious. The Google Earth imagery extends back to 1998.  In the intervening time there have been some minor changes to this area, but nothing obviously sufficient to trigger the landslide.  The two ponds higher up on the slope, for example, were both present in 1998.

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17 March 2016

The Val Strem rockslide – a dramatic long run out landslide in Switzerland

Val Strem rockslide

The Val Strem rockslide occurred on Monday night in Canton Graunbunden in Swtizerland.  This large rockslide appears to have had a dramatically long run out given its volume.  There are a number of good reports about the landslide (in German) on the web, with some very high quality images.  This one, via RTR, provides a nice overview of the landslide:

The Val Strem rockslide via RTR

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There are a number of interesting features of this rockslide.  The source of the collapse, which had a volume of about 200,000 cubic metres, was high on the valley wall on the right.  The debris has slid down, super-elevated on the opposite valley wall, turned 90 degrees and then travelled down the main valley.  Note the dust mantling the opposite valley wall.  The landslide appears to have been very mobile (the estimated runout is about 1 km) – this is not really captured in the image above, but this one, also from RTR, shows it much more clearly:

The Val Strem rockslide via RTR – detail of the runout

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Reports suggest that the source of the rockslide, the Cuolm is da Vinci, was known to be unstable and had been monitored.  It will be interesting to see what the data shows.  The long runout might be explained by the fall onto a layer of snow, which might have provided a low friction surface.  However, the snow depth does not look large to me, so I have some doubts about this.  It could have been the effects of a frozen ground surface, but I suspect that a more important factor might be the constant valley gradient, which may have been sufficient to keep the debris moving.  Interestingly, the landslide does appear to have been losing mass (depositing material) the whole way along its track.  The image below, again from RTR, shows the upper part of the track in more detail – note the coarse material in the centre of the track, with finer grained material on the margins:

The Val Strem rockslide – detail of the track via RTR

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Note the dust cloud from ongoing slides in the background.  The Val Strem rockslide did not cause any loss of life or damage to property, but it has damaged the water supply the local communities and the inlets for a small hydro-electric plant.

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