4 August 2015
Landslide sessions at the 2015 AGU Fall Meeting
NH015: Landslide Hazard, Vulnerability and Risk Analysis
Session Description: Landslides, while often smaller in scale relative to other natural hazards, impact nearly every country in the world and cause thousands of fatalities each year. This session will explore the multi-faceted topic of landslide hazard, vulnerability and risk through the use of remotely sensed, field-based, in situ investigations and modeling. Contributions are welcome on i) data and model uncertainty and quality assessment and ii) vulnerability, risk and cost evaluation of landslide hazards. Presentations may concentrate on innovative procedures for hazard and risk assessment, model development and validation, socio-economic surveys and case studies.
Primary Convener: Dalia Bach Kirschbaum, NASA Goddard Space Flight Center, Hydrological Sciences Laboratory, Greenbelt, MD, United States
Conveners: Paola Reichenbach, Hiroshi Fukuoka, and Dave Petley.
NH016: Landslide mechanisms, modeling and prediction
Session Description: Slope movements pose serious hazards yet are difficult to predict: several physical processes are coupled and operate on different time and spatial scales; materials are heterogeneous and their behaviors complex; the phenomena are transients; triggering is poorly understood. This session aims to bring together innovative research results from a variety of different approaches to understanding mass movement processes. In particular, we encourage presentations on physical modelling, innovative laboratory research, theoretical studies on the physics of multiphase and multiscale phenomena and detailed field observations, which yield insight into the triggering mechanisms, the mass movement or mass flow process. Presentations are also welcome on uncertainty and sensitivity analysis of modeling processes and landslide hazard prediction.
NH001: Advances in Analysis and Prediction of Rock Falls, Rock Slides, and Rock Avalanches
Session Description: Rock slope failures are among the most widespread and damaging rapid mass movements affecting mountainous areas, resulting in significant loss of life and property across the world each year. They also represent a potent erosional force capable of efficiently modifying landscapes. Modern hazard analyses demand deeper understanding of the triggering, failure mechanisms, and runout processes of rock slope failures. We invite novel contributions on rock falls, rock slides, and rock avalanches that either advance existing methods of analysis or present new understanding of phenomena. Topics may include theoretical and analytical developments, field and laboratory studies, monitoring strategies, geochronology, analytical and numerical modeling, or new methods in hazard assessment.
3 August 2015
The Fukaminato River landslide in Kyushu, Japan
Last week I highlighted the ongoing landslide on the Fukaminato River in Japan, including a video of one of the most recent failure events. There is now a better version of the video available on Youtube:
The video seems to show the main collapse event, including the initial sliding and the dramatic fragmentation of the landslide mass and, later on, the arrival of the debris flow wave downstream. There is also seem quite excellent drone footage of the site, collected from before the most recent failure, also on a Youtube video:
The drone footage provides a good overview of the landslide site, first looking upslope at the failure zone and upper reaches of the debris track:
And second, looking downslope along the debris flow track. Note the plume of sediment in the bay:
The Fukaminato River landslide is located at 31.590N, 130.795E. This is a perspective view of the landslide site, taken in 2010 via Google Earth:
Note the very extensive amount of quarrying that has been undertaken in this area, including at the landslide site. However, the active quarrying does not now seem to be occurring where the failures have been initiated. Perhaps the old quarrying work left the slopes in an oversteepened condition? The trigger appears to have been initiated by the prolonged heavy rainfall that this area has suffered over the last few weeks.
The Fukaminato River landslide site is close to Sakurajima volcano, which is currently very active. Whilst there is no apparent link between the volcano and the landslide, I cannot resist including some of the amazing videos of the explosive eruption of Sakurajima:
Thanks to Colin Stark of the Lamont-Doherty Earth Observatory at Columbia University, who did almost all the work that went into this post.
31 July 2015
Kaski and Myagdi landslides
Heavy monsoon rainfall yesterday triggered landslides in Nepal, most notably in Kaski and Myagdi districts, killing over 30 people. Landslides also occurred in Baglung and Chitwan. The map below is from Petley et al. (2007), which looked at monsoon landslides across Nepal. The dark colours indicate those areas most affected by landslides. I have highlighted in red the four districts hit by landslides yesterday:
Worst affected was Kaski District, which is very landslide-prone. The landslides that caused loss of life include:
- 19 fatalities in a landslide at Majhgaun in Lumle
- Five fatalities in a landslide at Bhadure Tamagi
- Two fatalities in a landslide at Dhikurpokhar
- Seven fatalities in a landslide at Mudi and Muna Villages
- One fatality in a landslide at Rayadanda
- One fatality in a landslide at Siddhi
Meanwhile the road between Pokhara and Baglung was also blocked by landslides.
The landslide at Lumle is particularly interesting. Ekantipur describes it as follows:
“Our correspondent in Kaski said 23 people, including seven of a family, died while six others went missing at Majhgaun in Lumle-6. The casualty was high as a water tank with the capacity of 20,000 litres was swept just above the settlement. Ten houses were buried. Local people and security personnel rescued three people immediately after the disaster.”
Note that different reports suggest different numbers of fatalities. Hopefully this will become clearer in the days ahead. Whilst it is tempting to link this to the earthquake, this is looks like just a normal monsoon rainfall event, the sort that happens every year. So far we are not seeing anomalously high levels of landslides, primarily because the monsoon is very weak. This graph shows rainfall through the first half of the month in Kathmandu versus the average (from My Republica):
On average July is the month with the heaviest rainfall in Nepal, but there is so much inter-annual variation that it should not be assumed that we are out of the woods as yet.
Meanwhile, the USGS has produced an excellent report on the earthquake induced landslides in Nepal. This is an invaluable resource.
Petley, D.N., Hearn, G.J., Hart, A., Rosser, N.J., Dunning, S.A., Oven, K., and Mitchell, W.A. 2007. Trends in landslide occurrence in Nepal. Natural Hazards 43:23–44.
29 July 2015
Two new landslide videos
Two new landslide videos are now available. Unfortunately I cannot embed either, so you will need to follow the links. You won’t be disappointed!
1. A dramatic rockfall in Taiwan
The image above is taken from an amazing video of a complex rock topple / rockslide from Taiwan. The link to the video is as follows (note that this is to a Facebook page):
This is a terrific video, showing both the power and volume of a large rockfall. Judging by the geology this is from the eastern side of central or southern Taiwan, I’d imagine probably the Southern Cross Island Highway, but possibly the Central Cross Island Highway. The caption suggests that the crack in the slope was observed by a highway engineer and the road closed. If so, well done that person! I have seen the aftermath of cars being caught in an event like this on the Central Cross Island Highway on several occasions. The video will be worth detailed interpretation in the way that it shows precursory rockfall activity before the final failure, which is likely to be an indication of the way that the rock mass was straining and deforming as collapse progressed.
2. The Fukaminato River landslide in Japan
In Japan, a large landslide is causing considerable problems along the Fukaminato River in Tarumizu City, Kagoshima Prefecture. This landslide has had three large failures in the last month, of which the most recent occurred yesterday. This landslide was caught on video – and well, what can I say. The link is as follows:
The very dramatic fragmentation of this landslide, and the extremely rapid runout, are fascinating. I hope to write about this again in the next few days.
Thanks to Colin Stark of the Lamont-Doherty Earth Observatory at Columbia University for highlighting this one.
23 July 2015
Ambunti, Papua New Guinea
Via Twitter, Dr Phil Collins of Brunel University (@PhilCollins_UK) highlighted an interesting story on an Australian news website about a “sinkhole” that developed on Saturday on the banks of the Sepik River in Ambunti, Papua New Guinea. The original news report has some images:
Pacific Islands Report has a longer description of the landslide:
According to witnesses Jamie Asa and Frank Warakai, the sinkhole formed about midday last Saturday at the Forex Camp and Saksak Compound, along the Sepik River. “Sixteen houses went down as the earth opened up unexpectedly.
“The settlers panicked and scrambled out of their houses within minutes as the earth shook,” a shocked Warakai said, adding that his house was the first one to be sucked in by the sinkhole.
He said he was woken from his sleep by the movement of the earth and jumped out of his house. As he ran for safety, the earth gave way within seconds, causing a large stretch of land to immediately sink in, creating huge cracks that destroyed houses. Mr Asa said the people in the settlements also panicked and many managed to escape to higher grounds. He said the displaced people are seeking shelter in makeshift houses and at nearby villages.
Whilst this is being reported as a sinkhole, I am certain that this is a riverbank landslide. Unfortunately the Google Earth imagery for this location does not have a high resolution, but Ambunti appears to be on the outside of a sharp river bend, and there is a feature sticking into the river on the apex of the bend that looks suspiciously like an old landslide, but that is pure speculation at this stage:
22 July 2015
News 24 has posted the following video on Youtube in the last 24 hours. It was apparently shot in Chamoli District of Uttarakand in northern India, but I have no further information. It is a spectacular failure, as the screen shot below shows:-
I recommend fast forwarding to about 18 seconds to see the event properly:
Meanwhile heavy rains also appear to be causing problems in other parts of the mountains of Central and South Asia:
- In Chitral, northern Pakistan, reports suggest that 300,000 families have been displaced by flash floods. It is likely that many of these events will be debris flows.
- In Tajikistan, mudslides killed seven people in Vanch district of Gorno-Badakhshan.
- There are signs that the heavily remediated Varunavat Parvat landslide in Utterkashi, northern India, has reactivated.
- In Chechnya a minibus fell from a road near to the village of Kharachoy in Vedensky District , killing at least seven and possibly eleven people, and injuring a further six. Reports suggest that the vehicle was struck by a rockfall or landslide.
But on the brighter side, the impact of landslides in the earthquake affected areas of Nepal has been lower than feared, primarily because so far the rainfall has not been excessive to date. There is still a long way to go in the 2015 monsoon though, and the real danger is from cloud burst events that can occur at any time.
21 July 2015
A huge portion of the northern part of the island has been mined out. This is a mine that appears to be very prone to landslides – the image below shows an earlier collapse for example:
There is an excellent gallery of images of the landslide last week on the ABS CBN website, from which this image is taken:
The ABS CBN report suggests that this is a very large landslide – 374,000 cubic metres. The failure appears to be a rotational slip with quite a high level of mobility at the toe. The report also indicates that the slope was being monitored with prisms (i.e. optical surveying), so it is quite surprising that such high levels of loss occurred. I would be very interested to see the data.
Anyway, there is a video version of the news report on the Youtube website. This includes a section of video that I have not seen before – it starts about 20 seconds into the report – that shows an earlier (smaller) landslide in the same mine:
This is quite interesting in terms of the way that it starts as a comparatively small cliff collapse but then fragments on impact to transition into a high mobility flow. It is understandable that the effects are so dramatic when people get in the way of these landslides.
20 July 2015
The torrential rainfall of 30th June / 1st July in Darjeeling, northern India triggered large numbers of landslides, causing a substantial number of deaths. The Save the Hills blog has set out to document the landslides in the Kalimpong area, an exceptionally useful achievement. I don’t intend to reproduce their report here, but will highlight a few aspects. First, they have produced a map of the landslides, and are willing to make the coordinates of them available:
This is landslide number 1, which killed two people:
These are other major landslides in Kalimpong:
There are many more images on the Save the Hills website. I continue to share the view with Save the Hills that many of the landslides could be avoided with simple good management of the slopes. There is much to learn from elsewhere – this increase in losses from landslides in Darjeeling is both unnecessary and avoidable.
17 July 2015
Marzia Colonna is an Italian artist who is based in Dorset in southern England. Educated in The Accademia di Belle Arti and at Morley College, she now works in collae and scuplture. Marzia Colonna has an upcoming exhibition at the Sladers Yard Gallery in West Bay in Dorset. One of the pieces that will be in the exhibition is a collage entitled “Rockfall at Burton Bradstock”:-
This is a beautiful piece that captures both the majesty and the danger of these cliffs. In July 2012 a rockfall from these cliffs killed 22-year-old Charlotte Blackman from Derbyshire – this is the BGS image of the location, compiled using a terrestrial laser scan and orthorectified digital photograph:
The depiction in the collage of the variable properties of the cliff face, and in particular the colour changes associated with contrasts in the degree of weathering between fresh rockfall scars and older sections of cliff, is particularly impressive.
Part 22 of the Landslides in Art series can be found here
16 July 2015
Landslides on Pluto?
Overnight a series of stunning images of the surface of Pluto have been sent back to Earth by the NASA New Horizons spacecraft. These images are so good that they have even made the first story on the BBC News website – quite remarkable given the importance of the Greek debt crisis. The discovery that Pluto is geologically active seems astonishing, not least because a mechanism to drive active geological processes is not apparent.
The presence of mountains on the surface of the planet, and the absence of impact craters, suggests some form of active uplift process. On Planet Earth, active uplift is always accompanied by some level of active erosion, and in the presence of water this denudation is usually accomplished primarily by landslides. In extremely arid environments, erosion may be driven by seismically-induced landslides, as we explored in our recent paper on the 2010 Mexico earthquake (Barlow et al 2014). So a fascinating question is whether the creation of young mountains on Pluto also means that landslides (in this case ice avalanches presumably) are present too.
The image below has been generated by NASA, showing mountains rising 3500 m above the base surface near to Pluto’s equator. These mountains are thought to be formed from ice and are less than 100 million years old. Note the scale of the image, 50 miles is about 80 km:
Although I am no planetary scientist, on first inspection there are features on the surface that are reminiscent of active slope processes. This is an enlargement of the image in which I have annotated some key features:-
I am speculating here as to the nature of the features, but on many of the slopes there are streaks that look like landslide tracks, and there also appears to be debris at the slope toes in many places. In the mountain on the “north” side of the image there is a feature that could well be a landslide track with a displaced mass at the toe – this has many of the features of a terrestrial landslide, although of course this would be a very large body. Finally, and pushing the boundaries of speculation to an extreme, in the “southeast” portion of the image there is a mountain with a huge arcuate face and what appears to be debris at the toe. Could this be a giant mountain collapse landslide? If so it will be of enormous volume.
I am sure that the NASA scientists will be looking at these images in detail in the months ahead, and will be able to come to a much better conclusion about whether Pluto has landslides. But I will be surprised if it does not.
Barlow, J., Barisin, I., Rosser, N., Petley, D., Densmore, A. and Wright, T. 2014. Seismically-induced mass movements and volumetric fluxes resulting from the 2010 Mw = 7.2 earthquake in the Sierra Cucapah, Mexico, Geomorphology, Available online 24 November 2014, http://dx.doi.org/10.1016/j.geomorph.2014.11.012.