25 June 2016
Galway peat bog landslide
Various news agencies in Ireland are reporting a peat bog landslide at Clifden in Galway on Thursday night. Reports suggest that 4000 tonnes of material have shifted, blocking the N59 Connemara to Galway city road. Reports suggest that the slope was still moving on Friday.
Peat bog landslides are quite unusual (not least because peat bogs are quite rare), and behave in a manner that is also a little different. This is because the main mass of the landslide is saturated organic material that has a low density. This makes them unusually mobile once they are disturbed. I blogged about a set of peat bog landslides in Ireland back in 2009.
The best view of this peat bog landslide comes from a Youtube video of drone footage:
Notice the very disturbed area at the crown of the landslide, which is typical of a peat bog landslide. The mobility of the slide is clear as the mass has moved on an unusually low angled slope.
This is the full video of the landslide:
Details about the Galway peat bog landslide
The location of the landslide appears to be at 54.4778, -9.8981 (54.4778 N, 9.8981 W). There is good imagery of the site on Google Earth, taken in 2011:
Peat bog landslides are usually associated with heavy rain, as appears to be the case here. Sometimes disturbance of the slope by human activities also plays a key role, but there is nothing to indicate that was the case here. Of course peat bogs take hundreds of years to form, so these events have a long legacy. As peat is also an important store of carbon, it should be actively preserved where possible. Sadly, the rapidly increasing rainfall intensities that are being seen in many places as a result of climate change means that these sorts of events are likely to become more common.
22 June 2016
Pingle County quarry collapse
Xinhua reported on Monday that a quarry collapse had trapped seven people in Pingle county, Guangxi Zhuang Autonomous Region in China. They provided little detail other than to say that rescue operations were ongoing. However, CCTV has now posted a very high quality video of the site, and of the rescue operations, on Youtube:
Based on the images this looks to be a classic rockslope failure caused by undercutting during the quarrying. This is a still from the video:
I think that on the upper part of the scar the detachment may well be controlled by two large joints. This would explain the very hefty boulders in the rockfall deposit. Note also the very clear horizontal discontinuity running across the lower slope. The rockslope collapse has generated a deposit that is exceptionally coarse-grained:
The ongoing rockfall activity, and the potentially unstable nature of the remaining rock mass, means that the rescue operations are extremely hazardous. Sadly I can think of no examples in which people have been successfully rescued from beneath a deposit of this type. I suspect there may be cases, but they are rare, and they will always require that the survivor was sheltered in some sort of structure.
Once again the desperate need for improved quarry and mining safety in China has been highlighted. The toll from quarry landslides there remains fearsome.
Heavy rains across southern China
Meanwhile, Xinhua is also reporting the terrible toll from the heavy rains that are currently affecting the southern part of China. Floods and landslides are reported to have killed 22 people to date, with another 20 missing. This includes a substantial landslide in a railway construction site in Sichuan Province:
In Xingwen County, southwest China’s Sichuan province, five more bodies were found at a railway construction site, bringing the death toll from landslides in the county to seven. Following heavy rain, a landslide occurred around 3 a.m. Sunday that destroyed workers’ dormitories. Three people were hospitalized, they remain under observation but are in a stable condition.
21 June 2016
Kumamoto earthquake: post-seismic landslides
One of the most serious concerns about the Kumamoto earthquake in Japan was that the timing, shortly before the rainy season, meant that there was high potential for post-seismic landslides. These have frequently proven to be problematic – in essence the first exceptional rainfall after the earthquake tends to drive a spike in landslide activity, with potentially disastrous effects. In the Kumamoto earthquake large numbers of slopes were left in a fragile state. Yesterday, heavy rainfall across the prefecture triggered extensive landslides and flooding. The Asahi Shimbun has a summary of known losses so far:
- In Kamiamakusa a 92-year-old man was killed in his house by a landslide.
- In Uto two houses were buried, leaving one man dead and a woman missing.
- In Kumamoto city two people were trapped by a landslide in their home. One has been confirmed dead, the other is missing
There was also a flood-related death – a 79-year-old man who fell into a drainage ditch and drowned in Kosa.
The Japan Meteorological Agency provides a real time landslide risk map. This is how it looked yesterday (via Robert Speta and Twitter):-
And again this morning (direct from the Japan Meteorological Agency website):-
Rainfall will have been very variable across the region, but in Kumamoto itself the impact seems to have been a short burst of extremely intense rainfall – 89 mm fell in a single hour. Sadly this occurred late in the evening, when people are least likely to be able to see or even hear a landslide coming. Kosa, mentioned above, is even worse:-
In this case the maximum hourly precipitation was a staggering 123.5 mm. Again the most intense rainfall arrived in a short duration, very high intensity burst with devastating consequences. This is one of the landslides in Uto:
20 June 2016
Central Java: disastrous landslides in Indonesia over the weekend
Heavy rainfall in Central Java, Indonesia triggered landslides and floods over the weekend, with disastrous consequences. The headline seems to be 46 confirmed fatalities with a further 27 people reported to be missing, although this is not entirely clear at the moment. I have been trying to glean information from various news reports:
- The Jakarta Globe reports 29 people were killed in Purworejo, all by landslides, with a further 11 still missing.
- The Jakarta Globe also reports 17 people killed in Banjarnegar, with a further 6 missing.
In terms of specific landslide incidents:
- On Saturday a landslide at Sampang Village (also reported as Dukuh Pohkumban) in Sempor district, Kebumen reportedly buried three houses, killing six people
- In Karangrejo, Caok nine people were killed according to Anshora
- Also on Saturday nine people were killed at Gumelem by a landslide on a road. Reports suggest that the victims were clearing the debris from one landslide when they were struck by another.
- A landslide reported as occurring at Donorati reportedly killed 11 people.
- A landslide at Sidomulyo Village in Purworejo reportedly killed five people
- In Mranti two people were reportedly killed
- In Jelok village in Kaligesing a landslide killed three people
- And in a landslide in Bagelan (also reported as Parry, Berjan) one person reportedly died.
The total from the above is 46 people, which tallies with the headline above, although I suspect that this might be more luck than judgement. If anyone can provide better information then I would appreciate it.
There are a few images of the landslides on the internet. This one, from Purworejo, suggests that some of the landslides have been quite large:
Whilst this one was posted on Twitter:
Hopefully more information will appear over the next few days.
18 June 2016
Using climbing guides to examine changes in rockfall activity in the European Alps
One of the anticipated, and increasingly observed, effects of anthropogenic climate change is the degradation of permafrost in high mountain areas. A key role of permafrost is in holding fractured rock masses together. As the ice melts, the strength of the rock mass rapidly declines, and rockfalls result. Given that some mountain areas, such as the European Alps, have already shown 2 degrees Centigrade of warming, these effects are already with us, and are getting worse. But of course it can be hard to assess the level of rockfall activity prior to the modern instrumental age. As this was not a parameter that was being monitored until recently, understanding of this problem in a historical context is hard.
In a recent paper in the journal Geografiska Annaler, the climber and geomorphologist Arnaud Temme has examined warnings of rockfall activity in Alpine climbing guides over a 146 year period in the Bernese Alps of Switzerland. This is an area that has been extensively climbed for well over a century, with a regular flow of climbing guides through this period. Some of these guides are one-off descriptions by the authors, whilst in others the same author has provided repeated updates. Temme (2015) describes this as an early form of crowd-sourcing of rockfall activity. Of course a substantial advantage here is that climbers have to be very aware of rockfall danger, and the authors are often acute observers of the behaviour of the rock mass. Whilst this is not a real substitute for quantitative data, it does provide very interesting insight into the effects of climate change in high mountains.
The study focuses on 17 Swiss Alpine Club guidebooks dating from 1864. The first four were written by the same English author (Bell), whilst later versions had more local authors. The analysis in the paper is sophisticated because of the need to take into consideration changes in the number of routes described and changes in societal views of risk, as well as changes in authorship. But, allowing for these factors, the results are clear. There has been a strong increase in the reported occurrence of rockfall danger. Temme (2015) presents this graphically:
It is clear that there has been a remarkable increase in the description of rockfall danger over the period, and that most of this has occurred in the last three decades. Whilst an aspect of this could be a increased sensitivity to risk. Temme (2015) is clear that the major factor is increased rockfall activity. In the analysis he also looked at the correlation of this increased rockfall risk with various physical factors, and found that there was a strong relationship with slope aspect. This is consistent with increased rockfall activity occurring on slopes with an eastern or western aspect, where the freeze-thaw effect is known to be strongest.
This is another study that shows elegantly that anthropogenic climate change is having a strong effect on landslide activity. Of course there is an opportunity to continue this study in other intensively-climbed areas of the European Alps, and to use climbers as a crowd-sourced provider of rockfall data.
Temme, A.J.A.M., 2015. Using climber’s guidebooks to assess rock fall patterns over large spatial and decadal temporal scales: an example from the Swiss Alps. Geografiska Annaler: Series A, Physical Geography. 97, 793–807. doi:10.1111/geoa.12116
17 June 2016
Review of a paper: fatal landslides in Europe
In a paper just published in the journal Landslides, Haque et al (2016) present an analysis of fatal landslides in Europe between 1995 and 2014. This is an interesting piece of work that sits nicely alongside the work that I have published on worldwide landslide losses Petley (2012) and in Latin America (Sepulveda and Petley 2015). In this period the authors have recorded a total of 476 landslides causing losses of 1370 people, with a further 784 injuries. The paper deserves careful reading as it contians a great deal of information, of which I will pick out just two elements.
First, the paper includes a map of landslide losses over this period, organised by 5 year blocks:
As expected, the spatial distribution of fatal landslides is very heterogeneous, with a higher concentration in Iceland, the Alps, the Apennines of Italy and in Turkey. France has surprisingly few, Spain a fairly even scattering. Much of the rest of the Europe has a small number. The location of the landslides of course reflects the distribution of mountain areas, and in particular those with seismicity. This is consistent with my earlier studies.
Second, perhaps the most surprising element of this study though is the data on the trend in landslide occurrence with time. This is the graph presented in the paper:-
The trend is clearly upwards over time, sharply so in terms of the number of landslides from about 2009 onwards, with a significant increase in losses as well. This was not clear in my global data, and we did not see this trend in Latin America either, so this is a very interesting result. Haque et al. (2016) suggest that the increase is primarily the result of large numbers of fatal landslides in Italy and Turkey (see the red triangles on the map above) and in the Balkan countries. The cause of this change is not clear, but the authors note that most of these landslides occurred in mountain regions with a humid temperate climate. This hints at a possible role of climate change.
Overall this is a very valuable study that is extremely welcome. It would be good to see a similar study for East Asia and for South Asia now as well. I hope that this database will be maintained.
Haque, U. et al. 2016. Fatal landslides in Europe. Landslide. Doi: 10.1007/s10346-016-0689-3
Sepúlveda, S.A. and Petley, D.N. 2015. Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean. Natural Hazards and Earth System Sciences, 15, 1821-1833, doi: 10.5194/nhess-15-1821-2015.
Petley, D.N. 2012. Global patterns of loss of life from landslides. Geology 40 (10), 927-930.
16 June 2016
Landslide video: a massive landslide takes out a truck in Peru
I know nothing about the circumstances of this video, which was reportedly shot on a mountain road in Peru, or how it worked out for the driver of the truck. Sadly, I suspect not well:-
This is a truly massive landslide, but the initial impact on the vehicle was to push it forward rather than burying it:
The video was posted on 11th June, but I have seen no reports about this event. Can anyone provide any more information?
15 June 2016
The boulder that came to tea
The Croatian news website Dulist has a story this week about a boulder that came to tea in a house in Dubrovnik. The pictures are quite startling:-
According to a translation of the article, this landslide happened during heavy rainfall on Monday night. This block was part of a larger landslide on State Road D-8. The images suggest that this boulder bounced on the road before smashing through the broadside barrier:
And then bounced again in the garden of the house (note the huge divot in the grass), before trying to gain entry via the a bedroom window:-
This looks to be a classic case of a boulder that is rotating around its shortest axis, and so has gained a stable geometry as it travels down the hill. This situation creates the possibility of high velocities, large bounces and long travel distances.
I’d imagine that removing the boulder from the window is not going to be a trivial task
According to the Dulist article, the same house was struck by a boulder in 2012. The Google Translation of the article, which I have tidied up, says:
The Křečková house has already been hit by a big boulder, almost exactly four years ago, namely on 16 June 2012, when the rocks in the fall broke several trees, skipped the road, bounced off the railing of the road, glanced off the fence sound the driveway parking and travelled like a projectile through the roof of the house. Fortunately the roof structure was able to stop the rock.
All of this suggests that some work is needed quite urgently to assess the stability of the slope above the road. The article appears to suggest that there may be more unstable blocks.
13 June 2016
Three forthcoming landslide meetings of interest
I thought I would highlight three forthcoming landslide meetings:
1. GSA 2016 in Denver, Colorado
The 2016 GSA meeting will be held in Denver from 25th to 28th September 2016. There are three landslide sessions:
T21. Bridging the Gaps on Subaerial, Lacustrine, and Submarine Landslide Research
Lesli Wood, Lorena Moscardelli
Submarine landslides are never witnessed, but the aftermath is clear: destruction of seafloor infrastructure, disruption of biota, and tsunamigenic coastal threats. This session looks at researchers attempting to bridge between subaerial and submarine landslide processes.
T24. Landslide Hazards: Inventories, Hazard Maps, Risk Analysis, and Warning Systems (Posters)
William J. Burns, Stephen L. Slaughter, Matthew M. Crawford
This session is designed to highlight landslide hazards information especially as related to landslide inventories, hazard maps, risk analysis, and warning systems.
T25. Landslides, Debris Flow, and Rock Fall: Processes and Hazards
Rex L. Baum, Benjamin B. Mirus
This session will explore new insights about landslide processes and hazards. Contributions that address novel field and instrumental observations, analysis, and hazard assessments or that introduce tools and techniques applicable to any of these are especially welcome.
The abstract deadline is on 12th July. Details here.
2. Waiting for the End of the World: The Archaeology of Risk and its Perception in the Middle Ages
This meeting will be held in Oxford from 2nd to 4th December 2016. Details are as follows:
3. 2017 North American Symposium on Landslides
9 June 2016
The response of Californian earthflows to drought
A really interesting paper has just been published in Geophysical Research Letters examining the response of Californian earthflows to the ongoing, epic drought. This paper was led by Georgie Bennett, currently at the US Forest Service and Colorado State University, but who will be joining us here at the University of East Anglia in January 2017 as a full faculty member. California has been suffering a serious drought for many years now. In the paper, Bennett et al (2016) mapped 98 active earthflows in a 140 square kilometre area of the Eel River catchment in California. This is an area with multiple large, often deep earthflows that are an important part of the geomorphic system. I have taken one of the larger earthflows from Google Earth below:
The mapping was very detailed, undertaken using aerial photographs. The mapping focused not just on the boundaries of the landslides, but also on the displacement of trees located on the landslides, which allowed a calculation of the velocity of the landslides with time. This data was then compared with an index of drought, the commonly-used and widely accepted Palmer Drought Severity Index (PDSI), which has been used previously to show that the 2012-2015 drought in California is unprecedented.
The results are fascinating – I highlight here two key aspects. First, over the last 70 years or so the velocity of the earthflows has markedly decreased. This image shows the mean velocity, with error bars and the PDSI. It is notable that in recent years the PDSI has become exceptionally low, and the earthflows have responded by slowing down:
Bennett et al. (2016) also looked at the differential response of the Californian earthflows of different depths to the drought conditions. They found that the shallower (typically 5 – 15 m thick) landslides showed quite variable response to the drought conditions, with the majority slowing down but a few actually accelerating. However, all of those deeper than 15 metres decelerated. In some ways I find this a quite surprising result – I would have expected that the deep landslides would have been less susceptible to the climate than the shallow ones. The result is robust, but the cause is not clear and is intriguing. Bennett et al (2016) suggest that it could be that the shallow landslides respond to short term and local effects (vegetation change, a large storm) that might occur within a drought, whilst the deeper Californian earthflows are just responding to the climate forcing.
This is a really interesting study, showing very elegantly the ways in which the landslide system is responding to climate change. With greater changes to come in the years ahead as the global climate warms further, we will see many more responses of this type.
Bennett, G. L., Roering, J. J., Mackey, B. H., Handwerger, A. L., Schmidt, D. A. and Guillod, B. P. 2016. Historic drought puts the brakes on earthflows in Northern California. Geophysical Research Letters. Doi: http://dx.doi.org/10.1002/2016GL068378