20 April 2019
Taroko Gorge: a dashcam video of a very near-miss with a co-seismic rockfall in Taiwan
A magnitude 6.1 earthquake struck eastern Taiwan on Thursday 18th April 2019 at at 13:01 local time. This shallow earthquake shook the extraordinarily beautiful Taroko Gorge in eastern Taiwan, a major tourist attraction with very tall, very steep slopes above a major highway. A dashcam video has been posted to Youtube, shot by a motorist on the road at the time of the earthquake. Unsurprisingly, the earthquake triggered large numbers of rockfalls. The dashcam video captures a near-miss event that was extraordinarily close to being a tragedy:-
The video hits the road just in front of the car, and then fragments and bounces, with the debris flying over the top of the vehicle. Note that further rockfalls also occur:-
“In the video, a couple is casually driving on a sunny day through the Luoshao Road Section of Provincial Highway 8 in Taroko National Park. When the car reaches approximately the 153 to 161-kilometer mark, the driver feels the road start to shake, and in a twist of fate, he decides to pull over briefly, possibly buying precious seconds that saved his life.”
The video has a date and time stamp in the footer that suggest that it is genuine.
Elsewhere, two hikers were struck by falling rocks in Taroko Gorge. One of these individuals, a Malaysian national, suffered serious injuries. There is also a nice video of an earthquake-triggered rockfall elsewhere in eastern Taiwan, in this case at Qingshui Cliffs:-
It is likely that similar events have occurred on the steep slopes in Hualien County, but I have seen no reports of large landslides to date.
18 April 2019
A dramatic debris flow video
This video has been posted to Youtube, but with no explanation:-
It shows a debris flow cascading over a cliff above a mountain road, with a trapped 4×4. It appears that the part of the event captured by the video probably follows the initial major surge, which appears to have deposited a large volume on the road:-
Does anyone know anything more?
Parts of the Himalayas are suffering from unusual levels of pre-monsoon rainfall, with substantial losses from landslides and floods. For example, the Jammu-Srinigar highway has been blocked repeatedly over the last few weeks, and there have been several fatal landslides in Pakistan this year already. In the case of Pakistan, this rainfall has been sufficiently unusual to justify a dedicated Wikipedia page. An editorial in Pakistan Today questions why hazards driven by climate change are not given a higher priority in that country:-
“The weather predictions by the Pakistan Meteorological Department and the warnings to the population by the Pakistan Disaster Management Authority provide insufficient time to the population to fend for itself. The concerned agencies, that include police, Rescue 1122 and provincial disaster management authorities, are under-staffed, ill-equipped, and mostly urban-specific. The way climate change is hitting Pakistan, any extreme climate event can lead to a disaster. There is a need to strengthen the forecast and rescue bodies now rather than wring hands and blame the past governments when the tragedy occurs.”
To date, 2019 has seen an unusual level of landsliding worldwide, with fatalities totaling over 1,000 already, even though the first three months of the year are usually the least active period. Significant losses have occurred in rainfall induced events in Africa, South America, SE. Asia and in East Asia, as well as in mining and construction induced landslides.
16 April 2019
Planet Labs Skysat image of the Hindalco tailings failure
Planet Labs have successfully acquired a high resolution SkySat image of the Hindalco Tailings failure in Muri, India, which occurred last week. It is interesting to compare this with the pre-failure imagery. This is a Google Earth image of the site, collected on 4th April 2018 – i.e. almost exactly one year before the collapse:-
In comparison, this is the Planet Labs Skysat image of the site after the collapse:-
Whilst this is a more detailed view of the area that failed:-
The failure appears to have occurred in the retaining structure on the west side, allowing tailings to move to the west and to a lesser degree to the south. Note the large rear scarp of the landslide. In this case the mobility of the tailings has been quite limited, presumably because they are comparatively dry?
A key task will now be to contain the waste prior to the monsoon to prevent larger-scale contamination of the area. At the moment the affected area is quite limited.
Meanwhile, the Jharkhand State Pollution Control Board has cancelled the consent to operate of the works at Hindalco. Interestingly, there also reports that the retaining wall was designed by IIT Mumbai and IIT Roorkee, who are now under investigation. A panel has been convened to understand the causes of the failure.
Reference and acknowledgement
Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA.
Thanks to Robert Simmon for help in acquiring the Skysat image.
15 April 2019
Flüela Wisshorn: a large rockslide in the Alps on 18th March 2019
On 18th March 2019, late in the night, a large rockslide occurred at Flüela Wisshorn in the Swiss Alps. The best image of the landslide can be found in a good, detailed article about the event on the Tages Anzeiger website (the article is in German, but Google Translate does a good job):-
This rockslide has been investigated by the WSL Institute for Snow and Avalanche Research (SLF), and some of their initial findings are described in the article in Tages Anzeiger. The Flüela Wisshorn rockslide occurred shortly after midnight, meaning that there were no people at risk, with a volume of about 250,000 cubic metres. Images from the site suggest a failure on an existing defect in the rock mass; interestingly the rockslide scar extends to the ridge:-
Whilst most of the debris has had a comparatively limited runout (and it is interesting to see how much material remains on the steeper parts of the slope), a portion of the landslide has traveled a significant distance. This image, via Deutscher Alpenverein, is a rather beautiful illustration of that:-
The article in Deutscher Alpenverein notes that lowest part of the track seems to have the characteristics of a snow avalanche (with some debris content), rather than a rockslide. The timing of the rockslide is quite interesting, occurring in the latter part of winter and at night. I have no doubt that SLF will investigate this event further, and will be interested to read their conclusions on triggering in due course.
Thanks to Axel Volkwein for highlighting this event.
13 April 2019
Hindalco, Muri: another tailings failure, this time in India
On 9th April 2019 yet another significant tailings failure occurred, this time at the Hindalco works at Muri in Jharkhand, India. The location is 23.364, 85.871.
There are some limited reports of this failure event in the media. For example, the Daily Pioneer has a reasonably detailed report:-
“On Tuesday afternoon, boundary wall of the caustic pond created by Hindalco Ltd to dispose of red mud recovered in the process of extracting aluminum collapsed thus leading to a landslide like situation in Muri near the railway tracks.
“As an impact of the boundary breach, a few dumpers, earth movers and tractors which were parked in the area were buried in the mudslide.”
There are very few images of this event in the media. The best idea of what happened can be gained from a Youtube video posted by R M Kumar:-
This includes the following still:-
Meanwhile Bhaskar.com has this image:-
Both images appear to show significant failures through gabian walls. To me, to support a tailings pile on this scale with gabian structures is something of a surprise. An inquiry has been ordered; it will be interesting to see what it shows.
Planet Labs have captured the aftermath of the tailings failure via their Planetscope satellites. This is an image of the area before the failure:
Whilst this is the aftermath:-
The images suggest that this is a significant failure. Astonishingly, it is not clear as to whether there has been loss of life. Some reports suggest up to 20 people may have been killed, but most reports suggest a rather lower human impact. Meanwhile, operations at the plant have been suspended.
Reference and acknowledgement
Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com
Thanks to a friend in India who highlighted this event to me.
10 April 2019
GEER report on the Palu-Donggala landslides
The GEER team that travelled to examine the Palu-Donggala landslides, triggered by the 28 September 2018 Mw=7.5 Palu earthquake in Indonesia, have now published and made available their report (Mason et al. 2019). This is, as far as I am aware, one of the first detailed published reviews of these intriguing but terrible flowslides.
The report is detailed and well-curated, providing insight through both field observation and eye-witness reports. There is far too much to cover in a single post, so I will highlight what I consider to be the key take-home messages:
1. The report confirms that there were four major flowslides triggered by the earthquake (the team also surveyed a smaller landslide in the same area), inflicting huge losses on the communities in the local area. These are shown in the image, from Mason et al. (2019), below:
2. The team estimate that 80% of the 4340 fatalities caused by the earthquake were the result of these four flowslides, confirming that this is the worst landslide disaster in the last five years.
3. The team note that the landslides occurred on very low angled slopes. Typically these were in the range of 2 to 4% grade.
4. Field observations confirm that these landslides were the result of extensive liquefaction, triggered by the earthquake shaking. The team observed sand boils at the landslide sites, and in the surrounding areas, which is a diagnostic feature of liquefaction processes.
5. But interestingly, and importantly, the team conclude that thee of the four landslides were associated with unlined canals located in the headscarp areas. As the team pit it in the summary of the report.
“An unlined irrigation canal forms the upper boundary or crest of slides that occurred on the eastern side of the Palu basin. The canal contributed to saturation of the ground (typically used as agricultural fields and rice paddies) at these locations, where the groundwater table would otherwise be at greater depths. The canal was breached by the landslides at several locations and contributed water to later stage mudflows at some locations. Thus, the canal is believed to have played a critical role in the initiation and progression of the landslides on the east side of Palu basin.”
This collage of images, from the report, shows the damage to the canal, and some of the downslope deformation, from the Petobo landslide:
This is an incredibly useful and interesting initial report. Detailed analysis is needed of each of these four major landslides, but the role of the irrigation canal in the initiation of the landslides has important implications elsewhere.
Mason et al. 2019. Geotechnical Reconnaissance: The 28 September 2018 M7.5 Palu-Donggala, Indonesia Earthquake. GEER-061. doi:10.18118/G63376
9 April 2019
Eco-Safe Roads – resources to guide construction
Following my recent post on the need for properly engineered roads in high mountain areas, such as Nepal, Karen Sudmeier contacted me to highlight the work that she and her colleagues have undertaken on eco-safe roads. This work is featured in a piece on the IUCN website, featuring the use of bioengineering for improving slope stability along mountain roads. Bioengineering is not new, and can be highly effective, but its use remains disappointingly patchy.
The most useful element of this work is a manual that they have produced entitled “Community-based bio-engineering for eco-safe roadsides in Nepal”, which aims to provide “guidance to communities and local government agencies on the occurrence, assessment and mitigation of road construction-induced landslides and erosion.” The guide can be downloaded as a PDF.
This is a genuinely fantastic document, free of technical jargon, that both identifies the issues and offers really positive guidance on how to manage them. The first part of the document describes, with diagrams, the types of hazards that might be encountered. For example, this is the section that explains the hazards associated with earthflows:-
The guidelines then provide a very helpful classification tool for measures to be considered:-
Each of the techniques are then described in detail, including guidance on how to do it, the requirements, the advantages, the functions and the disadvantages / limitations.
I think this is a very helpful, very pragmatic set of guidelines that, if implemented, could make a huge difference. The guidelines can also be adapted easily for other locations / territories, in particular through the use of local plant species. They deserve wider recognition.
Devkota, S., Sudmeier-Rieux, K., Penna, I., Eberle, S., Jaboyedoff, M., Adhikari, A. and R. Khanal (2014) Community-based bio-engineering for eco-safe roadsides in Nepal. Lausanne : University of Lausanne, International Union for Conservation of Nature, Nepal and Department of Soil Conservation and Watershed Management, Government of Nepal.
3 April 2019
The complexity of the timing of rockfalls
A decade ago the research team that I led at the University of Durham undertook a study of rockfall activity on the North Yorkshire coast in the UK (see for example Rosser et al. 2015). In this work we used terrestrial laser scanning on a monthly cycle to detect rockfall locations on high coastal cliffs. The work was fascinating, arduous and intriguing. We found huge numbers of rockfall events, but given the comparatively long intervals between the scans we really struggled to understand the controls on the temporal occurrence of the rockfall events.
A paper just published in the journal Geomorphology (Matsuoka 2019) describes high resolution monitoring of a natural rock slope high in the southern Japanese Alps, with the intention of understanding these controls. This is a fabulously thorough piece of work, using a remote camera, debris traps, rock temperature, rock moisture and automated weather stations that collected records of air temperature, wind, precipitation and suchlike. The quality of the data yielded by this study is superb – for example, this is the annual record of rockwall retreat, rock temperature, rock moisture, air temperature and precipitation:.
For reference, this is a Google Earth image of the slope that was monitored, on the Aresawa headwall on the southeast side of Mount Ainodake:-
The top graph shows the rate of erosion (retreat) of the rock slope as rockfalls have occurred. This was determined by capturing sediment in traps at the foot of the slope. If the rock face area is known, then the sediment volume provides an average rate of retreat over the entire surface over the time period between the measuring period. In reality, the rate of retreat for any given point will vary considerably, controlled by the timing of specific rockfall events.
It is perhaps unsurprising that the data is complex. But Matsuoka (2019) found that there were five key processes that control the generation of rockfall events:-
- Inevitably, heavy rainfall events triggered significant rockfalls. These rainfall events occurred in the summer and early autumn;
- Lighter rainfall events led to increased moisture levels in the rock face. If this was followed by cold conditions that induced shallow freezing, rockfalls were observed when rapid thawing followed. These events occurred in spring and autumn;
- Similar events to (2.) occurred in colder periods, when the precipitation fell as snow;
- Thaw after deep winter freezing enabled the release of large rock blocks;
- Small rockfalls were enabled by short duration cycles of freeze and thaw, especially in the winter months.
It is interesting that wind did not appear to be a key control. This work emphasises the complexity of rockfall generation. Similar complex behaviour is undoubtedly seen in other settings, such as coastal cliffs, in each case controlled by the prevailing weather conditions. It is the advent of these very high resolution data capture techniques, and the ability to analyse very large, very complex datasets, that is now providing the capability to decode these process properly.
Rosser, N.J., Petley, D.N., Lim, M., Dunning, S.A., and Allison, R.J. 2005. Terrestrial laser scanning for monitoring the process of hard rock coastal cliff erosion. Quarterly Journal of Engineering Geology and Hydrogeology, 38 (4), 363-376.
2 April 2019
Tsangpo gorge: a first analysis of landslides triggered by the 2017 Ms=6.9 Milin earthquake
On 18th November 2017 a shallow Ms=6.9 earthquake struck the Tsangpo Gorge area of Tibet. At the time I used satellite imagery from Planet Labs to show that the earthquake had triggered large numbers of landslides along the Tsangpo Gorge. Some of these were valley blocking, although fortunately the blockages proved to be short-lived. A paper (Hu et al. 2019) in the journal Landslides provides an analysis of the landslides triggered by the earthquake, based on mapping from satellite imagery.
In total, Hu et al. (2019) mapped 766 coseismic landslides, with a total volume of about 31 million cubic metres. Whilst this number seems small, the authors note that mapping with satellite imagery means that many of the smallest landslides will not be identified.
The authors have included the image below in the paper showing the landslides triggered by the earthquake. It is clear that there are clustered around the walls of the Tsangpo Gorge:-
Interestingly, Hu et al. (2019) note that the landslide distribution was dominated by the presence of the deeply-incised, V-shaped gorge rather than proximity to the fault (which is the case elsewhere). Thus, in this case, topography has been the controlling factor in landslide development.
In total, nine valley-blocking landslides developed in the earthquake, although only three lakes formed within the Tsangpo Gorge. These breached within a few days.
The authors highlight the increased likelihood of debris flows in this area in the aftermath of the eaethquake, in common with effects seen elsewhere. Interestingly, they also highlight increased risk of glacial debris flow events in the area. On 17th October 2018 such an event occurred downstream from the earthquake-affected area at Sedongpu. This event, which blocked the Tsangpo to a depth of 80 metres, had a volume of about 33 million cubic metres according to Hu et al. (2019). Ten days later a further glacial debris flow occurred at the same site.
Hu, K., Zhang, X., You, Y. et al. 2019. Landslides and dammed lakes triggered by the 2017 Ms6.9 Milin earthquake in the Tsangpo gorge. Landslides. https://doi.org/10.1007/s10346-019-01168-w
1 April 2019
Mountain roads in Nepal
One of the major foci in the development of Nepal, as in many poor mountainous countries, has been the construction of mountain roads. The aims are laudable – by providing wheeled connectivity, the roads aim to provide “quicker transportation of goods and better access to employment, education, health care and markets”. But the impacts of roads are complex, with strong evidence that they drive migration and trigger major social changes in the newly connected communities. Not all of these changes are positive.
Whilst I recognise the importance of mountain roads, I have long expressed concerns about the environmental degradation that they cause, using Nepal as a case study. A commentary (Sudmeier-Rieux et al. 2019) has been published in Natural Hazards and Earth System Sciences, which is open access, which examines the issues with mountain road construction in Nepal. The context is the likely convergence between the Chinese Government Belt and Road Initiative and the decentralised approach to development in Nepal, which together are likely to drive the construction of more mountain roads.
Sudmeier-Rieux et al. (2019) note the extraordinary development of roads in Nepal in recent years. In 20 years the local road network (for the most part consisting of mountain roads with minimal engineering, often built by a small team with a bulldozer) has increased by 1200%. In 2011/12, they note that Nepal spent 8% of its national budget on road construction. But, as the authors note, Nepal’s mountain roads “are in a treacherous state, subject to frequent rockfall, landslides and accidents”. The roads lack drainage and slope support, often driving the destruction of irrigation schemes, burying springs and contaminating water supplies, leading to severe losses due to erosion.
The image below shows a typical mountain road in Nepal, illustrating the problem:-
It is easy to find examples of these impacts of mountain road construction in the Hill Districts of Nepal:-
The authors make a strong argument that the problem is political not technical. The engineering techniques exist to make these mountain roads sustainable. Sudmeier-Rieux et al. (2019) argue that the major problems with these poorly constructed mountain roads can be managed if “government policies were enforced to achieve well-established road engineering designs, including basic standards of road grading, alignment, drainage and bioengineering”. They argue that the move to decentralisation of power in Nepal, and the influence of the Belt and Road Initiative, provides the mechanisms to exert this control.
It is hard to disagree. Sadly, I have little confidence that it will happen, and I fear that we will now see a new wave of road construction driving increased landsliding in Nepal, with high levels of loss and more environmental damage.