27 April 2021
Great Whale River: a very large, low-angled landslide in Canada on 22 April 2021
On 22 April 2021 a very large landslide occurred on the Great Whale River, upstream from the upstream of the villages of Kuujjuaraapik and Whapmagoostui in Quebec, Canada. Nunatsiaq News has this dramatic image of the landslide:-
The landslide is located at 55.298, -77.638. It is clearly visible on the Planet Labs image taken on 23 April 2021:-
The slide is large – from the crown to the channel it is about 1.6 km, and from the crown to the toe it is about 4 km.
The landslide is not thought to pose a direct threat to the communities downstream, fortunately, although there is some risk to users of the river as break-up of the ice is now unpredictable.
The news reports describes this as having occurred in an area of clay. The form of the landslide suggests that it could be a quick clay / sensitive clay failure. CBC has a splendid video shot from a helicopter that flew the length of the landslide. This is a still from that video:-
The video suggests that the downstream deposit is highly liquid mud with rafts of trees. Note that many are still standing upright. This is indicative of a quick clay landslide. The landslide itself appears to be quite deep-seated, probably reflecting a thick clay deposit. This implies that the volume of the landslide on the Great Whale River is likely to be in the millions of cubic metres.
There is little information as to the likely trigger at this point, but large landslides often occur in the spring as melt occurs.
Planet Team (2021). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
26 April 2021
The 21 October 1993 Pantai Remis landslide in Malaysia: an upscaled video
Early in the days of this blog I posted about an extraordinary video of a landslide in Malaysia. Almost thirteen years on this video remains hard to beat. The recording in question shows the 21 October 1993 Pantai Remis landslide in Malaysia.
This was a very unusual failure that occurred in an open cast tin mine near to the coast. Mining operations ventured too close to the sea, eventually triggering a collapse of the quarry walls. Ultimately the sea flooded the mine, creating a new cove that is still visible on Google Earth.
The video captures the collapse sequence of the Pantai Remis landslide. The failures occurred as massive rotational slides that transition into highly mobile flows through liquefaction. The mine quarry flooded catastrophically and completely. But the drawback of this video was that the quality was poor.
However, Jaren Christopher Kelley has posted a new version of the video to Youtube. This has been upscaled from the original, greatly improving the quality. You should be able to see the video below:
The image below shows the first rotational failure at Pantai Remis in action:-
One of the extraordinary aspects of this video is that it is timestamped, which allows a reconstruction of the sequence of events.
This video remains hard to beat, and the new version makes it much more usable.
23 April 2021
The 13 October 2020 landslide in Phong Dien, Vietnam, triggered by an extraordinary rainfall event
On 13 October 2020 heavy rainfall triggered a rapid landslide at Phong Dien in Thua Thien Hue, Vietnam. I covered this event at the time – it was a double tragedy as the landslide killed 13 members of a rescue team en route to another landslide accident. A paper (Van Tien et al. 2021) has just been published in the journal Landslides that provides a description of this event.
The events started with a landslide at the construction site of the Rao Trang-3 hydropower plant on 12 October 2020. This landslide killed 17 people. A rescue team was dispatched to assist in the rescue and recovery operation. The team stopped for the night at a location that is described as Ranger Station-7, situated in Phong Dien, c.10 km from the Rao Trang-3 site.
Van Tien et al. (2021) describe an extraordinary amount of rainfall. At the nearby A Luoi rainfall station, a total of 2190.2 mm was recorded in the period 6-12 October 2020. The landslide at Ranger Station-7 occurred at midnight on 13 October. The landslide is located at 16.434°, 107.311°. The Google Earth image below, collected in February 2021, shows the aftermath of the landslide:-
Perhaps surprisingly, Van Tien et al. (2021) describe the initial failure, at the top of the slope, as being rotational:
The landslide was characterized as a rotational type with a visible sliding surface, head scarp, and flanks in the upper slope area. The landslide took place on an average slope of 21° with a poor vegetation cover. The lower slope is quite gentle, with an angle of 18°, while the slope angle of the upper part is 27°.
The landslide length was 546 m, with a volume of 81,500 m3.
The authors suggest that failure occurred initially in a block downslope of the final crown of the landslide – a section that they call Block I:-
About 5 minutes later Block II failed due to the loss of toe support. Van Tien et al. (2021) suggest that the landslide was highly mobile, moving at 29 m/sec. Only eight of the 21 people in the Ranger Station survived, all with injuries.
This extraordinary rainfall event triggered many other landslides in the Phong Dien area, as the image below shows. Some appear to have had quite high mobility:-
Van Tien, P., Trinh, P.T., Luong, L.H. et al. 2021. The October 13, 2020, deadly rapid landslide triggered by heavy rainfall in Phong Dien, Thua Thien Hue, Vietnam. Landslides. https://doi.org/10.1007/s10346-021-01663-z
20 April 2021
The 19 April 2021 coastal landslide at Nefyn Bay in North Wales
This landslide is interesting for its timing – the UK is having a spell of unusually dry weather for April – and for its runout, which is quite long.
This landslide has received some attention in the UK, but strangely the most interesting element has not really received much publicity. This is that the landslide was captured on video by a woman, Amanda Stubbs, who was standing at the toe. It is brilliant. You should be able to see it below:-
The landslide starts as a small retrogressive slump on the margin of what becomes the main slide. This destabilises the main mass, which fails through a strongly rotational mechanism. After failure the mass runs across the beach as a high mobility earthflow.
There is some excellent drone imagery of the aftermath:-
Tirlithriad Nefyn 19.04.2022 pic.twitter.com/oI7y0lA2Xb
— Cai Erith Williams (@caierith) April 19, 2021
The imagery shows the multiple scars of previous landslides on this section of coast, so this failure comes as no surprise. The British Geological Survey (BGS) have a page dedicated to coastal landslides at Nefyn Bay, based on work undertaken after a fatal landslide on this section of coast in 2001. There is also a paper online (Jenkins et al. 2007 – one of the authors is my former PhD student Andy Gibson) that describes the nature of the landslides at the site and the evolution of the hazard. The landslides occur in glacial deposits that are eroded by the sea, exacerbated by sand layers overlying a low permeability clay.
Jenkins, G.O.; Gibson, A.D.; Humpage, A.J.. 2007. Climate change and evolution of landslide hazard at Nefyn Bay, North Wales. In: McInnes, Robin, (ed.) Landslides and climate change: challenges and solutions. Proceedings of the International Conference on Landslides and Climate Change. Taylor and Francis, 113-119.
19 April 2021
Landslides from the 18 April 2021 M 5.9 earthquake near to Bandar Genaveh, Iran
On 18 April 2021 a M=5.9 earthquake struck the port city of Bandar Genaveh in Iran. The earthquake was centred on the town of Bandah Rig. There are some reports of damage in Bandah Genaveh, and five people were injured.
A couple of videos have been posted of landslides triggered by the earthquake. The best one is on Youtube:-
Inland from Bandah Genaveh there is a steep escarpment running sub-parallel to the coast:-
It appears that the landslides have been triggered from this escarpment.
The video is very dramatic, but for the most part these are likely to have been shallow slides of quite low volume. The very arid conditions means that such slides generate very large quantities of dust, which looks dramatic in the videos. Nonetheless, it is likely that coseismic landslides are an important part of the erosive processes in this area.
There are other videos of this event on Youtube. One of them presents a compendium of events, although I am not sure whether they are all from this earthquake. It includes a sequence that includes this still:-
The image above does appear to be the same event as that posted in the first video, but providing a much closer view of the landslides.
An analogy for this event is probably the 2010 M=7.2 Sierra Cucupah earthquake in Mexico, which also triggered landslides in an arid mountain chain. Led by my former post-doc John Barlow, we investigated the landslides from that event. There is a description in Barlow et al. (2014).
Reference and acknowledgement
Many thanks to loyal reader Andrew Noad, who kindly highlighted these videos to me.
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, 230, 138-145. http://dx.doi.org/10.1016/j.geomorph.2014.11.012.
15 April 2021
Changing rainfall patterns in the Indian monsoon with future warming
The global landslide hotspot lies is located in South Asia, driven by the summer (SW) monsoon. The monsoon drives a period of intense and prolonged rainfall in the period centred on June to September. Rainfall levels can be high – in some cases the highest in the world. The monsoon also drives convective activity that can cause cloudbursts. Together, these effects trigger large numbers of landslides, with catastrophic outcomes.
Thus, one of the key elements in the understanding of future landslide patterns is to understand the dynamics of the monsoon with climate change – i.e. under future warming. If the monsoon is likely to intensify then we might see more landslides through time. And of course vice versa. The pattern is not simple of course; the monsoon could weaken but rainfall intensity could increase. So understanding the dynamics of the monsoon is key.
A new open access paper has just been published in the journal Earth System Dynamics (Katzenberger et al. 2021) that examines the dynamics of the Indian monsoon under future warming scenarios. To do so it examines the 32 global climate models within the Coupled Model Intercomparison Project Phase 5 (CMIP5) under a range of emission scenarios.
The results are really interesting. As the authors put it:
All of these models show a substantial increase in June-to-September (JJAS) mean rainfall under unabated climate change (SSP5-8.5) and most do also for the other three Shared Socioeconomic Pathways analyzed (SSP1-2.6, SSP2-4.5, SSP3-7.0). Moreover, the simulation ensemble indicates a linear dependence of rainfall on global mean temperature with a high agreement between the models independent of the SSP if global warming is the dominant forcing of the monsoon dynamics as it is in the 21st century; the multi-model mean for JJAS projects an increase of 0.33 mm d−1 and 5.3 % per kelvin of global warming.
These are fascinating results. Under most likely scenarios for future warming the monsoon will strength, with more rainfall on average. In graphical form the figure below displays the outcomes:
Interestingly, the models project that both the west coast of India and the Himalaya region will show substantial increases in monsoon precipitation. These are the areas most affected by landslides. The models also suggest greater interannual variability, indicating that some years will be exceptionally wet.
Studies like this provide a general expectation for future behaviour. There will be nuances of course that require further investigation, such as the impacts on cloudburst rainfall and the interaction between the atmosphere and the topography. But in general terms, the models suggest that we might expect to see increased landslide activity driven by the summer monsoon with time. Coupled with the ongoing environmental degradation in the Himalayas, especially through haphazard road construction, the picture for future landslide impacts is poor. Strategies to adapt to future warming are urgently required.
14 April 2021
A lucky escape for a small dog, a Jack Russell Terrier, caught in a rockfall in North Yorkshire
The RNLI, the UK lifeboat service, has a great story about an exceptionally lucky escape for a small dog, a Jack Russell terrier. On Friday 9 April 2021 a man was reported missing on the coast near to Skinningrove on the North Yorkshire Coast. The man had been searching for his missing dog. Fortunately he was found and safely recovered by the RNLI.
The dog remained missing over the weekend. On Monday 12 April one of the RNLI volunteers, Ed Thomas, was walking his own dog close to where the man was found. He heard barking and discovered the missing dog buried beneath a rockfall. The dog was trapped by its rear legs:
Together with three other people, Ed was able to move the rocks to free the Jack Russell Terrier. The owners were contacted, the dog was checked out by a vet, and then taken home. The good news is that the dog was not seriously injured, and is now recovering.
The odds were stacked against this small dog. As I have noted previously, the survival rate for anyone caught in a landslide is very low. The size of the blocks in the image above demonstrates this clearly. The weather conditions over the weekend were not good, with temperatures below zero and even snow at times (quite unusual for the UK in April). There were strong winds at times, so conditions on the coast would have been brutal. This coast has a high tidal range, meaning that the chance of drowning was significant. And finally, the dog needed someone to hear a bark.
12 April 2021
The interesting morphology of the Culluchaca landslide in Peru
After posting yesterday about the Culluchaca landslide in Peru, I spent some time looking at the morphology of the site using the Google Earth Imagery. As a reminder, this is what the Google Earth images show. The image was collected in July 2019:-
The interesting features of this landslide lie above the crest of the slide shown above. The image below shows that area, on this occasion looking square onto the landslide:-
The image appears to show two arrays of tension cracks. The first set, marked with A, are about 50 metres back from the landslide crown. But there is another set, marked with B, that are probably less well developed. These are about 150 metres back from the landslide crown, indicating a very large instability.
Perhaps even more interesting is the set of features further across the slope. The image below shows the morphology of this area. I’ve left the other markers in place for reference:-
Running across the slope parallel to the crest is an array of linear depressions, some of which are large and extensive. Upslope from here is a ridge with extensive bouldery deposits, which is probably a scarp.
The most likely explanation for these features at that this is the site of a deep-seated gravitational deformation (DSGD), defined as “a gravity-induced process affecting large portions of slopes evolving over very long periods of time. A DGSD may displace rock volumes of up to hundreds of millions of cubic meters, with thicknesses of up to a few hundred meters.”
DSDGs are very large, slow creeping failures in rock masses, common in high mountain areas. I wrote about an example in Italy in 2019. They typically generate arrays of parallel scarps and troughs high up on the hillside.
Thus, the failure of the Culluchaca landslide on 7 April 2021 is probably only a small part of the unstable mass on this slope. However, that does not necessarily mean that further collapses are likely in the short term – DSGDs creep for hundreds and even thousands of years.
I should note that an alternative explanation for these features in this landscape as an active fault. This possibility cannot be precluded without further investigation.
11 April 2021
Culluchaca: a large landslide on 7 April 2021 in Peru
On 7 April 2021 a large failure occurred close to the village of Culluchaca in Huari province of the Áncash region of Peru. The landslide did not claim any lives but caused serious damage to about 1 km of National Road 14a:-
The location of the landslide appears to be -9.301534° -77.008174°. This is a Google Earth oblique view of the site:
The image shows an existing large failure at this site. Note also the very clear tension cracks located above the existing crest of the landslide. I suspect that a large block delineated by these cracks has failed. The image below shows the aftermath of the landslide:-
Note the very extensive scale of the landslide in the image above. It is clear that a large volume has failed.
According to a news report in Áncash Noticias (in Spanish), the population of the village of Culluchaca have had to be evacuated because of the risk. In addition the landslide has disrupted the electricity network supply the districts of Huacachi, Anra, Uco, Rapayán, Paucas and Huacchis in the province of Huari, and some parts of the province of Antonio Raimondi and Huamalies.
Clearly reinstatement of the road will be important, but this will not be possible until the landslide has stabilised again. It will not be a straightforward problem to solve. Fortunately the images above suggest that the river is probably not blocked by the landslide, at present at least.
9 April 2021
Oxley Highway: multiple landslides in New South Wales, Australia
The Oxley Highway is a rural road orientated east-west in New South Wales, Australia. To the west is the town of Nevertire, to the east it terminates at Port Macquarie on the Tasman Sea coast.
Heavy rainfall in March triggered multiple landslides along the Oxley Highway in a section between Yarras and Walcha. This is the landscape of the section in question:-
There is a good helicopter reconnaissance video showing the magnitude of the damage caused by landslides to the highway, posted to Youtube:-
The level of damage is also clear in some of the images released by Transport for NSW:-
There are more than 70 landslide sites along the road. Transport for NSW has estimated that it will at least two months before the road can reopen with a limited service, and several more months at least before the problems are fully mitigated. As the two images directly above show, some of the landslides are both large and located below the level of the road bench. Remediating these sites will be a substantial and expensive challenge.
Meanwhile, also in Australia, 7 Daily News tweeted a video yesterday of a coastal landslide in Queensland:
Another sinkhole has opened up at Inskip Point, stripping chunks of sand away from the beach. It appeared after the recent deluge near where vehicles are loaded onto the barges to go to Fraser Island. Vid: Wayne Kerr. https://t.co/dSgFbiE9NM #7NEWS pic.twitter.com/7zmXEc5dhk
— 7NEWS Sunshine Coast (@7NewsSC) April 8, 2021
I have posted about these retrogressive landslides at Inskip Point previously. This is another example of a Retrogressive Breach Failure, not a sinkhole.