1 July 2020
Dawn of Hope: a major peat landslide in County Leitrim, Republic of Ireland
Exceptional rainfall on Sunday 28 June 2020 triggered a major landslide at Dawn of Hope in Count Leitrim in the Republic of Ireland. This is an unusual landslide – the failure of a peat bog. Peat bog landslides are remarkable for their mobility and for the damage that they can cause.
The Irish Farmers Journal has a report about this event, which has seen the failure of a large area of peat bog and deposition on a large area too. The location is 54.201, -8.086 if you wish to take a look.
The best understanding of this remarkable failure can be gained from a series of three drone videos posted to Youtube by Garadice 2000. The best overview can be gained from the second in the series, which at the end appears to provide a view of the source area of the landslide:-
Meanwhile the video in the following tweet provides a really good impression of the long track of the landslide:-
Drone footage shows the cumulative effects of wide scale plantation @coilltenews forestry at the Dawn of Hope Bridge bog slide in Drumkeeran No EIA on any plantation in #Leitrim to date & almost 20% of the total county planted. It is having a MASSIVE environmental impact pic.twitter.com/9aC0yIsILJ
— Edwina Guckian (@EdwinaGuckian) June 30, 2020
The landslide has caused extensive damage downstream. This image, from the Irish Farmers Journal, shows the inundated area:-
Quickslide 1: The Old Fort landslide has slowed
The Old Fort landslide in Canada has slowed considerably, with a reported movement rate of about 10 cm per hour. Unfortunately, heavy rainfall is forecast for the next few days.
Quickslide 2: More heavy rainfall in China
30 June 2020
The 18 June 2020 Achoma Landslide in Peru
On 18 June 2020 the very large Achoma Landslide occurred in valley of the Rio Colca in Peru. Many thanks to Gael Araujo of the Geological Service of Peru for highlighting this one to me, and to Robert Simmon of Planet Labs who independently identified it from satellite imagery. As far as I am aware, this landslide has not been reported in the English language media, but it is a very large, valley-blocking failure. La Republica has some drone imagery that gives a good impression of the scale of the landslide:-
As the image shows, the landslide has blocked the Rio Colca, allowing a lake to form. As of yesterday, the volume of the lake was about 2 million cubic metres. A state of emergency has been declared for the area, lasting 60 days, whilst efforts are being undertaken to drain the lake. The video below, collected by Ingemmet, should provide a good impression of the scale of this landslide:-
As noted above, Planet Labs has collected an excellent satellite image of this landslide:-
This image clearly captures the scale of both the landslide (which covers an area of about 40 hectares) and the developing barrier lake.
On reflection 1: A rare peat bog landslide in Eire
It appears that a large peat bog landslide occurred in North Leitrim in Eire over the weekend, triggered by heavy rainfall. Does anyone have any more information?
On reflection 2: The Tylerstown landslide – an update
29 June 2020
Vitalj, Bosnia and Herzegovina: a damaging landslide on 23 June 2020
Guest post by Damir Hatunić
In the early hours of 23 June 2020 a landslide occurred at Vitalj in Kladanj, northeastern Bosnia and Herzegovina. This landslide interrupted traffic on the main road, the M-18, between Sarajevo and Tuzla. The location of the landslide is 44.242, 18.706.
This was one of a dozen landslides triggered in the area after three days of rainfall combined with favourable antecedent soil moisture conditions developed since the last week of May according to The Federal Institute for Hydrometeorology in Bosnia and Herzegovina.
The dimensions of the landslide are 70 metres in length and 20 to 30 metres in width, with the thickness of the initiating material estimated at between 1 and 2 metres.
The landslide took a place on a eastward slope, which has 16° of average inclination and is artificially modified with cut and fill, where the regolith layer has formed on Jurassic claystones. It is notable that the slope was completely deforested 20 years ago, but the forest has subsequently undergone regrowth. Such conditions are very common in the area of northeastern Bosnia, which is a largely landslide-susceptible region.
The mechanism of movement here is predominantly translational and this slide can be classified as an earth-slide with transformation into a mudslide at the toe zone. The movement velocity during main phase, according to eyewitnesses, was in decimeters per second. Shortly after the landslide initiated, the responsible authorities responded with heavy equipment, so that part of the landslide was cleared from the road by the end of the day (according to Klix.ba).
This video provides more detail about the landslide:
On reflection 1: Another near miss on the UK coast
The Metro has reports and images of another near-miss when a landslide from a coastal cliff came close to burying people on the beach. Whilst the reporting of these events can be a bit dramatic, it is only a matter of time before there is another tragedy.
On reflection 2: continuing heavy rainfall in China
Heavy rainfall continues to cause significant landsliding in China. Xinhua reports a further 12 fatalities in Mianning County in Sichuan Province, with 10 people killed and seven reported to be missing. Meanwhile, a rainfall alert has been issued for today for a swathe of China, including the provinces of Zhejiang, Anhui, Hubei, Jiangxi, Hunan, Guizhou, Yunnan, Sichuan, Hebei and Shandong.
25 June 2020
The Old Fort Landslide: 160 m of movement so far
The reactivation of the Old Fort landslide in Canada continues to cause substantial disruption to the population of the Old Fort subdivision. Reports yesterday indicate that the landslide had moved about 160 metres in the most recent movement event, at rates of about 2 metres per hour. There is an excellent archive of images in a post on the Alaska Highway News website.
The scale of the movement can be seen in these two Planet Labs images of the site, taken five days apart:-
Note in particular the displacement of the road, which can just be made out in the second image. The toe of the landslide has also displaced, and there are signs of significant amounts of deformation towards the crown of the landslide.
In the gallery of images the most interesting one may be this image of the crown area of the landslide:-
There is much to note in this fascinating image. The main slide extends into the distance – the now destroyed road can just be seen. In the foreground the rotational component of the system is clear. On the lower left of the image there is a rear scarp, several metres high. Below this (in the centre right of the image) there is a large block that has displaced and rotated. This block is starting to break up – note the large tension crack running across it, and the rent on the right hand side of the block. Finally, note the very clear lateral shear just to the left of centre of the image, beside the hillock.
Given the weather, I would expect movement of this slide to reduce in the coming days. However, the system is primed to reactivate in future heavy rainfall events, with similar impacts. Stabilisation of such a large, complex landslide is unlikely to be economic.
This landslide reminds me of the Tessina landslide in northern Italy. Back in the mists of time I wrote a paper (Petley et al. 2005) that examined the ways in which the style of movement of these landslides change as the blocks that feed the system transition from rotational movement to flow.
On reflection 1: The building Asian monsoon
The summer monsoon is rapidly developing across Asia. In Nepal, warnings have been issued for heavy rainfall today amid reports of ongoing landslide induced disruption. In China, heavy rainfall warnings have been issued across a wide area.
On reflection 2: Heavy rainfall causes debris flows in Ukraine
Meanwhile, very heavy rainfall in Ukraine has induced debris flows and flooding, impacting in particular on the ski resort at Bukovel.
Reference and acknowledgement
Petley, D.N., Mantovani, F., Bulmer, M.H.K.., and Zannoni, F. 2005. The interpretation of landslide monitoring data for movement forecasting. Geomorphology, 66 (1-4), 133-147.
Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
Thanks to Susan DeSandoli for highlighting fascinating reports on the Old Fort landslide.
23 June 2020
The Gjerrild Klint landslide on the east coast of Jutland, Denmark
Guest post by Gregor Luetzenburg, Kristian Svennevig & Marie Keiding
Researchers from the University of Copenhagen and the Geological Survey of Denmark and Greenland were recently informed about a landslide at Gjerrild Klint at the Danish Kattegat coast north of the City of Aarhus (56.513 N, 10.865 E). Based on observations made in PlanetScope and Sentinel 2 scenes, the landslide most probably occurred at the beginning of March 2020, but was first discovered and reported by locals about three months later. A period of unusually low precipitation from March to June 2020 preserved most of the distinct young morphological features in the soft glacial till, such as pinnacles on the main body of the slide.
Landslides occur regularly in Denmark, but fortunately most occur as earth slides and flows along the sparsely populated coastline, and thus do not lead to fatalities. Most damage reported is to holiday homes, which are common along the coast. This specific landslide is a good opportunity for us to investigate the complex interplay of geology, hydrology, climate, wave erosion and land use leading to slope failure.
The area covered by the landslide is around 2,500 m² (70 x 35 m). The height of the cliffs on the coast is around 25 m. Having the shape of a textbook landslide, the Gjerrild Klint landslide features the main characteristics of a rotational landslide. A clearly definable crown at the top of the cliff with smaller crown cracks covered by the surrounding crops can be observed. The head of the slide, beneath the main scarp, is characterized by parallel displaced and rotated blocks with minor scarps in between. At these blocks the topsoil is still intact allowing the remaining crops to continue to grow.
Water supply to the slide is increased by the broken artificial drainage system of the overlying cultivated field. However, drainage of the slide’s surface is poor leading to ponding in the back-tilted areas. Further down, the slide shows minor scarps and transverse cracks. At the foot of the slide, waves have already started to erode the toe. Uplifted beach deposits can be seen demonstrating the rotational process of movement of the slide. Several minor toe collapse slides can be observed as well.
The cliff at Gjerrild Klint consists of alternating layers of glacial till and clay and several older vegetated slides can be seen next to the new one. This indicates that the Gjerrild Klint slide is one of many in a long sequence of rotational slides, forming the local coastline by occasional but consecutive mass movements. The main conditioning factor here is probably a local glaciolacustrine clay unit located just at sea level and observed in the slide toe on several places, probably acting as the sliding plane. Intense agricultural land use and manmade drainage systems may further precondition landslide processes, by redirecting the naturally vertical flow of water laterally towards the cliff. Moreover, wave erosion at the toe of the cliff is constantly removing material, destabilising the prevailing equilibrium. February 2020 provided optimal conditions for triggering the landslide with 103 mm of precipitation during the month in the area of the Gjerrild Klint landslide – a record for the highest amount of rainfall since the beginning of the measurements in 1874. The slide was thus most probably activated by water infiltration into the glaciolacustrine clay reducing the friction. Shifting towards a surge in weather extremes and rising sea levels under a warming climate, Denmark is likely to experience an increase in this type of landslide activity in the next years and decades.
On reflection 1: Recent landslides in Darjeeling
The wonderful Save the Hills blog has a good post about landslides triggered by heavy rainfall on 11 – 13 June 2020 in Darjeeling, highlighting the role of humans in increasing landslide susceptibility in this area.
On reflection 2: The summer monsoon is rapidly developing across South Asia
As the rainy season gets under way across South Asia, landslides are starting to inflict losses. In the last day or so three people (including two children) were killed in a landslide in Sikkim in India, three people were killed in a landslide in Palpa in Nepal and cross-border trade between Tibet and Nepal has been halted by landslides near to Tatopani.
22 June 2020
The Old Fort landslide has reactivated – about 100 m of new movement
Back in October 2018 I wrote about the Old Fort landslide, a large earthflow that has affected access to a subdivision close to the town of Fort St John in British Columbia, western Canada. In recent days a period of heavy rainfall has reactivated the landslide, which has shown an impressive amount of movement. Energetic City, a local news outlet, reports that the landslide has moved about 100 metres. Their report includes this impressive image of the disruption to the access road to the Old Fort subdivision:-
Note the very impressive displacement of the road shown in the image, which also captures the extensive landslide activity on the margins of the main slide.
The Peace River Regional District (PRRD) has an emergency response website, providing updates to the community affected by the landslide. About 150 people live in the Old Fort Subdivision. The PRRD has provided the following map that shows the main features of the landslide:-
Many thanks to Susan DeSandoli, who highlighted that this really interesting landslide has reactivated.
On reflection 1: a valley-blocking landslide in Nepal
The Kathmandu Post reports that a large landslide on Sunday 21 June 2020 partially blocked the Arun River in Makalu Rural Municipality, Sankhuwasabha District. A lake has formed, although this does not appear to be particularly large. Communities downstream have been put on alert.
On reflection 2: A fatal landslide in Côte d’Ivoire
On 18 June 2020 a large landslide at Anyama, a community located north of Abidjan in Côte d’Ivoire, killed 13 people. A news report on the Medafrica website suggests that this was the failure of a railway embankment, possibly caused by blocked drainage.
18 June 2020
Quick clay landslides: an online documentary about Rissa
The recent interest in quick clay landslides, triggered by the remarkable video from Alta in Norway, has led to a number of questions as to the mechanisms of these strange failures. Loyal reader George Haeh kindly pointed out that there is a wonderful video, produced by NGI, that seeks to explain the famous 1978 Rissa landslide in Norway. This was the first quick clay landslide to be caught on video; the recording remains a classic. The NGI documentary has been posted to Youtube. It includes the famous footage of the landslide in action.
The video is most definitely of its time, complete with haunting music, and it’s highly instructive in terms of explaining the sequence of events at Rissa, and the underlying processes. I especially recommend the sequence from about 2 minutes 34 seconds into the recording, which seeks to explain the mechanics of quick clays. The sequence includes an initially intact block of quick clay being subjected to a load that exceeds its strength:-
During failure the video shows the rapid change in the properties of the clay:-
The video then goes on to show that remoulding the clay, without adding any fluid, leads to a complete change in the material properties, that now behave as a liquid:-
Perhaps the most interesting part of the video is the response to the addition of a small amount of table salt. The quick clay quickly regains much of its strength, to the extent that the technician can stand a knife up in the material:-
I have not seen such a clear explanation of the mechanics of quick clays.
On reflection 1: A valley blocking landslide in Sichuan
A large valley blocking landslide in Danba County in Sichuan, China has caused extensive flooding. 20,000 people have been evacuated.
On reflection 2: A mudslide-induced house collapse in Nigeria
16 June 2020
New landslide videos: Russia and California
A couple of new landslide videos have emerged that are worth a look. Whilst they are not as dramatic as the quick clay landslide video from Norway, they are nonetheless interesting. The first was highlighted to me by the famous Russian landslide scientist, Alexander Strom. The location is uncertain – it is probably somewhere in Russia. Unfortunately I cannot embed this one, so you’ll need to follow this link.
This is clearly a failure in a large mine. The magnitude is large, although it is hard to get a sense of the depth of the view. Interestingly, early in the video a large quarry truck lumbers up the haul road on the right even though the foot of the slope was actively failing:-
To me this suggests that the landslide had not been anticipated, or that it is larger than expected.
It would be good to get more information about this failure, and about the outcome of the collapse (which appears to still be in progress at the time of the video).
Meanwhile, on Youtube there is an interesting video taken on Highway 101 in Sausalito, California. The video is from a dashcam, and captures the moment when a small rockfall impacts on the road directly in front of the car. Be careful as the video captures an understandable profanity from the driver, who was definitely in the wrong place at the wrong time:-
The video captures the fragmentation of the rock blocks rather beautifully:-
According to the text accompanying the video, the damage to the car cost $21,000 to repair. It is interesting that this failure occurred on a sunny day. This one was highlighted to me by loyal reader Fabien, many thanks.
On reflection 1: Another railway landslide in the UK
A landslide has blocked the line between my home town Sheffield and Scunthorpe. The disruption is expected to last 10 days.
On reflection 2: Images of the Norway quick clay landslide
Louise Vick of UiT The Arctic University of Norway has tweeted some images of the aftermath of the Norway quick clay landslide, collected during a field visit:
Nipped up to Alta today to collect some data at the Kråknes #landslide. I learned some surprising facts about the sequence of events (eg the slide comprised many(!) smaller failures) and saw some crazy features (eg natural pipes in the soil profile and exposed sliding surfaces). pic.twitter.com/g6ZfcMQTQT
— Louise Vick (@LandslideLouise) June 15, 2020
Her observations about the site are interesting. A follow up tweet included a further set:-
Hope these are of interest pic.twitter.com/OCwBGNyPOk
— Louise Vick (@LandslideLouise) June 15, 2020
15 June 2020
The 15 March 2019 Xiangning landslide in Shanxi Province, China
On 15 March 2019 a large landslide occurred in Xiangning County in Shanxi Province in northern China. The landslide, which occurred in loess, destroyed a number of residential buildings and the local health centre. In total 20 people were killed and a further 13 were injured. A paper has recently been published in Natural Hazards (Zhao and Zhao 2020) that provides some more detail of this disaster.
The authors provide this highly informative montage of photographs and drawing to illustrate the event:-
This is quite an unusual loess landslide as it had the form of a slump with limited runout. As the image above shows, the main slump block did not fragment, and one of the larger buildings remained remarkably intact. The landslide had a volume of 73,000 cubic metres and the displaced block was 125 x 80 metres.
Interestingly, Zhao and Zhao (2020) could find no external triggering event, such as an earthquake or intense rainfall. They concluded that the landslide was the result of natural degradation of the loess, perhaps accelerated by human activity such as deforestation.
An unusual aspect of this paper is that it provides some detail about the rescue efforts for the Xiangning landslide:-
Judging from the rescue situation, the on-site rescue environment was highly complicated, challenging, and high risk. First, the landslide had a large volume and deeply buried pressure; those factors considerably influenced the location of rescue site searches. Second, the location of the landslide was on the hillside and caused a complicated situation, while the mountain road was meandering and narrow. Thus, the work surfaces of the rescue operation were small, large machinery could not be used or even come close to the scene, and the efforts of small rescue equipment were limited. Third, the soil of the landslide body was flaccid and the structure was unstable. During the rescue, landslides occurred several times, cracks became larger, and rockfall transpired. Many large building wreckages were scattered on the collapsed mountain; the height from the top to the bottom of the mountain measured dozens of meters, and the slope was almost vertical. The wreckages of the buildings fell off, likely causing harm to the rescuers below who were not evacuated in time.
This is a good illustration of the multiple challenges faced in the aftermath of such disasters.
On reflection: The first large landslide disaster of 2020 in Nepal
A large rainfall-induced landslide at Kushma in Durlung, Parbatin Nepal on Saturday night killed nine people. The summer monsoon is becoming active in South Asia.
Zhao, B. and Zhao, Y.Q. 2020. Investigation and analysis of the Xiangning landslide in Shanxi Province, China. Natural Hazards https://doi.org/10.1007/s11069-020-04109-2
11 June 2020
Landslides in Art Part 33: Vue du vallon entre le Rossberg e le Rigi apres la terrible catastrophe du 2e Septembre 1806
Landslides in Art Part 33: Vue du vallon entre le Rossberg e le Rigi apres la terrible catastrophe du 2e Septembre 1806
The British Museum collection includes a print of a painting by Gaspar Rahn entitled Vue du vallon entre le Rossberg e le Rigi apres la terrible catastrophe du 2e Septembre 1806. This translates as View of the valley between Rossberg and Rigi after the terrible disaster of 2nd September 1806.
This is the print:-
This painting clearly shows a very large landslide with a long runout. The material involved in the failure is clearly mostly large rock blocks. Note in the foreground clear damage to buildings, and considerable strewn debris, suggesting that the landslide generated a displacement wave in Lake Lauerz.
This painting depicts of the aftermath of the so-called Goldau Landslide in Switzerland, which has featured in this series previously thanks to a painting by Joseph Mallord William (JMW) Turner. As I noted then, the Goldau landslide was triggered by heavy rain, with an estimated volume of 120 million cubic metres, covering an area of about 20 square kilometres. The landslide, and the tsunami it created on Lake Lauerz, destroyed 111 houses, 220 farm buildings and two churches, resulting in the deaths of 457 people. There is a brief write up of the Goldau landslide on the Scientific American blog, whilst another article on the same site notes that this was the first landslide to be investigated in depth by geologists.
On reflection 1: Landslides at the start of the rainy season in China
Xinhua is reporting multiple landslide fatalities triggered by heavy rainfall in China. For example, in Baojing County in Hunan Province, heavy rainfall has triggered landslides and floods that have destroyed several village houses, killing six people, with a further person missing and three others injured.
On reflection 2: How medieval Europe recovered from earthquakes
The Conversaton has a very nice article on the ways in which societies in medieval Europe recovered from destruction earthquakes. The impact of coseismic landslides and rockfalls features heavily.