9 July 2020
Shimen County, Hunan Province: a 3 million cubic metre rainfall triggered landslide
Heavy rainfall continues to fall across a swathe of Southern China, causing landslides and floods. This morning the national observatory has issued orange rainfall warnings for Jiangxi, Fujian, Zhejiang, Hunan and Guizhou, forecasting up to 280 mm of rainfall, with peak intensities of over 700 mm per hour. This is landslide-inducing levels of precipitation.
In Shimen County in Hunan Province the rainfall has triggered a very large landslide that has destroyed five houses. The landslide was caught on video, uploaded to Youtube. It is something of a medley of segments, but nonetheless captures failures from the rear scarp and the flow behaviour of the main mass.
There is a longer and more detailed version of this video on Youtube too. You will need to forgive the loud and unnecessary music, but it captures the movement of the main body of the slide well:
I have struggled to find a decent image of the landslide – this is the best that I have managed so far, from the start of the video (and hence the play arrow):-
Quickslide 1: A fatal landslide in Hubei province
Meanwhile, a landslide buried nine people yesterday in Yuanshan Village of Dahe Township, Huangmei County in Hubei province, again triggered by heavy rainfall. Xinhua reports that one of the victims has been recovered alive, whilst four remain buried.
Quickslide 2: The aftermath of the Myanmar jade mine landslide
Interestingly, there are news reports that the Myanmar Government is taking action to identify those responsible for the jade mine landslide in Myanmar, which killed over 160 people. The Khmer Times reports that two high ranking military officers, the Kachin Security and Border Affairs Minister Colonel Nay Lin Tun and an unnamed officer, have been dismissed. ECNS reports that a formal investigation of the landslide is under way.
7 July 2020
Erzincan: a very interesting mudflow in Üzümlü, eastern Turkey
On 2 July 2020 a large and interesting mudflow occurred at Günebakan in the Erzincan area of eastern Turkey. The Turkish news site AA has an image of the aftermath of the landslide:-
The landslide reportedly destroyed two houses and a number of stables, as well as killing some livestock. Fortunately no-one was killed.
The most interesting aspect of this landslide is that the latter phases of it were captures on a video that has been uploaded to Youtube by the Turkish news site Erzincan Haber :-
This video gets really interesting at about 26 seconds, when a small flow is captured travelling down the channel. At about 40 seconds it becomes fascinating as a much larger flow enters the system and propagates through the mud. The video captures really well the complex flow properties of these materials – initially the wave travels over the top of the existing deposit, but later on it becomes a waves that travels through the deposit. It’s very interesting behaviour that will provide insight for the landslide modelling community.
Thanks to Tolga Görüm for highlighting this one to me.
Quickslide 1: Lidar data of the Old Fort landslide
An excellent presentation of the new Lidar data from the Old Fort landslide has been posted online by the British Columbia Ministry of Transportation and Infrastructure. Thanks to Susan DeSandoli, who is kindly keeping me updated about this interesting landslide.
Quickslide 2: The rising toll from the heavy rains in Japan
The ongoing spell of the exceptional rainfall in Japan continues to generate extensive landslides and widespread flooding. Reuters reports that 44 people have now been killed and a further ten people are missing. The rainfall is steadily moving eastwards and is likely to last until at least Wednesday.
6 July 2020
Ashikita: a large landslide in the Kumamoto region of Japan
Japan has once again suffered from exceptional rainfall in recent days, with the Kumamoto region of the island of Kyushu bearing the brunt. Landslides and flooding have occurred across a wide area. Further rainfall was forecast for Sunday evening. There is a good Wikipedia providing some details about this rainfall event. It reports peak rainfall intensities of about 100 mm per hour.
At Ashikita in Kumamoto Prefecture a large landslide occurred on a steep, forested mountain slope. Teller report has a good overview image of the landslide:-
Whilst there is a good drone video of the landslide on Youtube, posted by Ruptly:
This landslide reportedly occurred at 11:40 on 4 July 2020. When large landslides occur there is often a default view that human modification of the landscape, especially the removal of trees, is the cause (and often this is the case). This landslide appears to demonstrate that, as all landslide researchers know, failures are a natural process that can occur on undisturbed forested slopes.
Quickslide 1: An update on the Myanmar jade mine landslide
Loss of life from the landslide at a jade mine in Kachin State has reached 174 people, with a further 54 people reported to have been injured. An investigation of the landslide is apparently underway. Interestingly, the State Counsellor (equivalent to Prime Minister) Aung San Suu Kyi has blamed the disaster on joblessness, which forces people to scavenge for jade on the soil tips.
Quickslide 2: a dramatic rockslide in Idaho
A large and dramatic rockslide occurred on 3 July on US route 95 at Sheep Creek near to Riggins in Idaho. Yahoo News has a video of the incident. The road remains closed, and there is concern about further potential instability on the rockslope as a large crack has developed.
3 July 2020
The Dawn of Hope peat slide: understanding the source area
My tweet yesterday linking to the remarkable video on Youtube by John Flynn that shows the full extent of the Dawn of Hope peat slide attracted a great deal of attention. One of the aspects of landslides that I enjoy the most is that, 30 years into my professional career, I still find slides that cause surprise. This is one, without doubt.
The video provides a source to toe record of the landslide, but of course it is the source area that has generated the most interest. I can only speculate on what is going on here – others will investigate it properly, and I will post their findings when published if possible. On Twitter some suggested that this might be a lateral spread that transitioned into a flow slide. I would speculate that this is unlikely. This image shows the lower part of the source area, and the transition zone into the channelised flow:-
I would hypothesise that the slide initiated here as a bog burst and then retrogressed to create the extraordinary landform seen in the upper reaches of the source area:-
These are extensional landforms, which have generated because there was space vacated by the initial bog burst. The line of trees, mostly intact and upright, following the drainage line, is remarkable. It shows that the failure has propagated up the channel, and that in the channel itself mobility is quite high. The peat adjacent to the channel has failed, but with much lower mobility.
To understand landslides in peat there are a few important aspects to consider:-
- Peat is a predominantly organic material, with some clay and silt and a very large amount of pore space. This means that it has an unusually low density compared with other geomaterials. A typical density for peat is about 400 kg per cubic metre – less than half of that of water – so rafts of peat can literally float.
- The peat itself has low compressive strength, but is quite strong in tension. This is because the body of the peat consists of organic fibres. This may be the reason that the blocks have remained intact.
- Failure in peat slides very often occurs at the boundary between the peat and the underlying substrate. I think there is some evidence that this is the case here.
So, my hypothesis would be that the extreme rainfall, perhaps aided by piping in the peat, led to very high pore water levels in lower part of the topographic depression shown in the first image. This failed to generate a bog burst, and a large amount of degraded organic material vacated the depression and entered the channel. It clearly entrained considerable amount of material from within the channel, and of course the structure of the peat was rapidly lost in the turbulent flow, creating a slurry with high mobility.
Back in the source area, the now vacated depression allowed failure of the adjacent blocks. Failure propagated upwards through the depression, aided by the high pore water pressures. But of course these materials are highly permeable, so failure also induced rapid drainage, especially away from the channels. Thus, the pore water pressures at the base of the blocks quite rapidly declined, leaving the peat rafts stranded.
The video also shows the areas of inundation (there is more than one) downstream:-
The level of damage here is undoubtedly high.
I welcome comments about this landslide, and my interpretation of it. I’m aware that the comment function is not working correctly at the moment, so I will try to add the key comments to the main text below when I get a chance.
Quickslide 1: The Sate Mu jade mine landslide
Loss of life from the Sate Mu Jade Mine landslide is now at least 166 people, making it the worst landslide of 2020 to date. Heavy rainfall is hampering the rescue, so the number remaining missing is unclear. A much better version of the video of the failure has now been tweeted. Tragically, the video appears to show a very large number of people on the slope at the time of failure:
— ABC News (@ABC) July 2, 2020
Quickslide 2: NASA imagery of the Achoma landslide
NASA has now posted before and after satellite imagery of the Achoma landslide in Peru. It is useful, but is less impressive than the Planet Labs image that I posted a few days ago.
2 July 2020
Sate Mu village: another dreadful jade mining landslide in Myanmar
Today (2 July 2020) another dreadful landslide has occurred in the Hpakant jade mining area of Kachin state in Myanmar. Loyal readers will know that this is the most frequent location for major landslide tragedies anywhere in the world.
The landslide this morning occurred close to Sate Mu village in Hpakant. The latest figures in terms of lives lost are given on the Facebook Page of the Myanmar Fire Service, who report 113 victims recovered so far, with search and rescue operations continuing. There appear to be fears that there may be many more people buried.
Earlier reports suggest that this was a failure of a tall slope (the report suggests 304 metres, but this seems surprising) on to people scavenging for jade. In general people who undertake this type of scavenging work on the spoil piles from the mining operations, so this may well be a mine waste failure once again. The landslide appears to be associated with heavy monsoon rainfall.
Huge care is needed in the interpretation of images in newspapers from these types of events as they frequently recycle pictures from earlier events. However, the this image of the Sate Mu landslide from the Myanmar Fire Service is probably genuine:-
This would seem to indicate that this video, which was posted to Twitter, might also be genuine. I don’t think I have seen this video before, and in basic configuration it appears to fit the situation. The jury is still out though:-
Hopefully more will emerge in the next day or so, but the Sate Mu landslide might well be the most deadly landslide in the jade mining areas of Myanmar to date. In September 2018 I summarised the known landslide fatalities in Hpakant to that point.
Quickslide 1: At least six people killed in landslides in Brazil
A rapidly intensifying cyclone caused heavy rainfall in Santa Catarina in southern Brazil. Some news reports indicate that six of the fatalities were caused by landslides.
Quickslide 2: Further landslide losses in Assam
Heavy rainfall in Assam has caused a further round of landslides and flooding in northern India.
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.