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5 June 2020

The Alta Quick Clay Landslide: further footage

The Alta Quick Clay Landslide:- further footage

Further footage has been posted to Youtube showing the Alta Quick Clay landslide on 3 June 2020, which I featured yesterday:-

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This new film provides some additional footage of the site prior to the main slide and some drone footage of the aftermath.  In both cases the imagery is very revealing.

The early footage was also filmed by Jan Egil Bakkerby, who shot the main video that went viral yesterday. It shows the site shortly before the main failure.  Interestingly, it clearly captures the aftermath of the earlier failures to which I alluded:-

The Alta Quick Clay landslide

A still from new footage capturing the Alta Quick Clay landslide. This image shows the aftermath of an earlier failure. Footage by Jan Egil Bakkeby, posted to Youtube.

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The footage confirms that a substantial failure occurred prior to the main Alta quick clay landslide. There is a large vacated scar in the background, whilst in the foreground slumping has developed.

The video then includes the original footage of the landslide before switching to drone footage of the aftermath.  There are a couple of things to note here.  First, further failures have developed even after the viral video was captured.  In particular, the landslide has developed laterally, so that a larger portion of the coast has now been affected:-

Alta Quick Clay landslide

A still from new footage capturing the Alta Quick Clay landslide. This drone image shows the extensive area affected by the multiple failure events. Footage by posted to Youtube.

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Second, at about 7 minutes 30 the footage captures a small retrogressive landslide in the rear scarp of the landslide:-

Alta Quick Clay landslide

A still from new footage capturing the Alta Quick Clay landslide. This drone image shows a small secondary failure in the headscarp. Footage posted to Youtube.

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Notable here is the highly mobile nature of the failed material.  This material was sufficiently strong to stand in a near-vertical scarp but, once failed, flows like a fluid.  This is a good illustration of the very challenging geotechnical properties of quick clay.

Finally, for today, the text accompanying the video suggests that the first failure was observed at this site on 29 May 2020 by the Norwegian Water Resources and Energy Directorate (NVE).

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On reflection 1: warnings of further landslides in Norway

NVE has warned that there is the possibility of further landslides in Norway. “It’s important to stress that there’s still a lot of snow in the mountains,” Bjørn Sønju-Moltzau, a hydrologist at state waterways agency NVE, told state broadcaster NRK on Thursday. “We’ve only gotten rid of around half of it. That means we still have the rest of it in the central and northern parts of the country.”

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On reflection 2: Looking for southern Appalachian rockfall scars using a high-resolution LiDAR dataset

The Field blog, also hosted by AGU, has a nice article about the use of LIDAR for mapping the scars and tracks of rockfall boulders.

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4 June 2020

Alta: a truly remarkable video of a quick clay landslide in Norway

Alta: a truly remarkable video of a quick clay landslide in Norway

One of the top ten landslide videos of all time was captured yesterday at Kråknes in Alta, in the north of Norway. This video shows what is almost certain to be a quick clay landslide.  It occurred in the morning of Wednesday 3 June 2020; the video has been posted to Youtube. If this video ceases working then it can also be viewed here.

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VG.no has an article (in Norwegian) that explains the context of the video. It was collected by the owner of one of the houses, Jan Egil Bakkeby. He notes that they saw a tension crack downslope from their cabin on Tuesday evening, but chose to stay overnight.  It rained on Wednesday morning, after which the landslide occurred. He fled from the house and climbed the hill, and then shot the video.

The landslide appears to have occurred as a coherent raft in the first instance:-

Alta quick clay landslide

The initial phases of the Alta quick clay landslide. Still from a Youtube video collected by Jan Egil Bakkeby.

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There is a change in gradient of the underlying bedrock towards the sea, which caused the raft to start to fragment in the latter stages:-

Alta quick clay landslide

The latter phases of the Alta quick clay landslide. Still from a Youtube video collected by Jan Egil Bakkeby.

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There is a great deal of valuable information in the video about the behaviour of the landslide itself, and the way that it generated a displacement wave.

I suspect that this was the second phase of the landslide. The very early shots seem to show considerable existing damage at the front of the slide, on the right side of this screenshot:-

Alta quick clay landslide

The very early phases of the Alta quick clay landslide. Still from a Youtube video collected by Jan Egil Bakkeby.

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Quick clays are glaciomarine materials that have strange properties.  When disturbed they are very weak – indeed their behaviour is similar to that of a fluid.  But undisturbed they are much stronger, primarily because of the role of salt, which glues the particle structure together.  When this structure is disturbed, the quick clay rapidly weakens, allowing these spectacular landslides to form.

I have featured a number of other quick clay landslides over the years, including examples from Sweden, Norway and Canada, and a similar type of landslide from Brazil.  The most famous example is the Rissa landslide, also in Norway, for which another excellent video is available.

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On reflection 1: Further landslides at Eastchurch in Kent

Yesterday further failures occurred at Eastchurch in Kent, the site of the coastal landslide that destroyed a house over the weekend.  Further properties are now at risk.

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On reflection 2: saving lives at Brumadinho

An interesting paper is available for online review in the journal NHESS looking at ways in which lives could have been saved during the Brumadinho tailings dam failure last year.

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Acknowledgement

Many thanks to the various people who highlighted this to me via this site, by email and on Twitter. Your help is much appreciated.

 

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2 June 2020

The evolution of co-seismic landslides: the 2005 Kashmir earthquake

The evolution of co-seismic landslides: the 2005 Kashmir earthquake

As I have documented on this site on many occasions, large earthquakes are a highly efficient way to generate landslides in mountainous areas. Landslides kill people directly, but also act to increase the losses from building collapses by preventing access to rescue personnel and impeding the provision of medical assistance.  Landslides also prolong the impacts of the earthquake, often for years. Typically landslides occur extensively in heavy rainfall events in the years after the earthquake, causing high levels of damage and loss of life.

The latter point means that understanding the evolution of slopes after large earthquakes is important.  There are many unanswered questions – for how long would we expect to see an elevated level of landsliding? What controls this length of time? And how (and indeed why) does the decline in landslide activity actually occur?

A new paper in the journal Geomorphology (Shafique 2020) explores this issue for the 2005 Mw=7.6 Kashmir earthquake in Pakistan and India. This is one of the worst landslide disasters of the last two decades, with thousands of landslide related fatalities. The author has used archive SPOT satellite imagery to map the landslides in the earthquake affected area of Pakistan, in the vicinity of the towns of Balakot and Muzaffarabad, before and after the earthquake.

The results of the study are summarised in this graph:-

Kashmir landslides

The evolution of the surface area of landslides associated with the 2005 Kashmir earthauke. Image by Shafique (2020).

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Prior to the earthquake Shafique (2020) mapped 37 landslides in the study area. The first mapping exercise after the earthquake used images dated 20 October 2005, 12 days after the main shock.  The number of landslides had increased to 219, an increase of about six times.  This image, which I took in early 2006, shows some of the landslides triggered by the earthquake:-

Kashmir landslides

Landslides triggered by the 2005 Kashmir earthquake.

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The satellite mapping is only able to identify the larger landslides, so the inventory should not be used to determine the total number of landslides triggered.  As the graph shows, by the time of the next mapping exercise, in 2010, the number of landslides had started to decline.  This reduction accelerated, such that by 2014 the number had reduced markedly. By 2018, the number of landslides was close to the number prior to the earthquake.

Thus, in the Kashmir earthquake case it appears that it has taken in the order of 13 years or so for the level of landslide activity to decline back to pre-earthquake levels.  Shafique (2020) rightly highlights that there is an extra factor in play.   Other studies have indicated that the number of landslides increased by about 250% in the first summer monsoon (in 2006) after the earthquake. This would certainly accord with my own observations – I was there in May 2006, shortly before the monsoon began, and was deeply concerned by the number of partially failed slopes:

Kashmir landslide

A partially failed slope in Kashmir, taken before the 2006 monsoon season

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Thus, the peak landslide area was probably higher than the graph from Shafique (2020) might indicate.

The decline in landslide activity from this study has taken longer than has been the case for some other large earthquakes.  Shafique (2020) suggests that a major factor in the reduction might be the regrowth of vegetation.  Perhaps the climate of Kashmir, which is arid outside of the short monsoon season, means that this process takes longer than in many other mountain chains.

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On reflection 1: A lucky escape!

Climbers and hikers in Vermont had a lucky escape when boulders  tumbled down the mountainside at Smugglers Notch.

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On reflection 2:

The fall-out from the cliff collapse at Eastchurch in Kent continues. Ironically, the Daily Mirror reports that the house damaged by the landslide was called Cliffhanger.

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Reference

Shafique, M. 2020. Spatial and temporal evolution of co-seismic landslides after the 2005 Kashmir earthquake. Geomorphology, 362, 107228. https://doi.org/10.1016/j.geomorph.2020.107228

 

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1 June 2020

Eastchurch – a coastal landslide in Kent, SE England

Eastchurch – a coastal landslide in Kent, SE England

Over the weekend the newspapers in the UK have been reporting two coastal landslides that occurred at Eastchurch on the Isle of Sheppey in Kent.  These two landslides, which occurred at the same site, have damaged a house.  The first failure occurred at 10 pm on Friday 29 May 2020:-

Eastchurch landslide

The first landslide at Eastchurch on the Isle of Sheppey in Kent. Image via the Independent.

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This is quite an interesting landslide, with an unusual linear geometry in the rear scarp, similar to a wedge.  The Isle of Sheppey consists mainly of London Clay, which is well known for the presence of fissures and joints.

Over the weekend the situation deteriorated substantially, and on Sunday 1 June 2020 a further substantial landslide occurred, causing damage to the house closest to the cliff:-

Eastchurch landslide

The second landslide at Eastchurch on the Isle of Sheppey in Kent. Image via the Independent.

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The site of the landslide is 51.418, 0.873, as shown below.  I have marked the rear scarp of the second landslide at Eastchurch:-

Eastchurch landslide

Google Earth image of the site of the Eastchurch landslide.

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As the Google Earth image shows, this section of coast is highly landslide-prone.  Indeed, the Isle of Sheppey is well-known for its coastal landslides in the London Clay.    However, there are two aspects of this event that are quite surprising to me.  The first is that the slide has occurred in the middle of a spell of exceptionally dry weather – indeed this has been the sunniest Spring on record and parts of the UK have recorded their driest Spring on record too.  Perhaps this slide was associated with dessication rather than high pore water pressures?  But second, the images after the landslide yesterday seem to show a great deal of water in the rear scarp of the landslide:-

Eastchurch landslide

Image showing the aftermath of the second Eastchurch landslide. Note the large volume of water. Image from Kent Live.

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It is not clear to me as to the source of this water, although it could be that the failure has ruptured a pipe?

It goes without saying that this is a devastating landslide for the occupants of the house.  In general, UK house insurance does not cover damage caused by landslides or by coastal erosion.

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On reflection 1: too good to be true?

Various news outlets report a miracle recovery of a newborn baby buried in a landslide in Northern India.  The baby appears to be thriving in hospital, but the idea that a baby could survive burial in a landslide without any protection is surprising.

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On reflection 2: 50 years after Yungay

Yesterday was the 50th anniversary of the devastating landslide at Yungay and Ranrahirca in Peru, caused by a seismically triggered landslide from Mount Huasaran.

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28 May 2020

The July 2018 Xe Nammoy hydropower complex dam failure: a new paper

The July 2018 Xe Nammoy hydropower complex dam failure: a new paper

On 23 July 2018 a saddle dam at the Xe Nammoy hydropower complex in Laos failed and breached, releasing 350 million cubic metres of water. The resultant flood inundated an area of about 46 square kilometres along the Vang Ngao River, a tributary of the Mekong River basin, causing massive damage. I featured a detailed review of that event by Richard Meehan and Douglas Hamilton in 2019.  They considered the cause of the failure:

An initial review of this failure by the first author was presented in late 2018, and was followed six months later by a review by an independent expert panel drawn by the Lao government from the International Committee on Large Dams (ICOLD). Both reviews concur in finding that the failure was caused by a foundation failure beneath one of the project saddle dams.

A paper has recently been published in the journal Geomorphology (Latrubesse et al. 2020) that also consider carefully the causes and impacts of this event.  Whilst the paper is focused mainly on modelling and understanding the flood that resulted from the breach of the dam, it also considers the failure mechanism of the dam itself.  Interestingly the authors have examined the materials from which the dam was constructed.

What is not in doubt is that heavy rainfall prior to the failure induced the breach event.  However, the dam did not overtop – indeed analysis in the paper suggests that the water was at least 15 m below the crest of the saddle dam when failure occurred.  This suggests that the problem was a structural problem within the dam or within its foundation. Latrubesse et al. (2020) provide this illustration of the aftermath of the failure at the saddle dam.  This is the clearest picture of the failure site that I have seen:-

The Xe Nammoy hydropower complex

The site of the saddle dam breach at the Xe Nammoy hydropower complex in Laos. Image from Latrubesse et al. (2020), using a drone video published at https://news.v.daum.net/v/20180803103600946?f=m.

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Note the weathered material that formed the saddle dam, sitting on top of basaltic bedrock.  Images B and C show slumping in the aftermath of the breach.

The core of the dam used weathered materials quarried locally.  The research team examined the characteristics of these materials.  They concluded that the dam materials may have had a lower clay content than the designers had anticipated, which in turn provided a higher level of permeability than had been expected.  Thus, Latrubesse et al. (2020) suggest that water penetrated into the core of the dam, driving piping and, ultimately, triggering a rotational failure in the dam itself, which then allowed the breach to occur.

This mechanism of failure is a hypothesis rather than a definitive analysis.  But of course it is interesting at this point because of the similarity in mechanism to the failure of the Edenville Dam earlier this month.

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On reflection 1: an official report on a collision between a train and a landslide in the UK in 2019

The UK Rail Accident Investigation Branch has published a report into a collision between a train and landslide debris at Corby in Northamptonshire on 13 June 2019.  Key finding:

The investigation found that the cutting slope had failed because it was not designed to cope with a large volume of water that had accumulated at its crest. Flood water had accumulated at the crest because two adjacent flood storage ponds had overfilled with water from a nearby brook.

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On reflection 2:  Coastal rockfalls in Sidmouth, Devon

The coastal cliffs of Sidmouth in Devon, in the Southwest of the UK, have undergone three significant collapses in a 24 hour period. Many parts of the UK are undergoing an exceptionally dry Spring, so the failures are generating large plumes of dust.

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Reference

Latrubesse, E.M, Park, E., Sieh, K. et al. 2020. Dam failure and a catastrophic flood in the Mekong basin (Bolaven Plateau), southern Laos 2018. Geomorphology, 352, 107221.

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27 May 2020

The aftermath of the Sanford dam failure in Michigan

The aftermath of the Sanford dam failure in Michigan

The catastrophic failure of the Edenville Dam in Michigan last week was not the only dam failure that day.  About 16 km downstream from Edenville lay the smaller Sanford Dam, which also failed. In a sense this is an understandable collapse – the dam would not have been constructed to withstand the flows associated with the failure of the Edenville Dam. It would perhaps have been surprising if the structure had withstood such an event.

Planet Labs have collected images of the aftermath of the failure of the Sanford Dam.  This is a Google Earth image, collected in November 2018, which shows the site of the dam:-

Sandford Dam

Google Earth image of the site of the Sanford Dam, collected in November 2018.

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Note that the fuse plug, designed to allow an emergency increase in flow to prevent dam failure, is clearly visible.  This is the Planet Labs high resolution SkySat image of the aftermath of the failure:-

Sandford dam breach

Planet Labs image of the aftermath of the Sanford dam breach. Image copyright of Planet Labs, used with permission.

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The terrible flood damage downstream of the breach is all too evident.  The dam itself has been almost completely removed.

Rebuilding these sites is going to be a long and expensive process.

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An early failure similar to the Edenville Dam?

Meanwhile, in the comments on my earlier posts about the Edenville Dam, Bruce Feinberg has noted the similarity with the failure of the Kelly Barnes Dam on 6 November 1977 at Toccoa in Georgia, USA.  This was another earthen dam that breached during heavy rainfall, killing 39 people.  The USGS investigated this failure, and the report is online.  The report makes shocking reading – the dam was poorly documented and in a very poor state of repair at the time of failure. Photographs from 1973 show that a slope failure in the face of the dam had already occurred. The USGS report hypothesises that the breach may have been caused by a further slope failure in the downstream face of the dam:

[Slope failure] appears to be a distinct possibility, particularly on the downstream slope when the previous slope failure is considered along with the possibility of the development of tension cracks upslope of the previous failure together with a computed factor of safety that is marginal. The long period of rain would have saturated tension cracks, if they existed, and the entire downstream slope would have become essentially saturated and even more susceptible to failure. A local downstream slope failure similar to that observed in 1973 could have caused limited breaching allowing localized overtopping. This concept would corroborate the hydraulic computations.

This proposed mechanism of failure is indeed similar to that of the Edenville Dam.

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On reflection 1: no resting place

A landslide has disturbed Vicksburg National Cemetery in Mississippi, requiring archeologists to relocate the remains of the Civil War Union soldiers.  Work will now be undertaken to stabilise the slope.

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On reflection 2: A landslide video from Colombia

A nice landslide video was captured on the Florencia – Neiva highway in Colombia:-

 

 

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26 May 2020

Punatsangchhu I: identifying ancient landslides in high mountain areas

Punatsangchhu I: identifying ancient landslides in high mountain areas

There is a new paper in the journal Scientific Reports (Dini et al. 2020, available online) about the use of InSAR to study the movement of the a large rock slope adjacent to the large Punatsangchhu-I hydroelectric plant, which has been under construction for over 11 years.  Punatsangchhu I will be a 134 m  concrete gravity dam, built to supply electricity to Bhutan and India.

The project is running late and over budget.  In 2006 the estimated cost of the project was $554 million. By July 2015 this had reached $1.74 billion.  The project was meant to be completed in November 2016, but in April 2017 this had slipped to December 2022, a delay of over six years.   BBS reported in February 2019 that the completion date had slipped to 2024; I assume that the budget has escalated as a result.

The primary cause of this delay is a landslide. In July 2013 the east-facing bank of the project site failed and displaced by more than 5 metres.  This landslide has required extensive mitigation.  However, the project suffered another major, and on this occasion fatal, landslide January 2019.

Google Earth imagery shows the extensive works underway to mitigate the east-facing slope, allowing the abutment of the dam to be completed.  The Google Earth image below shows the site in 2017.  I have placed the marker at what appears to be the crown of a slope failure, although Dini et al. (2020) suggest that it extends further up the slope:-

Punatsangchhu landslide

The site of the landslide at the Punatsangchhu I dam, via Google Earth.  The image provides the coordinates of the site.

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The paper by Dini et al. (2020) uses InSAR to monitor the movement of the east-facing slope at the Punatsangchhu I dam site.  One of the great things about InSAR is that it allows us to go back in time to look at movements that occurred 15 or more years ago.  Their findings make uncomfortable reading. First, the slope was displacing in 2007, even though construction started in 2009.  In other words, the dam appears to be located by a large, ancient creeping landslide.  Second, portions of the slope have continued to move throughout the construction period, and indeed the area of active displacements continued to expand right through to 2018, the end of the study period. The paper notes that:

Stabilisation measures currently only focus on a small portion of the slope, however, the unstable area is larger than previously evaluated. 

And third, that the site is probably a large, ancient landslide.  Dini et al. (2020) have found evidence of movement over an area of 8 km2.  They include this Google Earth image of the site:-

Punatsangchhu I landslide

The site of the landslide at the Punatsangchhu I dam, via Google Earth. Image from Dini et al. (2020)., who state that the “hatched area represents damaged rock (diagonal) and undisturbed residual soil (vertical)”. The rectangle highlights the area of the 2013 failure.

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The InSAR data in Dini et al. (2020) shows different areas of movement across this large slope, covering about 60% of the total area.  The authors include that this might be a deep seated gravitational displacement.

This tale is a classic illustration of the importance of site investigation and of understanding the behaviour of the landscape in these high mountain areas.  Loyal readers will know that I have highlighted previously that many large hydroelectric schemes in high mountain areas are not managing slopes sufficiently, with tragic and expensive consequences.  The Google Earth image below shows the upper portion of the large rock slope. The morphology here, of a steep upper section and then a more planar mid-slope, would always make me deeply suspicious about the presence of an ancient landslide, and indeed when I worked in the Himalayas back in the early 2000s that is how we mapped such sites:-

 

Punatsangchhu I

The upper portions of the site of the landslide at the Punatsangchhu I dam, via Google Earth.

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so, I’m deeply intrigued as to whether this large slope was identified as being problematic before the project started.

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On reflection 1: landslides at the 2018 tsunami in Sulawesi

The debate about the role of landslides, versus tectonic deformation, in the initiation of the 2018 Sulawesi tsunami rumbles on.  A new paper concludes that landslides probably did play a role.

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On reflection 2: A lucky escape

In Sudbury, Canada a man was rescued after spending more than 12 hours trapped in a landslide.  He has a broken arm.

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Reference

Dini, B., Manconi, A., Loew, S. et al. 2020. The Punatsangchhu-I dam landslide illuminated by InSAR multitemporal analyses. Scientific Reports 10, 8304 (2020). https://doi.org/10.1038/s41598-020-65192-w.

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22 May 2020

Edenville Dam breach: interpreting the failure

Edenville Dam breach: interpreting the failure

Many thanks to all of those who contributed to the discussion yesterday about the catastrophic Edenville Dam breach in Michigan.  I thought it would be helpful to summarise views expressed, many of which have come from experts in the field.

First, it is clear that this was not an engineered failure – in other words, it was not planned.  There was some discussion on Twitter and in the comments that this was the failure of a fuse plug – i.e. a designed failure point that would release water to prevent overtopping.  I can find no evidence that Edenville Dam had a fuse plug, and I do not think that a fuse plug failure would behave in the way shown in the video.

Planet Labs have a wonderful high resolution image of the aftermath of the failure; I wpould be surprised if a fuse plug is intended to leave this type of catastrophic breach:-

Edenville dam breach

Planet Labs image of the aftermath of the Edenville dam breach. Image copyright of Planet Labs, used with permission.

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The style of failure implies that the dam had become saturated in this area.  A key question is going to be why this happened.  One suggestion is that the water level exceeded the impermeable barrier, allowing water to flow into the structure. An alternative is that the dam was suffering from seepage prior to the floods.  The Google Earth imagery is interesting – this image is from 2018:-

Edenville dam breach

Google Earth image of the site of the Edenville dam breach.

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Is there an indication here that there was deformation in the dam? Or that works had been undertaken?  I’m not sure.  It will be interesting to see both the monitoring records for the dam and the maintenance that had been undertaken, as well as the design cross-sections.

The mechanism of failure is undoubtedly a rotational slip.  It is possible that this started as a smaller failure at the crest of the dam, which then drove a larger failure in the main face.  However, I favour the interpretation that high pore water pressures, and a loss of unsaturated conditions, through the dam volume drove the failure.  There are some indications in the video that high pore water conditions were present in the lower part of the structure.

Readers have rightly pointed out that earthfill embankment dams are not unusual and, when well designed and maintained, they are not unsafe.  This dam was completed in 1924.  However, these structures do require maintenance – would you expect a train built in 1924 to still work without extensive restoration – and they were designed for a time when rainfall levels were different.  Climate change – global heating – is driving increases in rainfall intensities and durations, meaning that the Probable Maximum Flood is increasing in very many places.

I always get howls of protest when I say that climate change is important, but it is the case. These structures, worldwide, are going to need a substantial upgrade to cope with that increase in rainfall, and that’s going to be very expensive.  In the interim we will see more failures of this type.

There is also some interesting analysis of the performance of the dam prior to failure online, using INSAR data.  It is astonishing that such an interpretation can be generated so quickly.  At present I find it hard to interpret this data though – the results seem to indicate deformation across much of the structure, and the section that failed seems to show uplift not, as I would expect, subsidence.  This needs further work, but INSAR remains an exceptionally exciting area of work for these types of investigations, and for pre-failure monitoring.

The failure of the dam is a catastrophe for people living in this area.  Planet Labs have an online gallery of high resolution images of the impacts.  The Planet Labs image below shows some of the downstream flooding for example:

Edenville dam breach

Planet Labs image of the aftermath of the Edenville dam breach. Image copyright of Planet Labs, used with permission.

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But we must not forget that the effects lie upstream as well.  There are numerous houses located around the lakes whose value will have been based upon the proximity to the water.  The failure of the dam will have a profound impact, and of course the ecology of the lakes will also have been destroyed.

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On reflection 1: my most successful blog day

The past 24 hours have been my most successful day in the 12 years of this blog, with almost 50,000 individual visits.  Thank you.

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On reflection 2: Controversy over the protection of the Great Western Railway in Devon from landslides

In Teignmouth in Devon in SW England there is controversy over plans by Network Rail to change the alignment of Isambard Kingdom-Brunel’s wonderful Great Western Railway to protect it against landslides.  The article claims that the cost of these works is £500 million.

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Reference

Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

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21 May 2020

Edenville Dam failure: the astonishing video of the collapse sequence

Edenville Dam failure: the astonishing video of the collapse sequence

Please also read my follow-up post to understand this event.

Yesterday I posted about the remarkable and devastating failure of the Edenville Dam in Michigan on Tuesday 19 May 2020. There are now heartbreaking images online showing the damage that the resulting flood has caused downstream.  Given the known weakness of the dam, this is an unacceptable situation.

From a technical perspective, the most remarkable aspect of this failure is that the sequence of events that induced the breach is caught on video.  I tweeted about this yesterday, but it turns out that the landslide that initiated the collapse was also captured, by Lynn Coleman, and posted to Youtube by MLive.  This video is astonishing:-

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As always we should crowdsource an interpretation of this sequence of events, but allow me to give an initial (and not definitive) interpretation.  At the start of the video a small amount of water is seen to have overtopped the dam:-

Edenville dam failure

A still from the video of the Edenville Dam failure, captured, by Lynn Coleman, and posted to Youtube by MLive.

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It would be tempting to surmise that this was a simple overtopping, but I don’t think that is correct.  I think the video shows that the crest of the dam has deformed and dipped, creating a depression through which water has started to flow.  In other words, the video starts with the dam wall undergoing the early stages of failure, which in turn has allowed a small amount of overtopping.

The Edenville Dam failure then develops apace.  The slope fails rapidly, initially forming a large toe bulge and there is major deformation at the crest:-

Edenville Dam failure

A still from the video of the Edenville Dam failure, captured, by Lynn Coleman, and posted to Youtube by MLive.

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The failure is rapid and mobile – the still below is only two or so seconds later.  Note the blurring of the toe of the landslide due to the rapidity of motion.  there is also a hint of some dust or vapour in this area, and above the main body of the slide, which is interesting too:-

Edenville Dam failure

A still from the video of the Edenville Dam failure, captured, by Lynn Coleman, and posted to Youtube by MLive.

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The landslide has clearly not failed through the full width of the dam as there is no sign of water pouring through.  However, it is likely to have left only a very slender thickness of dam in place.  I would hypothesise that this rapidly collapsed under the pressure of the reservoir water as a few seconds later water appears on the landslide deposit:-

Edenville Dam failure

A still from the video of the Edenville Dam failure, captured, by Lynn Coleman, and posted to Youtube by MLive.

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The full breach rapidly develops after this.

This video is going to be a classic in the teaching of geotechnical failures, but it also clarifies the events that led to the Edenville Dam failure.  It would have been simple to ascribe this to a simple overtopping event that occurred when the capacity of the spillway was exceeded.  But in reality the events are are more worrying than that – the dam appears to have undergone a slope failure; a failure of its integrity.  This should never occur, and to me it suggests that the problems at the Edenville Dam went  further than known issues with the spillway.

Comments and thoughts welcome please.  Please also read my follow-up post to understand this event.

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On reflection 1: Cyclone Amphan

Cyclone Amphan made landfall on Wednesday and is now bringing heavy rainfall to NE India and Bangladesh.  There are some early indications of landslides; we await to see the full impact, probably tomorrow or on Saturday.

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On reflection 2: landslide damage to a chairlift in Alberta

A landslide on Tuesday 19 May 2020 damaged a chairlift at Nitehawk Adventure Park, a small ski field located in Grande Prairie, Alberta.  From the images the damage is serious.

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20 May 2020

Edenville dam: a major dam collapse in Michigan

The Edenville dam collapse

The Edenville dam collapse. Image from a Youtube video posted by MLive

Edenville dam: a major dam collapse in Michigan

In Midland County, Michigan, USA a dam collapse is underway, driven by heavy rainfall.   CNBC has a good article about the ongoing accident, which is causing extensive flooding.  Unfortunately, as I write, reports are coming in that a second dam, at Sanford in the same area, has also breached.

The Edenville Dam is located at 43.813, -84.376.  MLive has excellent aerial footage of the breach, and the extensive downstream flooding:

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The town of Edenville is located about 1 km downstream of the dam:-

Edenville Dam failure

Google Earth image of the location of the Edenville Dam failure in Michigan, USA.

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At the moment the cause / mechanism of the failure is not clear.  ABC12 has a report from 2018 that the licence for the dam had been withdrawn by the Federal Energy Regulatory Commission because the structure had insufficient capacity to handle the Probable Maximum Flood.  The FERC ruling is available online, and states the following:

Of particular concern is the project’s inability to pass the Probable Maximum Flood (PMF) due to inadequate spillway capacity … Currently, spillway capacity at the Edenville Project can only pass about 50 percent of the PMF.

NBC25 reports that the designs for a remediation of the hazard were being prepared, with construction anticipated in the period 2021 to 2023.

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On reflection 1: Cyclone Amphan

Cyclone Amphan will make landfall in a few hours from now in NE India; this remains an extremely dangerous storm.  As I have noted previously, although we categorise tropical cyclones on the basis of wind strength, most of the damage is typically caused by water.  India and Bangladesh have well-established systems for evacuating people exposed to storm surge (although in the time of Corona Virus these will be tested to the maximum), but this storm is likely to cause substantial levels of inland damage from flooding and landslides.

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On reflection 2: submarine landslides in the Gulf of Mexico

New research, published in Geophysical Research Letters, has detected 85 previously unknown submarine landslides in the Gulf of Mexico.  Most of these landslides were triggered by the passage of seismic waves from distant earthquakes. The study suggests higher than anticipated levels of hazard to both underwater infrastructure and coastal communities.

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