14 November 2016
First news of landslides from the Kaikoura Earthquake sequence in New Zealand yesterday
The large sequence of earthquakes in the northeast of South Island in New Zealand, the first of which was the M=7.5 Kaikoura Earthquake (this may actually have been a pair of events), occurred in a mountainous but sparsely populated area. New Zealand is highly landslide prone at the best of times, so it is unsurprising that there are initial indications that the Hamner earthquake sequence has triggered substantial numbers of landslides.
The first images of these landslides are now starting to appear. The coastal region in the area of Kaikoura, seems to have suffered from a number of large landslides, blocking the state highway and railway line that run down the east coast. These are key lifelines linking the Cook Strait ferries that go from Picton with most of the population of the South Island, including the city of Christchurch:
There is an alternative road route, but it is a huge detour and crosses the Southern Alps in a pass. But State Highway 1 is blocked with some substantial landslides, as this image, tweeted by Marlborough Emergency, shows:
This is by no means the only landslide of this type blocking the coastal road. This image was tweeted by SkyAlert:
Whilst this landslide has caused remarkable deformation to the railway line:
I wonder also whether these images are showing vertical uplift of the land surface, based on the shoreline platform.
There also appears to have been substantial landsliding inland. One landslide is reported to have blocked temporarily the Dart River, although water is now flowing once more. This image appears to show the landslide:
There appear to be other landslides in this image as well.
This landslide appears to have left some very bemused cows:
Please post links to further images in the comments below. In the meantime I suspect that the Landslide team at GNS Science are going to be very busy for the next few months.
13 November 2016
Asakveien: a deadly quick clay landslide in Norway on Friday
On Friday I posted about a dramatic quick clay landslide in Canada at the end of last week, which fortunately did not lead to loss of life. Sadly, late on Thursday afternoon another event occurred, this time at Asakveien in Sørum municipality in Norway, with a much higher cost. Aftenposten has a detailed article about the landslide, and its consequences, in Norwegian, but Google Translate does a pretty good job (with some minor edits by me):
At 5:45 pm on Thursday afternoon, the police received police notification that a mudslide had occurred in Asakveien in Sørum municipality, near a climbing park. The landslide has a width of 400 meters and was almost 300 meters long. Six forestry workers who work on a nearby farm were in the area where the landslide occurred. Three of them escaped and reported to the police that three colleagues are missing.
It has now been accepted that the three missing men, all from Lithuania, have lost their lives, although the most recent reports suggest that their bodies have not been recovered as yet.
The newspaper images show that this is another classic quick clay landslide:
There is also some excellent drone footage on Youtube:
There are suggestions, without any real evidence as far as I am aware at this point, that the landslide might have been triggered by construction, possibly associated with the road near to the toe. This of course would not be the first case in which a quick clay landslide has been triggered in this manner. There is a very interesting still from the video below:
To the right of the landslide are both earth moving equipment and what appear to be cut slopes. It would be most interesting to know if this activity extended into the area that failed. Inference from the image above suggests that this might be the case.
Thanks to Odd Are Jensen for pointing this one out to me.
11 November 2016
St-Luc-de-Vincennes: a spectacular quick clay (?) slide in Quebec
A spectacular landslide occurred yesterday (Thursday) morning at the village of St-Luc-de-Vincennes in Quebec, Canada. Reports suggest that an area about 200 m wide was affected, and as a result several houses have had to be evacuated.
That is an impressive slide. Xania News has this less good in terms of resolution but incredibly interesting image too:
And this is the debris trail, via Mireille Roberge on Twitter:
The shape of the landslide, with the narrow outlet and large bowl, plus the high mobility of the very wet, muddy debris, suggests to me that this might be a classic quick clay landslide. It would be interesting to know whether works had been undertaken on the slope to cause destabilisation. This is a Google Earth image of the site from 2013:
There is no sign of instability in the field, but note right at the toe of the failure, where the debris has entered the stream, there is an active landslide in the imagery:
It is possible that this landslide retrogressed, and then triggered the runaway quick clay (?) landslide.
Previous posts about quick clay landslides
- Possible pre-failure ground deformation at the St-Jude quick clay landslide in Canada
- Possible flowslide (not a sinkhole) in St Jude, Canada
- Norwegian landslide – is this a quick clay slide?
- Vestfold in Norway – an unusual landslide takes out a major highway bridge
- The Rissa landslide – new (old) video available online
10 November 2016
Planet Labs satellite image of the Lamplugh Glacier landslide
The new private satellite image provider, Planet Labs, has the capacity to collect high resolution imagery to order. A few weeks ago I highlighted an image that they had collected of the giant, and somewhat bizarre, avalanches in Tibet. Earlier this week they tweeted that they have collected an image of the massive Lamplugh Glacier / Glacier Bay landslide in Alaska, which I featured back in June, with a follow up a little later. The tweet from Planet Labs stated:
Our satellites spotted this massive landslide on Alaska’s Lamplugh Glacier in August.
As a reminder, this is a very large landslide – about 10 km with a mass of around about 150 million tonnes. It occurred on 23rd June 2016 at 08:20 local time.
The image that Planet Labs have tweeted is fantastic. I have no link with them, so no nothing about the context of the collection of this data, but the image is undoubtedly worth posting:
The little wisps of dust at the head of the landslide suggest to me that there was some ongoing rockfall activity in this area when the image was collected (which is not surprising). The image beautifully captures the flow lines in the landslide – note how they deviate outwards on the margins of the landslide deposit to create the tongue structures that seem characteristic of rock avalanches flowing across ice. The interaction between the landslide and the terrain towards the top of the image is also interesting; in particular the way the landslide mass has travelled up the slope slightly to the right of centre could be used to gain an understanding of local velocity.
This is a landslide that deserves further study; I hope that someone is taking on that task.
Other posts that may be of interest:
- Glacier Bay Landslide in Alaska: a satellite image and new videos
- Lamplugh Glacier rock avalanche: A massive new landslide in Alaska on Tuesday
- The Tyndall Glacier landslide: images from the University of Alaska Fairbanks
- The Tyndall Glacier landslide in Alaska: the largest recorded non-volcanic landslide in North America
- Sitka landslide in Alaska – the potential power of simple geomorphic mapping
- Ferebee Glacier: another rock avalanche in Alaska
- Mount La Perouse: Sunday’s rock avalanche in Alaska has been found
8 November 2016
Recent increases in the retreat rate of chalk cliffs in southern England
One of the most spectacular landforms of the south of England are the famous high chalk cliffs. Perhaps best known as the sight that greets those arriving by sea to Dover, the chalk cliffs occur along the central and eastern part of the south coast, with the most spectacular examples being found in East Sussex:
These cliffs actively erode, with large rockfalls being a key mechanism. We expect that the erosion rate of these cliffs will increase as sea level rise accelerates and the climate becomes more stormy. This effect can be modeled, but to be reliable these models need to be calibrated with historical data. But, reliable data to allow past cliff positions to be ascertained extends only 200 years at best, and has large errors until modern times.
Fortunately a solution is at hand. In recent years so-called cosmogenic isotope techniques have been developed that allow surfaces to be dated – or more precisely, the point at which a surface was created can be ascertained. As chalk cliffs retreat they leave a wave-cut platform at the base (this can be partially seen in the image above). Cosmogenic isotope dating can then be used on the surface. A transect across the platform should yield the youngest dates at the cliff toe (where the platform was most recently created) and the oldest dates out towards the sea. Thus, the age profile of the platform can be determined, which in turn gives the rate of retreat of the cliffs. This sounds very straightforward, but in reality it is fiendishly difficult. The most challenging elements are that the platform itself erodes downwards after it was created, and of course it is submerged by the sea and / or a beach for much of the time. This means that to ascertain reliable dates requires complex modeling of the results, but if that can be overcome then a great deal of insight can be gained.
In a paper just published in PNAS, Hurst et al. (2016) have dated the wavecut platforms at the toes of the East Sussex chalk cliffs using a cosmogenic technique, Beryllium 10 on exposed flints that sit within the chalk. In this area, the cliffs are currently retreating at rates of 10 to 80 cm per year, some of the highest in the UK. At Beachy Head no attempt is made to reduce coastal erosion with defences, although adjacent areas of coastline are protected. Two sections were dated, one at Beachy Head and one at Hope Gap.
The headline from the study is that the erosion rate has changed drastically in recent times. If we take Beachy Head for example, the modern (i.e. post-1870) retreat rate is 22 cm per year, whilst the long term retreat rate is deduced to be 2.6 cm per year. Thus the retreat rate has increased in modern times by a factor of about ten. This is a dramatic change. Hurst et al. (2016) suggest that this is probably a result of an increase in wave energy delivered to the coast, possibly in part due to increased storminess and in part to a reduction in beach width (beaches protect the cliffs from wave action) due to coastal defences to the west, which have starved this section of coast of its supply of sediment.
The implications for the future are clear. This is a highly populated area, so infrastructure is at risk. This for example is the clifftop at Birling Gap, just along the coast to the west:
But this area is a national park, so the effects may not be very dramatic. Elsewhere thie implications of this study may be more profound.
Martin D. Hurst, Dylan H. Rood, Michael A. Ellis, Robert S. Anderson, and Uwe Dornbusch. 2016. Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain. PNAS. Published ahead of print, November 2016. doi:10.1073/pnas.1613044113
Similar posts that may be of interest:
- Remarkable coastal change from the recent UK storms
- Over a century of rockfalls on a coastal cliff at Nobbys Head, Australia
- Coastal erosion and residential property
- Coastal erosion as art
- Coastal erosion and climate change: Implications for the shoreline over the next century
- Coastal erosion – the last groyne problem
7 November 2016
The 2016 landslide year to the end of October
A couple of months ago I reviewed the impact of landslides in 2016 to date; I thought it would be timely to provide an update on the 2016 landslide year to the end of October. I will develop this further in my talk at the landslide session at AGU in December – I believe that this is a session that will be live-streamed, so those who cannot make it will be able to tune in. The data that I am using here is based on my long term (since 2002) data on landslides that cause loss of life, as described in Petley (2012) [Contact me via the blog if you want a copy]. Note that I only collect data on landslides that kill people.
The headline is that the 2016 landslide year has been a bad year in terms of numbers of events. As of the end of October I have recorded 396 non-seismic landslides. At a similar point in 2015 I had recorded 330 landslides. However, in terms of loss of life the numbers are much more average, with 2,021 deaths in total. This reflects the lack of any really large events in the 2016 landslide year to date. Of course that can still change.
This is the cumulative graph for landslide losses to date in 2016:
I have added a linear best fit line for both datasets simply to emphasise the deviation from the trend. In both cases the number of landslides is low in the first part of the year, then accelerates from about day 120. The number of recorded landslides is high through the northern hemisphere summer, but from about day 210 has settled down to a rate similar to the annual average. The number of deaths is dominated by significant loss of life around day 140. Since then the rate has been similar to the annual average.
In both cases, the high rates in the northern hemisphere summer reflect an active South Asian monsoon.
By way of comparison, this is the 2016 plotted alongside that for 2015:
The data suggest that the numbers of fatalities do not vary greatly between the two years to date. However, the number of recorded events in the 2016 landslide year greatly exceeds that of 2015, and indeed is now greater than for the entire year.
4 November 2016
The Nera River landslide triggered by the Norcia earthquake
In my post earlier today I briefly mentioned the large Nera River landslide, which blocked the Nera River near to the town of Visso. Salvatore Martino has kindly sent an update on this landslide:
The M 6.5, 30 October earthquake occurred in Central Italy triggered hundreds of landslides among which a rock slide of about 600,000 cubic metres (estimated by preliminary field surveys) along the Nera gorge (close to the Visso village) about 8 km from the epicenter. The landslide debris dammed the Nera River, generating a lake upstream. Presently the river is flowing again, by-passing the natural dam. The landslide seems to have a structural control since the detached rock block was delimited by well developed joint systems. The fallen blocks probably mobilized previously existing debris cover so increasing the volume of debris which filled the river.
Here there are some images of the landslide event collected by the CERI research team and the Google Earth view of the gorge before the landslide collapse.
These are the images:
Landslides from the Norcia earthquake sequence in Italy
The M=6.5 Norcia earthquake in Italy a few days ago is the latest in a sequence that stretches back some months. As I noted previously, Salvatore Martino from the University of Roma “Sapienza”, and his colleagues have been compiling an inventory of these landslides, which is being made available online. Unsurprisingly, and very helpfully, they have been collecting data from the Norcia earthquake as well. He has very kindly provided the following update, which I post here with his agreement:
On 26th October 2016 a strong earthquake (M 5.9 – 42.949°N 13.074°E) struck the Central Apennines (Italy) at 21.18 local time, starting a seismic sequence that is still continuing. The seismic sequence generated hundreds of aftershocks (with a magnitude up to 5.4). On 30th October another mainshock (M 6.5 at 42.84°N 13.11°E) struck the same area at 07.40 local time. This is the strongest seismic shock recorded in Central Italy since the 23rd November 1980 Irpinia earthquake. The seismic events caused severe damage to historical towns and villages at Norcia, Visso, Ussita, Castelsantangelo. Thousand of persons are now homeless and a lot of interruptions have occurred on main and secondary roads.
Since the first hours after the mainshocks the work-team of the Research Centre for the Geological Risks – CERI of the University of Rome “Sapienza” is operating in field to survey the ground effects induced by the earthquake. Up to now hundreds of disrupted landslides (sensu Keefer, 1984) have been surveyed. These events mainly include rockfalls, rockslides, roto-translational landslides and debris slides, which are distributed in a wide area up to about 25 km far from the epicenters of the two mainshocks. The surveyed data will be used to update the database (Italian acronym CEDIT) of earthquake-induced ground failures in Italy (Martino et al., 2014), managed by the CERI, which will be available at this website: http://www.ceri.uniroma1.it/index.php/web-gis/cedit/ . This has been already updated after the 24th August 2016 Amatrice earthquake.
The following pictures show some of the main ground effects surveyed to date:
Youtube also has drone footage showing the aftermath of a large landslide near Visso:
1 November 2016
Another novel way to manage rockfall hazard: blasting the slope with gunfire from a tank
A few years ago I highlighted an amazing method for managing rockfall in hazard in Norway using an enormous wrecking ball suspended from below a helicopter. I have inserted the video at the end of this post in case you have not seen it. Kerry Leith (@stress-driven) came across another amazing approach in this case in Switzerland, in which gunfire from a tank was used to trigger the failure. The video itself is on Youtube, you should be able to see it below:
The caption that goes with the video says the following:
In Oberiberg the residents are at risk of a rock fall. Since the risk that the rock could even throw in the drilling of blast holes into the valley, it was decided to make the Swiss Army to solve this problem.
After a hard fight, the Swiss soldiers who conquered the rock.
Now everyone can sleep peacefully again.
My interpretation is that the issue was with the pillar shown in the image below, which presumably was showing signs of collapse, most likely through toppling:
Ultimately the efforts are successful and the column collapses spectacularly:
I guess one can say that this worked, albeit after quite a few attempts. I suspect that it was fun too.
This is the original helicopter video:
26 October 2016
Leaving the University of East Anglia
Today is the my last working day at the University of East Anglia (UEA). I have the removal company coming in tomorrow, and by the end of the day, all being well, I’ll be in a hotel in Sheffield. I start my new post as Pro-Vice-Chancellor at the University of Sheffield and Professor in the Department of Geography on Tuesday.
Here at the University of East Anglia I have been Pro-Vice-Chancellor (Research and Enterprise), a role that I have loved. UEA is a comparatively young university, but one that is immensely popular with students and that embeds a can-do attitude to research. In the latter it is most famous for Climate Change (UEA maintains the crucial HAD-CRUT4 temperature dataset) and creative writing, but there is also great strength across the disciplines from neurological physiotherapy to the Magna Carta, dementia to competition policy, international development to leafcutter ants, and much more besides. It has been a fascinating journey.
Inevitably, there have been frustrations, and as with all posts I leave pleased with the progress that we’ve made but with a sense that I could have achieved more; that is inevitable. But it has been a great pleasure to work with the rest of the senior management team, especially the Executive Deans and their Associate Deans, and I would like to single out Helen Lewis, the Director of the Research and Enterprise Division, for the extraordinary support she and her section have provided. Helen is a phenomenon, and I hope that the University continues to appreciate her talent and dedication. I could not have done my job without her.
And of course my role needed the fantastic support provided the administrative team in the Vice-Chancellors Office, and I would especially like to single out my (now retired) wonderful PA, Jacqui Churchill.
My place is being taken by Professor Fiona Lettice for the next nine months. Fiona will do a fantastic job, and I wish her well.
Overall I have learnt so much, and I have enjoyed every minute of the role. Norwich is a wonderful city and the University of East Anglia is a great institution that is going places. At the end of the day universities are about people, and UEA has many wonderful people at all levels.