2 February 2017
Demi Lovato has her house red tagged after a landslide in Hollywood
Demi Lovato is, according to Wikipedia, an American singer, song writer and actress. She has recently spent $8.3 million on a rather beautiful house in the Laurel Canyon area of Hollywood Hills:-
It is without doubt a beautiful property, although I am slightly surprised at house close it seems to have been built to a steep slope. On Monday night, in a rainstorm, that slope appears to have suffered a landslide that sent debris into the backyard of a house alongside that of Demi Lovato. The LA Times has a photograph of the event:-
This is not a large or serious landslide by any means, but it undoubtedly raises questions about that slope. The slope is being assessed by Building and Safety Assessors, meanwhile a number of houses have been red tagged whilst their safety is assessed. The image above includes the house of Demi Lovato; it is clear from this view that a part of the house is very close to the slope, although I would stress that it is not possible to ascertain from this whether there is any danger.
This appears to be the site of the landslide as shown on Google Earth:-
It is interesting to note the very extensive engineering works going on nearby, presumably to protect the slope against failure (in this case the slope appears to have been cut to create a road bench). Interestingly, this appears to be the second landslide in the last month in Laurel Canyon. At the previous one, the affected property is apparently now on sale for $200,000.
30 January 2017
A terrifying mudslide video from Arequipa in Peru
The landslide apparently killed three people – it is not clear whether the victims were in this car or elsewhere in the landslide. It is clear that a number of vehicles were caught up in the mudslide. Global News suggests that sadly this is probably the case.
This accident appears to have occurred during heavy rainfall on the Panamerican Sur Highway. The same rainfall appears to have been responsible for this riverbank erosion event that led to the loss of a hotel in the town of Lircay in Angaraes on Thursday:
The human cost of landslides in 2016
Since 2002 I have been collecting data on the human cost of landslides, allowing individual years to be analysed. This dataset underpinned my paper in 2012 that presented the annual cost of landslides in terms of lives lost (see the accompanying blog piece that I wrote at the time). Melanie and I have a new analysis for the period 2004 to 2015 in review at the moment.
The dataset for 2016 suggests that it was a bad year in terms of the number of landslides, but that the number of fatalities was not exceptional. In total I recorded 444 landslides worldwide that caused loss of life, of which just five were triggered by earthquakes. The human cost of these landslides was 2,250 people, 10 of whom died in landslides triggered by earthquakes. By comparison, in 2015 I recorded 345 fatal landslides, causing 2,376 fatalities.
The graph below shows the cumulative total through the year of the number of landslides that caused loss of life (excluding the earthquake induced events) and the number of fatalities that they caused:
I have added to the graph a simple line between the number of fatalities / landslides at the start and the end of the year to illustrate the patterns. This shows that, as usual, in terms of the number of landslides the year started slowly but accelerated through the northern hemisphere spring and summer, and then declined through the autumn and into the winter. This is the pattern that we see every year because the Asian monsoon dominates the statistics. The fatality graph is a little more unusual though, with the peak period occurring between days 120 and 150 (i.e. in May). This is earlier than in most years, and reflects a particularly active early monsoon in South Asia.
In the graph below I have compared the human cost of landslides in 2016 with that of 2015, showing both the number of landslides and the number of fatalities. 2016 data is in black and grey, 2015 in orange and yellow):-
The differences between the annual patterns are stark. Throughout the year I recorded far more landslides that caused loss of life than in 2015. Only in the first and the last two months were the rates of events (i.e. the gradient of the lines) similar. But the number of fatalities in 2016 are dominated by those events in May, which we didn’t see in 2015. However, later in the calendar year, 2015 saw very major events that caused a big ssteps in the number of fatalities. We didn’t see these events in 2016, meaning that the curve is much smoother, and the final tally was lower.
Of course we now start to worry about the human cost of landslides in 2017. The first month of the year appears to be very similar to both 2015 and 2016, but as the graph above shows, January is a poor guide to what will happen.
27 January 2017
Cromwell Gorge: earthquake-induced groundwater changes in very deep-seated landslides
Cromwell Gorge in New Zealand is the site of a series of spectacular, extremely deep-seated landslides in schist. These landslides became famous during the construction of the Clyde Dam between 1976 and 1988, when a huge programme of mitigation was enacted to ensure that they remained stable during the filling of the reservoir between 1992 and 1993. There are 17 very large landslides, all of which now have extremely low movement rates as a result of these engineering works, which include extensive drainage to draw down the groundwater level, toe buttresses and in one case a drainage blanket. The image below shows the banks of Cromwell Gorge, taken from a helicopter hovering near to the dam:-
These landslides are extremely well-monitored in every respect, providing a fantastic opportunity to understand the nature of processes occurring within them in response to external forcings. In a paper recently published in the Journal of Geophysical Research, O’Brien et al. (2016) have looked at the groundwater response in these landslides to nearby earthquakes. This work provides two really interesting insights. The first is that there is a very clear short term hydrological response to the passage of the seismic waves through the landslide body. The graph below is an excerpt of one of the figures from the paper showing the groundwater response from two piezometers located in the Nine Mile Downstream landslide. The red bars are earthquakes analysed in this study:
The authors found that the earthquakes induced substantial changes in groundwater levels, with the response being variable within the landslides (note the image above shows one response in which groundwater increases and another in which it declines). These changes were more substantial than those generated by short term rainfall events, and in many cases the changes occurred over a period of a month or so. Increased flow was also observed in the v-notch weirs that are used to monitor flow from the drainage tunnels. It appears that the earthquakes are driving short term increases in the permeability of the landslides that allows water to move between different sections of the landslide mass. These changes appear to be temporary.
But in many ways it is the other finding that is more significant. O’Brien et al. (2016) have looked at the response of the groundwater in the Cromwell Gorge to different types of earthquake forcing. The authors found that greater changes occur in earthquakes that generate high-amplitude, long-duration, broad frequency bandwidth earthquake shaking. This differential sensitivity to the nature of the earthquake is intuitively unsurprising, but really important. We observe that similar earthquake magnitudes can generate very different landslide responses; understanding why is a key issue. This paper, and the very detailed data that it describes, provides a key insight.
O’Brien, G. A., S. C. Cox, and J. Townend, 2016, Spatially and temporally systematic hydrologic changes within large geoengineered landslides, Cromwell Gorge, New Zealand, induced by multiple regional earthquakes. Journal of Geophysical Research – Solid Earth, 121, 8750–8773, doi:10.1002/2016JB013418
22 January 2017
Nanzhang County, Hubei: 12 killed as a hotel is crushed by a rockslope failure
On Friday night a major rockslope failure occurred on a steep slope behind the Mirage Hotel in the Haishishenlou holiday village, in Nanzhang County, Hubei, China. The hotel was crushed; 12 people, including the owner, were killed in the dining room. There were three survivors (whilst two of the victims died after being rescued). Xinhua reports today that the remains of all of the victims have been recovered.
Based on the above this appears to be a massive rockslope failure – reports suggest 3000 cubic metres – that has fallen directly onto the building. The reports suggest that the largest blocks were 150 tonnes, but I would suspect based on the image that this may be an underestimate.
The slope behind the hotel is interesting. Whilst the scar of the rockfall is not clear from this image – the blocks may have come from higher up the slope – the vertical discontinuities (joints) in the mass are clear both immediately behind the hotel and in the adjacent slopes. These provide a ready-made release surface for the rockfall. We would normally expect that a good site investigation would be able to determine the hazard posed by these joints, but I cannot comment on what happened here.
Interestingly, there is no suggestion of a trigger in the news reports, although the images of the rescuers do suggest that they are dressing for cold (but possibly not very cold) weather. The reports also indicate that there were real concerns about the potential for further failures on the slope.
21 January 2017
Xekaman 3 hydroelectric plant in Laos: a very major landslide in December
The Xekaman 3 hydroelectric power station in Laos is a 250 MW dam, tunnel and associated infrastructure located at 15.375N 107.407E, close to the border with Vietnam. Built between 2006 and 2010 at a cost of US$273 million, 90% of the electricity generated is exported to Vietnam. Fairly soon after completion the dam started to be plagues by landslide problems, not at the dam site but at the penstock, which it appears was constructed on an ancient landslide without adequate measures being taken to provide stability. There is a nice paper providing details of the landslide affecting the Xekaman 3 penstock online here (NB this is a PDF).
Problems appear to have started soon after the reservoir was filled, and the paper reports multiple movement events, mostly with reasonably small displacements, that caused major damage to the penstock and associated pipelines. At one location it appears that a sinkhole has opened up, and there is also a reference to a new channel being formed. The paper notes that work was ongoing to try to solve the landslide problem; in the meantime a telescopic section of pipe was installed into the pipeline to try to accommodate movement. The paper includes the photograph below of the site. Note the re-engineered walls and structures. Note also the red-roofed powerhouse at the toe of the slope – this is a key structure in the most recent event:
At 8:45 am on 16th December a major failure occurred on this slope, which has destroyed the penstock infrastructure. Radio Free Asia has a report about the landslide, which states that:
A break in a critical waterway shut down a hydro-electric dam in southern Laos and raised questions about the quality of construction at the facility that sends most of the power it generates to Vietnam. While officials said the Dec. 16 break in the Xekaman 3 facility’s penstock posed no threat to people living downstream, it marked the second breakdown in the tunnel that channels water to the power turbine, RFA’s Lao Service has learned.
“The broken portion of the pipe is about 100 meters from the power house,” said an official who spoke on condition of anonymity. “Rocks and mud flowed into the power house.”
According to the official, the damage is extensive as the power house and its equipment were inundated.
“The dam is no longer operational,” the official told RFA’s Lao Service. “Power production is stopped.”
Perhaps the most interesting element though is a photograph of the site, also in the report:
The almost completely buried building is the power house at the toe of the slope. This was clearly an exceptionally serious, and expensive, landslide.
I have written both here and in a paper about the evidence that many of the major hydroelectric schemes under construction across Asia are taking inadequate consideration of landslides. This event reinforces my view. I continue to fear that we are heading for a tragedy.
18 January 2017
The Mount Sulzer avalanches: the amazing video
Yesterday I posted details of the four Mount Sulzer avalanches in Wrangell-St. Elias National Park and Preserve in Alaska. Information about these landslides was provided by Mike Loso – he can be contacted at the following email address:- firstname.lastname@example.org . I noted that he had kindly sent to me a video of the fourth of these events, shot from the air by Luke Wassink, a National Park Service Ranger. Luke and Mike have given permission for me to make this video available via Youtube, so I have uploaded it this morning. The video, which is remarkable, should be accessible here, and I have embedded it below:
I very much appreciate the help and support of Michael and Luke in making this available. The video is remarkable, not least because of the incredible power of the flow. But note that this event was tiny compared with the two largest events. Compare the deposit in this image with the trim lines left by the earlier flows in the image below, taken from the video:
The materials involved in these Mount Sulzer avalanches is a complex mix of ice and debris. This image, taken by Mike Loso, shows the aftermath of the August 2016 event:-
This type of landslide is poorly studied because of the difficulties in obtaining good data. The video is a remarkable addition to the portfolio of information about these slides. It will now be very interesting to see if further Mount Sulzer avalanches occur in the coming summer.
Once again I would like to thanks Mike Loso and Luke Wassink of Wrangell-St. Elias National Park and Preserve in Alaska for making this material available.
17 January 2017
Mount Sulzer debris and ice avalanches
Mike Loso (contact via: email@example.com) of Wrangell-St. Elias National Park and Preserve in Alaska has kindly provided details of an amazing series of debris and ice avalanches that have descended from the flanks of Mount Sulzer in recent years. The Google Earth image below shows the location. On the left is the site of these major landslides. The next valley to the west (on the right in this image) has also suffered a glacier surge in the 2015-16 period, but that is not the focus here.
In the couple of years before summer 2015 this site appears to have suffered at least two major debris and ice avalanche events. The image below, the earliest in this sequence (from summer 2015) shows the aftermath of these flows:
A landslide deposit is very clear in the foreground, but note the removal of vegetation on the substantial hill on the inside of the bend in the river, including the creation of a clear trim line marking the edge of the flow as it crossed the topography. The very obvious deposit in the foreground, shown below, does not appear to be the major landslide that caused this trim line; this appears to be a second, smaller, event that is sitting on the sheet-like deposit of the larger first landslide:
Later in summer 2015 there was a further (the third in this sequence) very large landslide event. This appears to have run over the hill in the foreground once more, removing even more of the vegetation:
Then in summer 2016 a further slide occurred. This landslide, which happened on 13th August 2016, was observed and videoed by one of the rangers. This video is now online. The image below shows the aftermath of the landslide:
The source of these landslides is a steep glacier terminus that is clearly capable of discharges large ice-avalanches, but that also contains evidence of strongly altered, likely clay and ice-rich, unstable slopes beneath the active glacier face:
Once again the incredibly dynamic landslide environment of the mountains of Alaska is clear. Over the last three years it is become apparent that this area is the most active on Earth in terms of very large landslides. That was not expected (by me at least).
Many thanks to Mike Loso (firstname.lastname@example.org) for providing this information, and to various others for the images.
16 January 2017
Future shock – the failure to learn from the 2015 earthquake in Nepal
The Nepali Times had a large piece over the weekend entitled Future Shock, which was driven by National Earthquake day in Nepal. In an accompanying editorial, the newspaper notes the disastrous failure of Nepal to learn lessons from the earthquake, noting that:
In Kathmandu Valley, the earthquake damage convinced many that cement buildings are safer. A stronger earthquake that lasted longer would have pancaked most concrete structures on 25 April 2015. As our special report in this edition points out, scientists have warned of much more catastrophic earthquakes in the vicinity of Kathmandu Valley and in Western Nepal. Existing and new buildings are just not capable of withstanding the intensity of shaking we are bound to experience in the Central Himalaya at any time.
And, most importantly:
We do not intend to spread panic, but the sad fact is that Nepal has squandered the lessons of 2015, and we are woefully unprepared for a disaster sure to come. This doesn’t just mean rehabilitating structures that came down two years ago, but also retrofitting buildings in western Nepal where a Big One is imminent.
The delayed and ineffective response to 2015 and the lack of serious preparedness is a result of a larger failure of governance. As our report shows, the whole corrupt building permit process has to be overhauled so that safety comes before revenue. We cannot afford to wait for the politics to fix itself, our greatest concern now should be on pre-disaster preparedness and to learn from past experiences.
In my opinion, this hits the nail on the head. The earthquake left many unstable slopes, and many exceptionally vulnerable people, in the mountainous areas to the north of Kathmandu. There was an almost total lack of government-led preparedness for the 2016 monsoon, despite warnings that the situation was highly dangerous. Since then, progress has been slow, even though the 2017 monsoon is just months away. It is hard not to believe that Nepal is heading for an even greater disaster.
The full set of Future Shock articles – they are all worth a read:
- ‘Not out of danger yet’, Sonia Awale
- Stirred, not shaken, Kunda Dixit
- Cashing in on politics, Shreejana Shrestha
- A concrete future, Sonia Awale
- A month that felt like a year, Kunda Dixit
- Preparing to be prepared, Kunda Dixit
12 January 2017
Volcan, Argentina: massive mudflows cause major disruption
Heavy rainfall in the extreme northwest of Argentina, close to the border with Chile, has caused major mudflows over the last few days. Whilst the focus in the media has been on the disruption to the Dakar Rally, the impact on local people has been far more serious, especially in the town of Volcan. Two fatalities have been reported.
Reuters has a nice image of the level of destruction caused by one of the landslides, which has affected the margins of the town:
Meanwhile AP has a view from a different perspective:
The AP report indicates that there were at least two major landslides, affecting the towns of Volcan and Tumbaya, which lies a little to the north. These appear to be highly mobile mudflows in very fine-grained materials, similar to lahars. There is a major volcanic province reasonabley close to this area of the Andes, but I have not been able to ascertain whether this region consists of volcanic deposits (the name of the town is of course interesting in this respect). About 1000 people have needed to be relocated.
A quick view of the Google Earth imagery for this area suggests that these are not the first landslides to affect Volcan by any means:
There are some pretty interesting landslides in this image. The event of the last few days appears to have come down to the valley to the north of the town (on the right side in the image above). The location of the town makes it vulnerable to these high mobility flows.