26 March 2015
State of emergency in Peru
Andina, a Peruvian news agency, is reporting that Peru has declared a state of emergency over a series of landslides that have occurred in the Lurigancho-Chosica district over the last few days:
“The Government of Peru has declared a 60-day Emergency in the district of Lurigancho-Chosica, following extreme infrastructure destruction caused by severe landslides over the past hours. The emergency declaration is aimed at implementing immediate, necessary measures to respond and restore the areas affected by landslides of mud and rock. Announced by President Ollanta Humala, the initiative followed the formation of Pedregal, Carossio, Rayos de Sol, Quirio, San Antonio, California, La Trinchera, Buenos Aires, La Cantuna, Moyopampa, La Libertad and Mariscal Castilla ravines, located in the said district. According to a supreme decree, published today in the official gazette El Peruano, the adoption of such urgent measures will allow Lima and Lurigancho-Chosica Municipalities to execute response and rehabilitation actions in coordination with the National Institute for Civil Defense (Indeci) and various ministries. Actions include the restoration of basic services and reconstruction of infrastructure, and can be modified in accordance with the needs and security requirements that might arise during the execution.”
The news item is accompanied by an aerial photograph that appears to show very high levels of damage caused by a debris flow:
Telesur has a gallery of images on the ground, which includes this one:
The largest event appears to have occurred in Chosica itself, where a landslide killed at least eight people, left more missing and blocked the Central Highway. Reports as to the length of the closure of the road vary between five and 30 days (the latter sounds very pessimistic to me though), driving concerns that fruit prices will soar in Lima.
This is Google Earth image of Chosica:
This is one of the ravines named in the declaration of the State of emergency. The extreme vulnerability of the houses to debris flows is clear:
25 March 2015
The Abe Barek Landslide in Badakhshan, Afghanistan
ON 2nd May 2014 a very large landslide occurred at Abe Barek (note there are multiple spellings of this name) in Ago District, Badakhshan Province in Afghanistan. This was the worst landslide of 2014, taking the lives of up to 2700 people (although estimates vary wildly). I posted extensively about it at the time (e.g. here and here), but clearly interpretations at that point were greatly limited by the lack of information from this remote and inaccessible location. In a recent paper, Zhang et al. (2015) have undertaken what I think is the first published analysis of the landslide. They have found that, as expected, the landslide occurred in a thick deposit of loess (wind-blown silt) on a site that had previously been active. The landslide occurred in two phases about two hours apart, starting at 11 am.
Zhang et al. (2015) suggest that the key factors in the landslide were:
- A complex bedrock structure overlain by silt that had been weakened by repeated seismic events;
- A slope that had been left in an over-steepened state by previous landslides;
- A wet late winter and spring period (including a rainfall event of over 200 mm in January, with smaller rainfall episodes in the days leading up to the landslide;
- Previous landslide events that had subsequently been subject to gully erosion.
The paper says that the landslide has a vertical extent of 2400 m (top of the slope at 2700 m, foot at 300 m elevation), although this feels surprisingly high to me, and appears to be contradicted by this image from the paper:
Unfortunately the analysis does not go much further than this for understandable reasons. The remainder of the paper examines and maps the susceptibility of landslides across Badakhshan, finding that in particular on the west side of the province landslide susceptibility is quite high. Sadly this means that a repeat of this landslide is far from unlikely.
Zhang, Jianqiang; Gurung, Deo Raj; Liu, Rongkun, Murthy; Manchiraju Sri Ramachandra; Su, Fenghuan, 2015. Abe Barek landslide and landslide susceptibility assessment in Badakhshan Province, Afghanistan. Landslides. doi: http://dx.doi.org/10.1007/s10346-015-0558-5
24 March 2015
Jesus in a landslide scar
The Irish Mirror has what is probably the weirdest landslide story of the year to date – indeed this will take some beating! After a small landslide in the San Francisco area of Putumayo in Colombia a likeness of Jesus has appeared in the landslide scar. The newspaper reports that the apparition is attracting hundreds of visitors – enough to need the presence of the police to control the crowds.
This is the landslide scar:
Personally, I’m unconvinced that the image is Jesus. I suspect that actually its the legendary footballer Jurgen Klinsmann:-
Uncanny! Any other suggestions? Please send via the comments and I’ll post the best ones below.
So these are the best suggestions so far:
Tor Benjar suggests George Washington:
Gail suggests Vladimir Putin:
Via twitter, Alicia laCross suggested Groot:
Also via Twitter Cryptid suggested Zeus:
Whilst via Twitter Ed Darrell suggested Glenn Frey of the Eagles:
And finally, Chicago News Bench suggested Oprah via Twitter (somewhat harsh perhaps?):
23 March 2015
Yeager Airport slope failure
Whilst the immediate crisis appears now to have passed, the Charleston Gazette has been investigating the Yeager Airport slope failure. Today they have published a very interesting article about the landslide, focusing on the pre-failure deformation of the slope. It is well worth a read – real investigative journalism. This is the time line:
June 2013: Staff at Yeager Airport noticed cracks appearing in the EMAS at the top of the slopes (EMAS is the concrete block system designed to safely stop aircraft that have overrun the airport). S&S Engineering wrote in a report for Yeager Airport that “The joint tape used to seal the blocks was tearing and separating allowing rainfall to enter block joints. Airport personnel became concerned that the cracks in the asphalt extend under the EMAS blocks allowing the rainwater to enter the engineered fill material.”
October 2013: Triad Engineering, the designer of the structure, surveyed the site.
February 2014: Triad Engineering surveyed the site again, and found deformation over the intervening four months of one to three inches (2.5-7.6 cm). However, total movement from the as-built survey was much greater. The Charleston Gazette reports that “The southwest corner of EMAS has moved forward 1.3 feet along the projected centerline, 2.7 feet to the left and 3 feet downward”, quoting from an S&S Engineering report, which is available online.
July 2014: Triad Engineering installed 24 monitoring points. All showed movement over the next month of up to 2 inches (5 cm).
early March 2015: Triad Engineering hired Rick Valentine, an expert in geo-reinforced slopes, to help monitor the slope.
8th March 2015: Triad Engineering initiated a site investigation to evaluate the movement of the fill
10th March 2015: Settlement of the southernmost corner of the fill “became more pronounced”
11th March 2015: Yeager Airport held an emergency board meeting. The Charleston Gazette reports that ‘an engineer told the board that the chances of a catastrophic failure were “very, very slight’. However, the area of Keystone Drive at the foot of the slope was evacuated.
12th March 2015: The slope failed.
The development of a slope failure can involve a feedback loop in which initial movements of the slope open cracks that permit increased infiltration, generating higher water pressures, more movement and wider cracks, and so on. Fill slopes, which are very vulnerable to high water pressures, can be particularly problematic. So it is inevitable that questions will be asked about how this ongoing deformation was allowed to develop without more intervention. It would be very interesting to see the monitoring records for the survey points. By February 2014, a year before the collapse, quite large deformations had developed. I am surprised that this did not generate a much higher level of concern, but that its of course easy to say in retrospect.
The cause of the collapse remains unclear – I have yet to see anything to clarifies as to whether this was caused by a failure in the fill (i.e. the geosynthetic reinforcement was not up to the task?) or in the foundation. Given that this is reportedly the highest slope in the world that is reinforced with geosynthetics, there will be a great deal of interest in knowing what went wrong at Yeager Airport. The Charleston Daily Mail has a nice interview with Rick Valentine, who explains what happens next in the search to understand the Yeager Airport slope failure.
21 March 2015
Over the winter an impressive and very large landslide has developed on a key strategic highway at Markovici in Montenegro. This has destroyed the main road that links Podgorica, the capital city, to the coastal urban areas. The landslide, is described in a good news article from about a week ago, has been captured in some very nice drone footage that is on Youtube:
The landslide appears to be on this section of road, as seen on Google Earth:
The damage to the road near to Markovici is impressive – this is a still from the drone footage:
In many ways this is not an exceptional landslide – it is a classic reactivation of a translational slide, caused by heavy rainfall. The road has displaced laterally and dropped as the landslide has moved, and internal deformation of the landslide body has caused the buckling of the highway.
Similar landslides occur all over the world – this is an example from near to Bharibise in northern Nepal:
Such landslides can be mitigated with standard techniques – with enough expertise and resource they can be stabilised and the road can be reinstated. The major challenge is the cost, especially in poorer countries. In Nepal this is usually managed by having a gravel surface and non-rigid structures, such as the gabians seen in the image, Each time the road moves it is regraded using a bulldozer. This results in a very poor quality road that is slow, uncomfortable and damaging to vehicles, but at least it can be reinstated reasonably quickly on each occasion. This is far from an ideal solution, but where resources are limited it is simply pragmatic.
19 March 2015
News from Serbia is that a landslide is threatening the Klisura Monastery, a medieval place of worship. InSerbia News carried a story earlier this week about the problem:
“Following its activation, the landslide above Klisura Monastery near Arilje has now reached the foundations of this medieval holy site. Abbess Evgenija said that the monastery is under threat of being pulled down unless something is urgently done. “We are filled with fear every night and we beg the authorities for help,” she told reporters. Arilje Mayor Zoran Todorovic said that this landslide is a great problem. “We are waiting for the weather to stabilize and then we will immediately initiate works to preserve the monastery,” Todorovic told Tanjug.”
I can’t find any good images of the landslide damage, but this image from PTPC seems to show instability in close proximity to the church:
This is a Google Earth perspective view of the site of Klisura Monastery:
Klisura Monastery comprises the small cluster of buildings in the centre left of the image. In the image below I have annotated the possible landslides at this site as interpreted from the Google Earth image:
To the right (on the image) there appears to me to be a large, ancient landslide. Behind the monastery there may be another large slide, but I have much lower confidence in this one given the bedrock outcrops. However, immediately adjacent to Klisura Monastery there is an active slide, and behind the church there appears to be a dormant portion. I suspect that this has now reactivated. To work out how to save Klisura Monastery a proper mapping exercise is needed. This complex landslide setting is going to make saving site quite difficult, although it is possible that the problem is just shallow sliding in the slope supported by the retaining wall behind the church.
18 March 2015
Yeager Airport fill slope failure
Movement of the Yeager Airport fill slope failure appears to have ceased and the residents of Keystone Drive have now been allowed back to their homes. There is a great deal of interest in the causes of the landslide, which remain far from clear, and in the approach that will be taken to mitigating the slope so as to protect (and presumably rebuild) the EMAS at the end of the runway. John Boyle has been undertaking some digging into the landslide history of this site; Bill Murphy at Leeds has been kindly keeping me in the loop. Two interesting aspects have emerged. The first is on a Facebook site, which includes several interesting comments from past and present residents of Keystone Drive. Key comments include the following (I have included just the key pieces of information needed to understand the site):
Robert Harrah: “…they covered up a natural spring on that hill that we played in as kids”
Terina Joe Adkins “This isn’t the first time folks. My grandparents house went over in a mudslide on Keystone 45 years ago d… Roll forward 45 years and it’s happened again…”
Kelly Stricker Spurlock “Terina, I remember that. I was just a kid when that happened. I had a friend, Sharon Koon, who also lost a house then. Did your grandparents house sit on the side of the airport just above where the church was?”
Kelly Stricker Spurlock “Almost exact same spot for the slide then and now!”
Terina Joe Adkins “Kelly, yes my grandparents, Bud and Evelyn Hill’s house sat on the side of the airport just up from the church. Almost in the exact place this slide us. My mom, Barbara talks about The Koons.”
This is backed up by a newspaper report from Charleston Gazette on 19th March 1973. Whilst the image (and indeed the caption) have not reproduced well, the implications are clear:
Kanawha Airport was renamed Yeager Airport. This Google Earth image is from 2003, before the EMAS works:
Even allowing for the distortion of the image caused by the low quality ground model in Google Earth, it is no surprise that this slope has a history of landslides. I wonder how this was taken into account in the construction of the fill slope.
17 March 2015
Exodus: God and Kings
This is part 3 of my “Landslides in Movies” series (following Part 1 and Part 2). In 2014 the film-maker Ridley Scott released Exodus: God and Kings, an epic fantasy film that retells the biblical story of Moses as he rebels against the Egyptian Pharoah Ramses, and leads an exodus of 600,000 people from the plagues of Egypt.
A critical juncture in the movie comes when Moses is struck and buried by a mudslide during a heavy rainstorm whilst looking for his sheep. The website comingsoon.net has a short film about how this scene was shot. You should be able to see the video embedded below, or you can view it here.
The film is interesting, not least because it shows the enormous effort that needs to go into creating even a comparatively small mudslide. They actually did a pretty good job, the resulting mudslide is quite credible:-
It is also interesting to see the care that was needed to secure the safety of Christian Bale when he was buried by the mudslide. It nicely illustrates the low survival rates from these types of landslides.
16 March 2015
Yeager Airport landslide
The latest news on the Yeager Airport landslide is that movement has new ceased, although the total displacements that have accumulated are now substantially larger than they were when I posted on Friday. The landslide has now destroyed the church at the foot of the slope for example, as this Charleston Daily Mail image shows:
This Youtube video captures rather nicely a fairly early stage in the movement event. Note that a quite large displacement had developed in the rear of the landslide. The internal deformation in the landslide mass appears to have been inducing smaller, flow-type failures in the frontal portion of the landslide:
This is a really good drone film of the landslide mass, showing the destroyed church and the flooding induced by the blockage in the river channel:
This still image from the video shows the displaced mass of the landslide, which has now undergone a very substantial amount of internal deformation:
The basal surface of the landslide remains unclear, but the lack of bedrock in the image suggests that my earlier hypothesis that the Yeager Airport landslide might have been induced by failure in the underlying substrate might not be correct. The rear scarp is now very steep in weak materials, suggesting that quite urgent work is needed to protect the remainder of the overrun area of the runway. The risk of more substantial flooding has been reduced by the completion of the channel around the tow of the landslide, meaning that the risk to the remaining houses on Keystone Drive has now reduced. Unfortunately though the residents will suffer considerable disruption for many months as the mitigation of this landslide is going to be a very major task.
13 March 2015
Yeager Airport is located about 5 km east of downtown Charleston in West Virginia, USA. The airport is located on top of a hill, with steep slopes on several sides, including at the end of the main runway. In 2005 a project was initiated to increase safety at Yeager Airport by creating an over-run area at the end of the runway, including the installation of an EMAS, which is a concrete surface that is designed to bring aircraft to safe stop. In 2010 this successfully arrested an over-running regional jet:
The construction of the EMAS required that a new, large fill slope was built, retained by a reinforced slope. There is a very detailed and interesting presentation about the design and construction of the slope (NB this is a PDF); at the time this was apparently the largest reinforced slope in the United States (I’m not sure if this is still the case). This images, from the presentation, shows the completed structure at the end of the runway at Yeager Airport:
In Wednesday the Charleston Daily Mail reported that six residents had been moved out of their houses below the slope as movement of the slope had been detected in the EMAS. Yesterday this quickly developed into a very large-scale landslide. This image is from a gallery that is in a Charleston Daily Mail report from yesterday:
This is a massive, very deep-seated and rather complex failure. The scale is somewhat impressive. The failure is surprising in so much as the conditions appear to be dry, a fact that is supported by this image of the rear scarp, although as the comment below notes, there has been significant rainfall and snowmelt in recent weeks:
The slope reinforcement is clear to see in the image – the failure appears to have sliced through it. The images gives few indications as to what has gone wrong – whether this is a design failure or whether something happened at the toe of the slope to change the system. I do wonder if the rock below the reinforced slope has failed though – this might explain the interesting geometry of the collapse. Either way, this is going to be very expensive, and it will affect both the operations at Yeger Airport and the local residents for some time to come.