5 December 2013
Reports are coming in a large landslide yesterday at the town of Montescaglioso in Basilicata in Southern Italy. The BBC for example has this report, there is a nice gallery of images here, and there are a few videos of it as well:
The reports suggest that it occurred after a period of heavy rainfall. The slide appears to have caused extensive damage, including the collapse of a supermarket, but it has not caused any loss of life.
This is the area affected by the landslide as per Google Earth. The landslide is in the foreground – the large red-roofed building is the Lidl supermarket that has been destroyed, as per the screenshot at the top of this post:
Note that there is no shortage of pre-existing landslides in the above image – this is clearly a very landslide-prone area. The landslide itself appears to have affected this part of the town:
Interestingly, this area is known to be affected by a large mass movement, which is known as the “Madonna La Nova” landslide. There is a poster here (NB pdf) that described remote sensing work that has been undertaken on it, and there is at least one published paper that describes it (but which I cannot access because it is behind a paywall). My very initial interpretation would be that this is the boundary of the major landslide complex (and note that the historic town has not been built in this area):
I have also highlighted the location of the supermarket. An interesting question to ponder is why the supermarket was built at this location, given that the historic town appears to have avoided the landslide-affected area.
4 December 2013
This is part 20 of the occasional Landslides in Art series. Part 19 is here.
The piece I have chosen today is A Cannonade on the Matterhorn, 1862, by Edward Whymper (1840-1911). Whymper was an English mountaineer and author whose crowning glory was to be the first person to successfully climb the Matterhorn. The successful climb was completed on 14 July 1865 as a party of seven. Whymper had already made nine unsuccessful attempts. Unfortunately, on the way back down an inexperienced member of the climbing party, Douglas Hadow, slipped and fell to his death, dragging two others, who also died, with him.
Whymper was also an engraver of illustrations, primarily for books and periodicals. Whymper published an account of the climb, and of his many unsuccessful attempts, from which the engraving is taken. The book, which of course is now out of copyright, is available online in various formats. There is even an online version. The rockfall in the engraving occurred in 1862, and thus was during one of his unsuccessful attempts.
The rockfall in the image is described as follows:
I was near to [the tent] when all at once I heard a noise aloft, and, on looking up, perceived a stone of at least a foot cube flying straight at my head. I ducked, and scrambled under the lee side of a friendly rock, while the stone went by with a loud buzz. It was the advanced guard of a perfect storm of stones, which descended with infernal clatter down the very edge of the ridge, leaving a trail of dust behind, with a strong
smell of sulphur, that told who had sent them. The men below were on the look-out, but the stones did not come near them, and breaking away on one side went down to the Glacier du Lion.
The rockfall was also observed by Professor Tyndall, and the book includes an account of the rockfall as follows:
We had gathered up our traps, and bent to the work before us, when suddenly an explosion occurred overhead. We looked aloft and saw in mid-air a solid shot from the Matterhorn describing its proper parabola, and finally splitting into fragments as it smote one of the rocky towers in front. Down the shattered fragments came like a kind of spray, slightly wide of us, but still near enough to compel a sharp look-out. Two or three such explosions occurred, but we chose the back fin of the mountain for our track, and from this the falling stones were speedily deflected right or left.”
2 December 2013
Yesterday I reached 1000 followers on Twitter on my account @davepetley. That feels like some sort of a milestone, so just a brief note to say thanks to everyone who follows me.
Late November / early December is the start of the rainy season in parts of Indonesia, which is usually accompanied by an increase in landslides. Thus it is no surprise that various news agencies have reported that nine people were killed on Saturday in a landslide at Berastagi in North Sumatra, Indonesia. The Singapore Sunday Times has this image of the landslide:
This appears to have started as a small translational slip that entrained debris en route to the bottom of the slope. The debris train suggests that there may have been at least one house directly in the path of the slide.
21 November 2013
Context of the storm surge video
Whilst this is a landslide blog, I could not ignore the extraordinary footage that has appeared in the last few days of the Typhoon Haiyan storm surge in the Philippines. Nickson Gensis, who took this video was sheltering upstairs in a solidly built house in Hernani in Eastern Samar when the storm struck. This map shows the approximate location of Hernani relative to the track of the eye of the storm:
And this is an image (from here) of the village after the storm had passed through:
The storm surge video
This remarkable video is on Youtube and should be embedded below. The really interesting part occurs from about 40 seconds, so do stick with it:
The damage shown in the picture above can be seen in a quite different light once you have seen this video. The high levels of loss are really unsurprising, and one can only imagine the terror of those who were in the path of the storm surge. This should be compulsory viewing for those who think it is acceptable to continue to increase the temperature of, and thus the amount of kinetic energy, our atmosphere.
20 November 2013
Landslides and large dams – the presentation file and full paper from my talk at the Vajont 2013 conference
A little over a month ago I gave a talk at the Vajont 2013 conference on the topic of landslides and large dams. At the time I committed to making the Powerpoint file available online, so here it is:
The file is located on slideshare – you should be able to download the powerpoint file from there. The piece is also written up in an article for the conference paper – reference below. The paper can be accessed, for free, from the conference website. The other talks and papers can also be accessed from the conference website.
In this work I looked at the Durham Fatal Landslide Database to try to understand fatality-inducing landslides associated with large dams over the last decade. My analysis of the dataset suggested that in total there were exactly 500 deaths in 37 landslide events in the ten years between 2003 and 2012. Surprisingly, with one exception these were not landslides associated with the collapse of reservoir flanks (although interesting there was an event of this type in China earlier this year). Most of the landslides were either failures at the construction sites of large dams or at the sites of workers camps.
The most interesting aspect of this analysis though is that the geographic distribution of the landslides is surprisingly uneven. This is a map showing the location of each of the landslide events – the background image is a digital elevation model:
You will see that the landslides are incredibly concentrated in Asia, and in particular in India and China. Indeed, 16 of the landslides occurred in China and nine in India, so this is a problem that is concentrated in these areas. Whilst this level of loss is in itself tragic of course, it is important to understand why this level of loss is occurring. The key slide is I think the one below, which shows two things. The shaded area is a density map of the distribution of large dams around the world, taken from the UN Large Dam Database. The black dots represent the distribution of landslides that have killed people around the worls in the period 2004-2012. The two together suggest that until now, and with the xception of Japan (where construction standards are extremely high), we have tended not to build large dams in places where landslides kill large numbers of people:
This is now changing as a huge new wave of dams is being constructed in the Himalayas in particular, which as the slide above shows, is very highly landslide-prone. The slide below shows the distribution of planned and under-construction dams, together with the dam-related, fatality-inducing landslide events that have already in this region:
My suggestion is that we, as we build dams in areas that are much more geologically-unstable the challenge of landslides becomes much more acute. The data above suggest that the hazards are not being managed adequately. This is a stark warning for the future – with the level of dam buiding in high mountain areas likely to increase in the coming years, as the map above shows, dam-related landslides are likely to become a greater problem. We have not had a repeat of the Vajont event for 50 years; I wonder if we will e able to still say that in 50 years time. There are of course other indications that we are not managing these types of dam-related slopes very well in high mountain areas.
Petley, D. 2013. Global losses from landslides associated with dams and reservoirs. In: Genevois, R. and Prestininzi, A. (eds) International Conference on Vajont – 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide, pp 63-72.
13 November 2013
This apparently happened back in August in Floyd County in Kentucky, USA. I suspect that this is the luckiest dog in that area at least:
The good news is that the dog survived, and indeed at the end of the video very nonchalantly appears on the film, sniffing around:
So how did the dog survive when the flow appears to have been (and of course was) so violent and energetic? A freeze-frame of the moment that the slide strikes the kennel is revealing:
Because the building was away from the cliff face the landslide struck the kennel low down, and pushed it forward rather than burying it. The oblique angle of the strike meant that the kennel (and presumably the dog) was shoved out of the way of the flow. This is rather similar to the car that was struck by a flow in Shaanxi Province in China in July, about which I blogged earlier this year:
11 November 2013
One of the most dispiriting aspects of the Typhoon Haiyan disaster in the Philippines is that the high quality forecasting of the storm – it was known some days before landfall that this was a monster and that it would landfall in the area around Leyte – did not lead to a higher level of resilience to the impacts. The effects in Tacloban appear to be genuinely catastrophic. I have noted previously though that in such disasters the initial news reports tend to focus on areas that are accessible to journalists (i.e. that have a working airport, as in the case of Tacloban), whilst the real story is often in the rural areas around the city, especially in upland areas. My advice to journalists has often been to head for those areas in which there is no communication, which is usually a sign that things are bad there. It is very hard to know what is happening in the Philippines away from Tacloban City at present. In the map below I have drawn on the track of the eye of the storm (data from GDACS), and I have also marked the location of Tacloban:
It is also helpful to compare the above with the TRMM image collected by NASA just at the point of landfall. I have trimmed the original image down to cover the area shown above:
What is clear from the above image is that Haiyan will have affected a vast area across Leyte, Panay and Culion. An area of particular concern must be the upland areas of Leyte. This is the track of the eye of the storm across Leyte:
On Friday I posted an image of the landslide hazard in this area of Leyte. Again I have zoomed in on this hazard map for the area shown in the image above (note red is very high hazard, orange and yellow are medium and low hazard respectively):
What is clear is that the eye of the storm, in which the highest levels of rainfall occur, passed directly over an area of very high landslide hazard. At present I have seen no indication of the impact of the storm in these areas, and of course they were immune from the storm surge. However, it would be unsurprising if the picture in these regions is very grave, and of course the likelihood of the people here having received assistance is limited given the situation in Tacloban.
8 November 2013
As I write typhoon Haiyan is tracking across the Philippines. Jeff Masters reports that this is likely to be the most intense landfalling tropical cyclone on record; as such the damage on the areas affected is likely to be extreme. As I have noted previously, whilst it is the wind that tends to grab the attention of the media (and wind speeds of 310 km/h are clearly devastating), most of the damage is done by water, in the form of the storm surge, waves, floods and landslides. In terms of the latter, unfortunately the island of Leyte, across which the storm has just tracked, is very landslide prone. Indeed, Leyte was the location of one of the most devastating landslides in recent times, when the Guinsaugon landslide of 2006 caused 1126 deaths:
Interestingly, the Guinsaugon landslide occurred as a result of ten days of rainfall that deposited over 2,000 mm of precipitation in total. Typhoon Haiyan is also likely to bring very high rainfall totals, although the high rate of movement of the storm means that durations should hopefully be comparatively short. This is a simulation of rainfall totals along the track of the storm from NOAA:
Note that the forecast from Typhoon Haiyan is for a peak total of 52.5 inches (1300 mm). Taking Leyte alone (and that is not the only part of the Philippines to be affected by this storm), landslide hazard levels are very high. This is a rainfall induced landslide hazard map, from the National Mapping and Resource Information Agency, for Leyte:
Note in particular the very high levels of hazard on the eastern-facing slopes of the upland areas. Due to the orographic effects, these areas are likely to have received extremely high rainfall totals. It would be a surprise to me if there are not very serious landslide problems in this area. A general idea of what might be expected from Typhoon Haiyan can be gained from revisiting the typhoon Bopha / Pablo disaster, also in the Philippines, of December 2012. We may well not get a proper idea of the magnitude of the losses in the upland areas of Leyte until tomorrow; I suspect that the impacts will be very serious.
7 November 2013
I missed this story at the time, but it is worth highlighting here. Back in early August, golfers at the Matterhorn Golf Club in Taesch, Switzerland faced a slightly unusual hazard when a boulder fell from an adjacent mountain to land on one of the greens. The oobgolf.com website has the best set of images, from which these are taken:
In the comments below the article, several people are confused about how it ended up in the middle of the green. I would suspect that the boulder was both bouncing and rotating – in this case the tabular shape of the rock would create a very stable motion (a bit like a wheel bouncing down a slope). This would also be why the crater has that elongated shape, and why the boulder has bounced out of it.