Updated: European Geosciences Union Day 1

Updated to include the afternoon sessions
This week is the annual European Geosciences Union assembly in Vienna. This is the biggest annual landslide meeting - there are >300 landslide related papers this time around - and since I am the scientific secretary for the landslide session I cannot allow the opportunity to comment on what I see to pass. So here are my thoughts on Day 1. My intention is not to comment on everything that I see, but instead on those that I found interesting.

Morning sessions
The first, unfortunately poorly attended, session focused on landslides associated with loess deposits. Dr Meng and colleagues from China presented a very well illustrated overview of landslides on the loess plateau. There were some remarkable statistics - for example, in the 20th Century over 60,000 people were killed by loess landslides in China, whilst in Gansu province alone in the decade between 1875and 1985 there were over 1000 disastrous landslides, killing in total >2000 people! Interestingly, the key factor determining the spatial occurrence of landslides was the neotectonic activity - areas of active uplift have far more slides than those that are subsiding, presumably because of undercutting and oversteepening during incision. The presence of sinkholes was also shown to be rather important.

Mamyrova and her colleagues presented a paper on the investigation of the mechanics of two loess landslides in Kyrgyzstan, a place about which we here far too little from a landslide perspective. She presented some rather nice repeat pass Quickbird imagery to show the evolution of the landslides, demonstrating in particular that one of the slopes showed clear tension crack development before the main failure event. Perhaps most interestingly, the initiation of the main failure event occurred in a wet, but not exceptionally wet, year (1994). A month or so earlier there was a magnitude 3.9 earthquake just 17 km from the landslide. The authors speculated as to whether this might have played a role. This project is clearly in its early stages, but the combination of an under-reported area, a very strong research team and an aspiration to combine FLAC (finite difference) and PFC (discrete particle) modelling makes it one to watch for sure.

Later in the morning, in a far better attended session (I ended up sitting on the floor!), there was a very nice presentation by Dewez and his colleagues frim BRGM in France on the use of terrestrial laser scanning to look at coastal cliff hazards in chalk. In many ways this mirrored the work that my colleagues and I do on cliffs in NE. England and, unsurprisingly, the results were similar. Over about 1 km of cliff, and scanning from eight stations, the survey picked up 8567 individual rockfall events. The most interesting thing for me was the investigation that they had done of the role of large vs small events in erosion on the cliffs, showing that over this time a single large event contributed 85% of the volume change, and that 99.8% of the volume change comes from rockfalls that are >1 cubic metre. This is quite a different result from our observations in layered sedimentary rocks in N. Yorkshire, emphasising the role that geology plays. It should be noted though that the comparatively short duration of this study (ours is >twice as long) may mean that the results are biased by the large events that happened to occur. The authors recognised that there is a need to extend the time-base - I do really hope that this is possible as the development of long datasets is crucial if we are to understand rockfalls properly.

Travelletti and his colleagues, also from France, presented a study of the use of terrestrial laser scanning for the monitoring of a large mudslide - in this case the Super Sauze slide. In my view the application of TLS for monitoring this type of slide is too rarely presented. In this case they have used the system to look at the evolution of the steep source area and to examine the movement of the toe of the flow. Both were pretty convincing, but I was particularly impressed with the work that they had done tracing the movement of boulders to generate displacement fields. In some cases they saw 16 m of movement in a single summer, which is far greater than the c.0.25 m error in the technique at this location. This is looking like a mature technique now that really justifies more extensive use.

Afternoon
The afternoon landslide sessions focused upon geophysical techniques, many of which are a little beyond my area of expertise. I will comment on a couple of presentations though. A general point to note is that, as the chair of the session pointed out, geophysical approaches to landslide analysis have moved from being rather esoteric and obscure to generating quite a lot of interest in a very short period. This is primarily because these techniques are increasingly good at discriminating between different types of wet sediment and debris, which means that they are useful. However, I do note that the presentations that I heard were on the whole about the geophysics, and not about the landslide, so these methods are not really in the mainstream yet.

There were two presentations on the Trieve landslide complex in France, the first by Kneiss and the second by Renalier. The former focused upon the use of seismic noise to map out the subsurface geology of the slope. In particular, they used a technique that they called the H/V method to delineate the soft sediment – bedrock boundary. The story was pretty nice in that the 3D topography that they showed explains the dynamics of the movement, although it does seem to be based on a slightly simplistic view of the mechanics of the slides. Personally I would like to see some verification of the 3d model (perhaps a couple of extra boreholes to see if they can predict where the drill will meet rockhead), but overall it is a pretty nice piece of work. The second was by Florence Renalier, who was a little nervous I suspect, but did a good job (well done if she reads this). The intriguing result here was that they showed that shear wave velocity is inversely correlated with displacement rate for the landslide that they studied (in the same complex as the previous paper). That seems to me to be a pretty fundamental result, but it was not really dwelt upon. In questions the team said that they think that the shear wave velocity is related to microcrack density. I would like to hear a lot more about this to be honest.

The next paper that caught my eye was by Clara Levy and her colleagues, also from Grenoble (are they trying to corner the market in research level landslide geophysics?). This was a study of the seismic precursors to a rockfall that occurred from chalk cliffs in 2002. By luck or good design (or both) the team had a seismic network in place before the 2000 cubic metre failure occurred. It was collecting data at 30 kHz, which must be a mind boggling dataset, but what they captured was 200 seismic events in the 2 hours before the collapse. They attribute this to breaking of the remaining rock bridges (which seems reasonable). They have tried to model this effect, but have chosen to do so with a Mohr-Coulomb failure model, which is perhaps not ideal. Nonetheless, the model does show how the failure propagates through the rock bridges, with those at the toe of the slope being the last to go. The model is I think not really faithful to reality, but it is an interesting piece of work.

Finally, Arnhardt and his colleagues from Aachen decided to break up the French – Italian axis by presenting a paper looking at the use of low cost sensor networks for monitoring landslides. This is highly worthy work, but I seem to have heard numerous similar presentations, all of which come to nothing. The problem is that the low cost sensors in question are usually designed for use in nice, controlled, clean, stable environments (like in cars, high tech production lines and hospitals). Landslides are the exact opposite – wet, cold (or hot), dirty and mobile, which means that the sensors that work so well in the lab really don’t function well. This is the same issue that Pen Hadow and his friends are having in their misjudged nightmare in the high latitudes. I guess someone will crack this problem in the end – and the team from Aachen seem sufficiently serious to be the ones to do it – but I do hope that they realise just how hard it will be. I really do wish them luck and will watch their progress with interest.

Overall it has been an excellent day (thanks to all the speakers), with some great science presented. Tomorrow we have two sessions on landslide forecasting and two on landslide risk. I can’t wait!

EGU Day 4

I spent the morning in the session on the Characterization, monitoring and early warning related to large landslides. I was struck during the presentations by the degree to which the technologies for monitoring landslides have improved over the last decade or so. For example, Casagli and his colleagues gave a very polished presentation on the application of their ground-based radar LISA to the monitoring of the Ruinon landslide near to Bormio in Italy. This system, which costs about 100,000 Euros per annum to buy and operate, can produce a map of deformation with a 1 mm movement resolution at ranges of up to 1.8 km. In this case it is being used to monitor the movement of this somewhat hazardous slope failure to great effect. On the other hand, David Toll (a colleague from Engineering at Durham) presented the results of a new set of high precision tensiometers that are capable of measuring suction forces down to -2 MPa, a significant step forward for tropical soils for example. Thoeny and his collegaues introduced us to the use of dynamic fluid electric conductivity logging, which looks at changes in the electric consuductivity of saline water introduced into a deep boreholed drilled through the landslide. This technique was able to determine the locations at which water is entering and leaving the borehole, which gives a good indication of the location of, for example, the shear surface. This looks like a complex technique, but one that shows a great deal of promise once fully developed. The problem would seem to be the rather cumbersome and specialised processes involved in saturating the hole with saline water. I will watch this development with interest. Glimsdal et al. presented the results of tsunami modelling for the same slide as Thoeny, the Aknes landslide in Norway. The danger is that a large failure would trigger a tsunami that would rapidly inundate local villages. The paper introduced the initial results of modelling a potential tsunami. This is clearly work in progress, but looks interesting.

To me the key issue was highlighted by the paper of Ronchetti and colleagues, who attempted to analyse the data obtained from monitoring of a very large earthflow on Mount Modino near to Modena in Italy. They attempted to use the so-called Saito approach, which I have worked on extensively, to see whether prediction of the failure of the landslide was possible. The paper itself was interesting and there was some sign that movement could be used in this way. However, the data proved to be very noisy, such that identifying trends in real time would be an awesome challenge. This issue that this highlights is that we desperately need to develop better ways to analyse the data that wed are producing. At this meeting it has been clear that analysis is lagging well behind data production. This is surely the next challenge. I have been working with three first class PhD students - Angel Ng, Jon Carey and Chris Massey, all of whom are making really substantial progress in this area for landslide movement at least. It is clear that this is a fertile area for development and that considerable more work is needed.

In the afternoon, I attended the sessions on Rockfalls and large catastrophic landslides. This was a bizarre session in that the quality of the science presented was exceptionally variable. I won't go into detail regarding the weaker end of the spectrum. At the strong end, I was taken by a couple of presentations in particular. Pichler and his colleagues presented a very comprehensive and detailed analysis of the threat to hydrocarbon pipelines associated with rockfalls. This included dropping large boulders 20 m from a crane onto a gravel pit to see what happened, wich looked great fun at least! The result of the subsequent analysis was a clear demonstration that a 3 m thick layer of gravel placed over the pipeline is enoough to protect it against a 10 tonne boulder falling from 100 m, which would seem to be a rather valuable thing to know! Meanwhile Sausgruber presented a great paper on a massive (1.3 cubic km) ancient kink band landslide in Austria. This slide has in the past moved about 60 m, but the computer model of the slides showed that development of flexural toppling has mobilised shear strength between the beds, which has effectively stabilised the slide. Waldmann and his colleagues reported attempts to model the potential generation of a landslide induced tsunami in Nordfjord in Norway, based upon the development of failure scenarios plus an analysis of two earlier events, one in 1905 (which killed 61 people) and one in 1936, which killed 74 people. Historic photos suggest that the earlier events had a run up height of up to 33 m, illustrating the threat posed. Again, this is work in progress, but it is a very nice piece of research. Finally, Agliardi and his colleagues have untaken the massive task of mapping deep seated gravitation slope deformations (these are massive creeping slope failures that occur in high mountain areas). The study is notable because:
1. It has made use of Google Earth as a primary data source, which shows waht a fantastic resource this has now becaome;
2. The task is epic - it took the individual concerned 2 months to do the mapping alone, which must have been somewhat tiresome;
3. The statistical analysis of the results show very nicely that these types of failure represent a part of the spectrum of mass movement types, and are not a seperate class of landslide in their own right.
Again, there is probably more to do here, but the study is really valuable and needs to be continued.

All-in-all a most interesting day. Once again I was struck by the tremendous range of material presented and by the very high quality of the science in general.

EGU day 2

Day 2 of EGU had less of interest to me than Day 1. I started out in the Historical Landslides session, in which my paper was the first. Most of the other five presentations were excellent. Notable amongst these was a paper by Jan Klimes and his colleagues on the landslide threat to Macchu Micchu. In recent years there have been some fairly lurid headlines about the threat to Machu Picchu as a result of landslide activity. An example is this from the BBC in 2001:

Machu Picchu 'in danger of collapse
Geologists have warned that the ancient Inca fortress of Machu Picchu in Peru is in danger of being destroyed by a landslide...Now, geologists from the Disaster Prevention Research Institute at Kyoto University have warned that the site may be in danger of collapsing.They have found that the land is sliding down at a rate of about one centimetre (0.4 inches) a month. Scientists say this is quite fast and is a precursor to a major landslide.

Pretty scary stuff, especially the part that says that this is a prfecursor to a major landslide. Klimes made a very measured presentation in which he first showed that this is an area with a large number of neotectonic features - which means that care is needed in the interpretation of features in the landscape. He then presented the results of high quality monitoring of the movement of the deep-seated landslides at Machu Picchu. The data clearly showed that the level of movement was orders of magnitude than that suggested above - in fact no more than 2 mm per year (and often less than that). He concluded that these are probably surface movements and that there is no evidence of movement of deep-seated landslides as has been suggested before. It should be noted that the teams monitoring has used more than one tried and tested technique over a prolonged period.

The team deserve great credit for taking on this task and for showing that the threat at Machu Picchu is massively over-stated. One can only hope that the other teams that have been dedicating so much resource to this issue now focus their attention on the real problem in Peru, which is the multiple active landslides that regularly kill and injure the poor population. Addressing these slides could actually make a difference.

In another presentation, Cees Van Westen from ITC showed the sort of thing that is needed. He
presented the work of his team in trying to assess landslide hazard in Guantanamo Province of Cuba. The approach used was to assess the runout of a (very) large landslide from 1963, and to use the parameters derived in a model to assess the likely runout, and thus the risk, associated with other landslides from the same ridge. The study was very impressive and detailed. The approach is not problem-free, but represents one of the most credible attempts to do this sort of thing that I have seen.

Later on I attended talks in the session focussed on the use laser scanning and DEM analysis for the evaluation of slopes. Laser-generated DEMs are probably the biggest single advance ion landslide studies in the last decade. A few years ago when my colleagues Nick Rosser and Mike Lim presented the results of their work using this technique there was a sort of stunned amazement. Now almost everyone uses it. However, I was slightly dispirited by the simplicity of the analyses being generated. In most cases the output seemed to be little more than slope maps and displacement records. The beauty of laser scanning is that we know that the structural and movement data that it can generate tells is a huge amount about what is happening inside the slope itself. It is in many ways like an X-ray of a broken bone, and a similar level of analysis and interpretation is needed. These techniques tell us about mechanisms and processes, and there is an urgent need to look at the data properly.

Tomorrow I won't be at the conference as I have to attend an editorial board meeting, so my next post will be on Thursday.

EGU day 1

Over the next few days I will try to write up some comments on issues that arise at the landslides sessions at the European Geosciences Union (EGU) meeting in Vienna. EGU is a massive meeting (c. 10,000 earth scientists), and the natural hazards section is one of the largest. The landslide field is the biggest component of natural hazards, so there is usually something for everyone. In total there are about 240 talks in the landslides sessions, so I clearly won’t comment on them all! I will instead focus on the matters that arise that interest me in a purely selfish way.

The first session on Monday was on remote sensing techniques and slope failures. Unfortunately I missed it as I was trying to track down my luggage, which once again had been lost by British Airways. Thanks to them once again - there are times when you make me so proud to be British. Oh, and by the way, if Terminal 5 is the answer to Heathrow's problems then I do have to ask what on earth the question was...

I did make it to the second session, which was on a combination of the role of vegetation on slope stability and on landslides and climate change. All six talks were of a very high standard – clear and concise, and covering a good range of material. I am intrigued by the paucity of papers on landslides and climate change, given that this is the topic of the moment. One paper that did address this issue head on, a presentation by Remaitre and colleagues looked at the impact of climate change on shallow and deep landslides in the French Alps. The results were refreshing as they indicated that projected climate changes will reduce the occurrence of slope movements due to a drop of 1-3 m in the groundwater level. Far too rarely do we hear of positive impacts of climate change, but here they are clear.

The previous paper, but Guthrie and colleagues, looked at landslide occurrence on Vancouver Island in Canada as a result of climate change. Whilst this was an interesting approach, the analysis was on the whole a bit over-simplified I think. However, the paper did very clearly highlight the ways in which logging triggers slope failures, demonstrating that clear cutting increases the occurrence of landslides by an order of magnitude or more in this steep, wet environment. The other presentations sought to try to understand why and how vegetation improves slope stability. All were highly competent, but it is clear that more work is needed given the spatial and temporal complexities involved.

All of which seems to highlight the fact that climate change is important, but land use change is much more so in the context of landslides. We should therefore be deeply alarmed by the current situation, in which concerns about climate change are driving land use changes to allow the production of biofuels. For example, felling of forest for palm oil plantations in tropical areas would seem to be deeply unwise. In addition, we are currently seeing massive increases in food and fuel prices, which is also likely to drive increased rates of forest loss.

The first session in the afternoon focussed on landslides triggered by earthquakes. A common theme emerged in terms of the role of topographic amplification in landslide triggering (this is the way in which earthquake waves interact with slopes to cause higher levels of ground shaking, which in turn triggers slope failures). Lee and colleagues presented an investigation of slope failures triggered by the 1999 Chi-Chi earthquake in Taiwan, showing that position on the slope (i.e. proximity to the crest) is the key issue in terms of triggering failure. Meunier et al presented a rather more conceptual analysis that agreed with this, although the topographic role was less strong than some maintain. The latter seems to be let down by the use of the full length of a landslide feature – presumably including the deposit - when really only the source zone should be used. This inevitably biases the results towards the foot of the slope. The observation that slope failures might be more likely on slopes orientated away from the epicentre is interesting, but is not supported by all earthquake events. My own observations from Kashmir do not support their suggestion that landslides cluster around the epicentre either, so I think rather more work is needed here to make this analysis convincing.

Two other presentations in the session focussed upon landslides triggered by MW=7.9 the 15^th August 2007 earthquake in Peru. Wartman and his colleagues focussed primarily on an impressive lateral spread that has in places moved by in the order of 20 m. The surface area of this failure is several square kilometres. Joseph Wartman has pictures of some of the landslides triggered by the earthquake linked from his web site, including a narrated slide show. Hermanns and his colleagues reported on landslides triggered by the same earthquake, but raised a different but very interesting issue. This part of the Andes is littered with large, ancient landslides and rock avalanches, which occur on both the coastal bluffs and in the high mountains. Hermanns noted that this earthquake actually triggered surprisingly few large landslides – and indeed no rock avalanches. What sized event is therefore needed to trigger the landslides that observed – is does this require a different type of event (e.g. a crustal earthquake). There are no answers to this at the moment, but it is a question that needs to be investigated urgently. Dating the ancient landslides, which should be possible for the rock avalanches at least using cosmogenic techniques, would be a good start.

The final session of the day was the Union meeting on forecasting natural hazards. Fausto Guzzetti gave a masterclass on assessing landslide hazard and risk, provoking a lively round of questions. The following speaker, who was talking on a non-landslide topic, impressed me rather less, so I called it a day.

I have the rather unlucky task of starting the first session tomorrow at 8:30 am – I am not expecting a big crowd!