Reflections on the International Symposium on Landslides and Emgineered Slopes

As I sit in Terminal 5 at Heathrow, enduring an interminable wait for a flight to Newcastle, I have started to reflect upon the International Symposium on Landslides and Engineered Slopes, and upon the state of landslide science in general.

First, the conference conveners should be congratulated for a well-organised meeting. The venue (the Shaanxi Guest House in Xian) was quite good, although I was quite glad that we chose to stay in town in the very welcoming Hyatt Hotel. It was great to meet up with old friends and colleagues, and to make some new friends too. Finally, the proceedings volumes are splendid - the editors have done an amazing job putting this together.

Turning now to the science. A real positive was the research presented by the delegates from China. In particular, the "China afternoon" was a great success, highlighting the range of projects being undertaken within the country, and the slope challenges associated with them. They are certainly not daunted by the complexity of the environment in which they work. I do feel that at times the research might benefit from input from experienced landslide scientists from elsewhere, and vice-versa. Hopefully this will come. In particular, at times the interpretation of the landforms might usefully benefit from some input, as might the understanding of the mechanisms of failure. The loess landslides are a case in point, in which both the interpretation of the morphology of the landslides themselves and the processes through which they have occurred would benefit from some attention.

I came away with a greater sense of unease regarding the research presented from outside China. Thinking back, I find it quite hard to think of many presentations that made me go "wow!". Often the research appears to be very focused on a single area or even a single landslide with little thought of the wider implications. Case studies are interesting and of value, but the real worth comes when the example is used to tell us something about landslides in general. A few people managed this, but in my view quite a few did not.

One thing that is clear is that a range of great data is now being collected through monitoring. The technologies for collecting such data, some of it in real time, have advanced incredibly over the last few years, providing insights into the details of landslide movement in time and space, and the controls upon it, in ways that have never been possible before. The availability of, for example, slope monitoring radar, terrestrial LIDAR, InSAR, etc is now really bearing fruit. I would like to see some more detailed analysis of the data (I think the technology is running ahead of the analysis at the moment), linked in to modelling and laboratory testing. Hopefully this is just a matter of time.

There was also a fair number of presentations on the application of models to replicate landslide processes, including both two and three dimensional simulations. There is some great work in this area as the codes and hardware become increasingly able to deal with the complexities of real systems. At times I felt a little frustrated that the outcome of the work seemed to be a demonstration that through careful tuning of the model parameters it was possible to replicate some aspect of the real system, such as the boundaries of the deposit or the estimated rate of movement of the landslide. In my view this is not enough - modelling is only useful if it helps us to understand the processes better and/or it allows us to forecast future behaviour. I am also struck by the lack of linkage between model outputs and field evidence - surely comparing the outputs of runout models with the the deposit thickness and where possible its structure is an sensible thing to do? These comparisons can be used to see if the model is really able to recreate what we see in the field, and then can be used to start to help us to understand landslide processes. Like many others, I worry that traditional field data collection is declining.

A further issue of concern is that lack of presentations on landslides in less developed countries, where many of the most serious impacts occur. There was almost nothing presented on landslides in India, Nepal, the Philippines, Indonesia, Colombia, Haiti, Pakistan, and so on. It appears that a huge range of landslide environments are not getting the research that they need, compounded of course by the costs of attendance for people from those countries. This is an issue that needs serious thought and attention.

Finally, I would like to point out a few presentations that I thought were genuinely superb. On the first day, Jordi Corominas from Barcelona gave a fantastic presentation on the linkage between pore pressures and movement rates. This showed that the relationship between the two is not simple, which provides a critical insight into the complexity of landslide systems. The most impressive keynote was that of Erik Eberhardt from UBC, who frankly never gives a bad paper. He integrated modelling and monitoring data to try to understand the movement of complex landslides. This work is right on the cutting edge and continues to impress. On the first day, Professor Zu-yu Chen presented a review of the landslide dam problems associated with the Wenchuan (Sichuan) earthquake, which was an incredibly understated description of an extraordinary achievement. Finally, Meei-Ling Lin from National Taiwan University reviewed the landslides triggered by the Chi-Chi earthquake nine years ago, highlighting the ways in which landslide problems associated with the 'quake were compounded by subsequent rainfall events. This is poorly understood, but vastly important.

So those are my impressions. I would be really interested to hear what other people who attended thought as well. Please do leave a comment!

Xian paper on landslide prediction and the Saito effect

Tomorrow (Friday) I am due to present a paper at the 10th International Symposium on Landslides and Engineered Slopes. The paper title is: "Temporal prediction in landslides – understanding the Saito effect". The power point file is below (there appears to be a fault on slideshare that is preventing this from being visible on blogger. If it is not visible below, you can get it from here):

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I will put the full written paper online next week. The Powerpoint slides are hosted on SlideShare and can be directly downloaded from here. Please acknowledge any use of the material.

International Symposium of Landslides - Wenchuan (Sichuan) earthquake landslides

This week is the 10th International Symposium on Landslides and Engineered Slopes, which is a once every four years get together. This time round it is being held in Xi'an in China, which is particularly appropriate given the recent events a few hundred kilometres to the southwest. The organisers managed to timetable a session of two keynotes and six other presentations on landslides associated withe the earthquake. The session was pretty interesting and highlighted both the amazing job that the Chinese authorities and people did in the response and recovery stage after the earthquake, not least with respect to the valley blocking landslides, and the incredible amount of information that has been collected already. For example, 15,000 landslides have been mapped, hundreds of unstable slopes have been identified and in some cases hazardd assessments have been conducted. One speaker mentioned that 700 geologists have been working on landslides in the earthquake zone - if so then this is a remarkable response that few if any other countries could match.

I don't intend to cover all aspects of the presentations, not least because there was some inevitable and understandable duplication and contradictions between them. Highlights for me included:
1. The first speaker was the conference convenor, Prof. Chen, who presented a paper on behalf of Ning Liu, who was the engineer in charge of the successful draining of Tangjiashan. The presentation made the achievement of mitigating this slide all the more notable. Interestingly, the first part of the talk was on another valley blocking landslide, Yigong, which was successfully breached by the same team in June 2000. This landslide was much bigger than Tangjiashan - 300 million cunic metres, creating a lake of about 1.5 cubic kilometres. The same team, called the hydro-police, successfully drained that lake too, although the peak discharge was c.140,000
cumecs! Thus, the team that tackled Tangjiashan had experience of undertaking similar tasks. The approach used was exactly the same - i.e. to build a small channel and then to allow the water to slowly excavate it to allow the lake to drain away. They were confident that it would be OK as there were rock fragments and boulders in the landslide mass - and they were quite right of course.

He also stated that all of the other landslide lakes have now been resolved too. If so this is an unprecedented achievement for which the authorities and individuals involved deserve high praise.

2. Yin Yuping of the China Geological Survey gave a more general overview of the landslide problems, suggesting that the key issue from a slope stability perspective was probably the very high peak ground accelerations (although unfortunately these were estimated rather than empirical data being produced). He talked at length about Beichuan. The landslide that struck the old town (near the apex of the bend) killed 1600 people, partly through burial and partly as a result of a ferocious air blast that flattened every building bar one that it struck. The other was the slide that hit the New Town and buried the Middle School. 350 children were killed. Sadly it appears that this was a slope in a known state of instability - and indeed it seems that 16 piles had been installed on the slope on 2006 to improve safety.

He suggested that 15,000 landslides had been mapped to date (this looks a little conservative to me?) and that 9,000 unstable slopes had been identified. All of the landslide dams occurred close to the fault surface trace, but one large landslide occurred >300 km from the fault!

3. Qiang Xiu presented a study of the Donghekou landslide, which had a volume of 12 million cubic metres. It inundated three villages, killing about 300 people. The pictures of the landslide were very impressive indeed, although I think it is fair to say that more work is needed to understand the landslide mechanisms.

Tomorrow includes a series of keynote lectures, a round table discussion (in which I am involved) and a series of parallel sessions, all wrapped up with a cultural evening. I will try post the highlights (excluding the cultural bit) tomorrow.