An expert's view...

Professor Dave Petley, BSc (Hons) AKC PhD FRGS FGS ILTM CGeog

Dr Petley, of Durham University, UK is a world authority on landslides (refer STH blog of 08May08) and is one of the resource persons speaking in the First World Landslide Forum to be held in Tokyo, Japan on 18-21Nov2008 (his topic: Risk Management Strategies in Urban Areas) .

STH has been in touch with him for some time now and I emailed him some queries a few days ago. I reproduce my letter to him and his reply below:-
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My letter :-

dave,

some basic doubts, as and when u have the time:-

a) in the year of so that landslides have obsessed me i have found that, in india and maybe the world over this hazard, is the least known (and maybe understood). in the conference that i attended in calcutta on 16jul, this was told to me in as many words, despite the fact that in darjeeling district and sikkim we have one of the highest incidences of landslides in the world. most disaster management websites focus almost totally on floods/droughts/tsunamis/ earthquakes with landslides only being mentioned, IF at all.

what can be done to correct this?
(maybe as a direct consequence to this there is very little if any preventive work taking place against landslides.)

b) my experience over the past year has been that

i) huge landslides are not necessarily the ones causing damage and death. by and large people have already vacated such areas and whilst they may be of geological interest but they are not the ones which are killing people.

ii) it is the smaller ones, esp those creeping into our urban areas which we have to watch out for, these are anthropogenic in nature and are the killers.

having said this, i feel raising awareness amongst people, correcting drainage patterns, planting trees etc maybe more beneficial than massive geological LHZ studies and so on.

may i have yr comments?

regards

praful

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His reply:-

Dear Praful,

Thanks for your email. I am sorry that it has taken so long to get back to you - I am currently traveling to NewZealand, which is about as far as you can get from the UK. I am half way there in Singapore today.

Regarding your questions:

1. The under-investment in landslide mitigation and management, Yes, I couldn't agree more. This is somewhat frustrating as landslides cause far higher losses than volcanoes for example, and in many countries far more than earthquakes. However, earthquakes and floods tend to occur in single events that cause large numbers of fatalities, whereas landslides are incremental. This was a key reason for starting the landslide database and it is having some effect. We have a long way to go though.

2. Huge landslides vs small landslides. I do agree with you in many ways about your observations of the effects of small vs large landslides. In many cases the small landslides are the ones that have the biggest impact as people often vacate the larger ones. They also tend to be the ones that cause the poorest people to lose their homes and livelihoods, without any compensation. However, in global terms the majority of fatalities from landslides actually occur in comparably rare but incredibly destructive large events. My one caveat though is that I am quite sure that the databases misses very many small events with one or two deaths. Added together the impact of these could be large.

3. Anthropogenic landslides. Yes, I agree that these are a cause of great concern, especially in areas of rapid growth in which cities are rapidly expanding. I fear that we will see a legacy of landslides in the urban areas of Asia over the next decade as a result of the incredible rate of urbanization in Asia. Of course climate change is also a factor. The new paper in Science that demonstrates that precipitation intensities are increasing as the climate warms should be a cause of great concern to the landslide community.

Your final point, which appears to be almost a throw-away comment, is of course the most important and is very well made. There are some places in which LHZ studies are relevant - for example in Kashmir this is critically needed to identify the slopes that have been left in an unstable state. However, in most parts of the world the upshot of such studies is rarely useful. The resource would be far better spent on the things that you mention, plus proper route selection and mitigation for low cost roads, promoting soil conservation, community-led warning systems, etc. I do believe that these need to be science-led (and indeed am very frustrated by the determination of aid agencies to have no science input into their hazard management programs) though.

Landslides are a hazard that can be managed. Sadly we are failing to achieve this in most of the world. The triple whammy of climate change, population growth and land use change, without effective management strategies, mean that we losing the battle. It's a shame really.

Best wishes,

Dave

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Comments by praful rao :-

In the almost one year that STH has been in existence, what I have observed is that many landslides in our district are anthropogenic (ie we humans have caused them) and not due to geology or the wrath of nature . So complex, comprehensive and expensive studies by experts are not really required to understand the causative factors. If we are causing them, then the solution should not also be impossible - and a good starting point would be a massive awareness campaign, involving CBOs, NGOs, schools, rural SHGs and so on.

In any case, I know that, in Darjeeling district there has been no shortage of surveys carried out by geologists and experts..
The question is what happened after the surveys ?
What happened is that, the survey reports were junked in some rusty steel cupboard and have become a dusty, dog-eared relics.
The recommendations in the many survey reports never saw the light of day.

The result is minor landslips of 20years ago which could have been controlled or mitigated at a reasonable cost then have today, become veritable godzillas ripping up the landscape and which will require enormous investment to mitigate or control...
if this is possible at all...(an example of this can seen at Pashyor/ Chibo, Kalimpong).

- (the italics in Dave's letter are mine)