5 May 2010

EGU Day 2 – afternoon sessions on vulnerability, plus Italian landslide statistics

Posted by Dave Petley

In the afternoon of Day 2 I decided to focus more on the human / vulnerability side of natural hazards, and went to two sessions on Social Sciences in Natural Hazards Research.  First up was Katie Oven from Durham, with a number of co-authors , who talked about landslide hazards in Nepal .  Now I was the principal supervisor of this research, but I am going to write about it anyway, so forgive me but understand my bias!  Katie set out to look at some fundamental questions around the interactions between landslides and people in upland Nepal. 

Katie started with the work that we published a few years ago on the occurrence of fatal landslides, which we wrote up for Natural Hazards (paper available here), and in particular on the reasons why Nepal is suffering an increase in landslides.  The question is whether this is due to physical problems – e.g. climate change, deforestation – or human factors – e.g. population growth, urbanisation.  The key issue that underpins this is that landslide vulnerability is far less well understood than is the physical hazard.  So Katie wanted to know who is vulnerable to landslides and why are they vulnerable.   To do this she looked at the upper Bhote Kosi landslide in Nepal.  In this paper she presented three case studies, all of landslide prone communities.  She found that in recent years (the last 20-30 years or so) there has been a major migration of people from  upper hillslope communities to live by the  road.  This changes their exposure to hazard, in particular putting them into the path of high energy flows that are very capable of killing people.  It is clear that people have made a conscious decision to increase their vulnerability to landslide risk because the location decreases vulnerability to other risks – i.e. they have better access to health, education, income-generating opportunities.

So, the key thing is that there is a tendency in the science community to over-estimate the role of natural hazards compared with other risks in the lives of the vulnerable people.  Decisions might appear to be illogical viewed through only the prism of hazards, but once the range other risks are taken into consideration moving into an area of higher hazard looks entirely sensible.  This of course means that we probably need to think differently about how to manage hazards in a way that really works for people.  Unfortunately, all bets will be off when Nepal suffers the earthquake that is well overdue; that is a truly terrifying possibility, but again the risks to individuals need to be considered alongside the everyday risks that the people in this are face. 

The next talk that caught my eye was that of  Marjory Angignard and her co-author looked at now affected people perceive natural hazards.  This study came out of the Mountain Risks training network project of 17 PhD students and post-doctoral researchers across Europe, working together to try to understand differences between public and expert cultures of risk.  The study presented here compared Italian and French perceptions of risk from natural hazards, and found quite large differences not only in the hazard perception (not surprising given that the hazards are different) but also that people’s source of information differed substantively between the two, presumably representing deeper cultural differences. This means that there is no silver bullet that solves the communication problems; for each area the approach needs to be locally tailored.

Eric Lindquist and Katrina Mosher-Howe looked at natural hazard problem and solution definition in the news media, based upon a study of reporting of Tropical Storm Allison in the USA.  Alison brought  five days of rainfall from 5th to 9th June 2001, inducing 22 fatalities, 70,000 houses flooded, the death of 30,000 lab animals in a flooded basement, and $5 billlion of damage.  In particular the storm caused very serious flooding in Houston.  The study looked at 500 news articles on the event from the Houston Chronicle, examining them for variables such as cause, impact, damage, blame, solutions, manifestations of harm, etc. 

A number of things came out.  First, as expected there was a very clear exponential decay in coverage of the event over several years.  Most media attention focussed on home-owners, even though this group was not the most affected.  News articles tended to blame local government, there was little blame to developers because this is a very powerful group in Houston.

Major causes articulated the causes as being associated with physical/topographic factors and drainage problems – i.e. the hazard was seen as an external process imposed on a vulnerable population.  Lots of emphasis was placed on poor infrastructure – e.g. poor drainage, etc.  However, the solutions proposed in the articles focussed on “soft” approaches – i.e. economic, development, social, infrastructure, political changes, and suchlike.

 They then looked at what actually happened in the aftermath of the event.  Interestingly, most of the changes were associated with “hard” engineering – for example Harris County spent $750 million on improvements and the City of Houston spent $250 million.  The soft solutions were poorly resourced.  Thus, there was a mismatch between the proposed solutions and actual answers. 

Very interesting stuff, but I wonder whether that newspaper has a particular political perspective that might have influenced its coverage?

Alessandro Trigila and colleagues focussed on the impact of landslides on urban areas and infrastructure in Italy, based upon the nationwide, amusingly titled but hugely impressive IFFI project.   Some of the statistics on landslide hazards in Italy defy belief:

  • The project has documented 480,000 landslides covering 20,700 square km
  • Landslides represent 6.9% of the land mass of Italy
  • 5708 Italian municipalities are affected by landslides, representing >70% of the total number.  
  • 992,403 people are at risk, representing 1.7% of population).
  • There are 43,621 hazardous locations along the transportation network.