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Artificial avalanche triggered
by explosives, carried out by the Serre-Chevalier (France) ski station
patrol.
© Cemagref/B.CONSTANTIN
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On
9 January 1999 the Alps saw massive snowfalls accompanied by high winds.
Frequent and heavy snowfalls persisted through to late February, bringing
in their wake one of the worst winters for avalanches the century has seen.
The mountains took a heavy toll, leaving many victims and causing major
material damage at sites in Austria (Galtür), Switzerland (Evolène) and
France (Chamonix). The scale and frequency of the disasters resulted in
many questions being asked of the local officials responsible for deciding
land-use norms and granting planning permission, as well as the experts
responsible for providing them with the objective criteria to apply when
making their decisions.
Limited
knowledge
What are the scientific facts on which these criteria are based? Certain
disaster prevention measures used in the past - and still in force today
- have shown their limitations. One example is the nivo-meteorological
forecast, based on data obtained from nivology (the study of snow) and
meteorology, which helps in planning evacuations. This system provides
a risk index on a European scale of 1 to 5. At level 4 or 5 - depending
on the region - the authorities give the order for populations considered
to be at risk to be evacuated. But in the vast majority of cases these
evacuations prove to be unnecessary and the number of false alarms shows
just how inaccurate this kind of forecasting is.
Avalanche
maps, which attempt to gather all the spatial and spatio-temporal data
at a given site, are not much better. These historical data no doubt make
it possible to identify risk areas (i.e. areas already hit by avalanches
in the past), but they are of little value in forecasting terms, for example,
in anticipating more disastrous scenarios or identifying where the next
avalanches will occur.
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Simulation of the Mont Roc avalanche,
which occurred in February 1999 in the Chamonix area. (Calculation
and image production: Mohamed Naaim.)
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Sounding
out the mountain
The EU's SAME (Snow Avalanche Modelling and Mapping in Europe) project
was set up with the aim of correcting these inadequacies.(1)
It involved close international and interdisciplinary cooperation over
a 30-month period between 14 partners from the EU, Norway, Switzerland
and Iceland.
There were
three main areas of inquiry: avalanche information systems; warning systems;
modelling and sensor testing. "These areas of inquiry reflect the areas
of expertise in the research teams," explains the project's coordinator,
Gérard Brugnot, of the natural risks programme at Cemagref, a public agricultural
and environmental research institute in Grenoble (F). "Some scientists
place the emphasis on measurements in the field, others on models, and
others on decision-support tools."
These approaches
also reflect national differences. "That is no doubt to do with the fact
that management of this kind of natural risk is closely linked to town
and country planning, and decision support, and thus to a political perspective.
Before the SAME project, everybody believed they had the right system.
One of the merits of a European project is the way it enabled us to move
away from these national approaches. The exchanges between researchers
were very rewarding, each one recognising the value of the other's approach."
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Natural powder snow avalanche
following a snowfall in the Chamonix valley (France)
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Data,
language and models
The project's initial stage involved collecting extensive and very varied
data on avalanches, including site maps, incident files, procedures, etc.
Once gathered, they then had to be harmonised and classified. At this
stage, terminology proved a major problem. This was overcome by creating
a multilingual glossary of the terms used in modelling and describing
avalanches, and recording all related indications. The researchers now
have a "meta" information system ("information on the information available").
The SAME
project also made progress in the field of modelling. Again, data had
to be gathered and harmonised. All models are different and they each
have their own area of interest. Historical data, for example, allow us
to estimate the difference between actual and forecast damage. An inventory
of about 50 models was produced, giving their characteristics and conditions
of application. This allowed the researchers to construct a single computerised
platform on the basis of which different avalanche models could be used
in risk forecasting.
Some of
these were the subject of full-scale tests at five European sites (in
France, Italy, Switzerland, Spain and Norway) with a well-documented avalanche
history. "We can conclude that there is no miracle model. Each one of
them reflects certain aspects of the true picture on the ground, which
is why it was so interesting to be able to compare them. The researchers
were able to identify the complementary elements - all of them elements
to be taken into account in the future."
These artificially
triggered avalanches also enabled better measurement and understanding
of the internal dynamics of snow movements, and a number of instruments,
such as detectors, radars and various sensor types, were tested at these
special sites. For this, a series of parameters were precisely analysed
and tests carried out on the effectiveness of systems for warning the
individuals concerned (local authorities, local population, car and train
drivers, etc.) of imminent danger.
Where?
When? Whose fault?
The scale of devastation in the Alps, coupled with media coverage, generated
many questions, accusations and legal proceedings. Local planning officials
were often accused of being too intent on encouraging the development
of tourism; scientists and experts of offering the wrong advice and failing
to anticipate the dangers; and technicians of not being conscientious
enough in their work. "It's a complex question, with conflicting interests.
Interdisciplinary working parties could be set up in order to draft standards
based on solid scientific content, from which, for example, the precise
responsibilities of individuals in charge of risk zoning could be defined.
But our work will always be fraught with the problems of spatial and temporal
precision. Exactly Where? and When? The accidents during the winter of
1999 were, in a way, expected. But averting them would have required much
more precise forecasting, and that is something we are not yet able to
do. In order to progress, we need a better knowledge of the mechanisms
that govern the building up of the snow - wind and precipitation - instability
within the snow cover, and the flow of avalanches. The models constructed
on the basis of this knowledge could then be checked both by means of
experiments carried out under controlled conditions, and also on the basis
of early field data provided by historians."
(1)
This project, supported by the Environment and Climate programme (Fourth
Framework Programme) ended in November 1998. A summary of its results
and a CD-ROM (Avalanches: mapping, model validation and warning system
- EUR 19069) are being prepared for publication (contact: denis.peter@ec.europa.eu).
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