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Defences against avalanches

 
 
image
Artificial avalanche triggered by explosives carried out by the Serre-Chevalier (France) ski station patrol.
© Cemagref/P.BEGHIN

In 1999 a succession of exceptionally ferocious avalanches in the Alps served as a reminder of man's precarious relationship with nature. 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. A European project ('SAME') is now revealing some of the secrets behind these snowslides.

     

How can we predict and prevent avalanche risks? What scientific facts can be taken as the starting point? Some of the prevention methods used in the past - and still applied today - have shown their limitations. One example is nivo-meteorological forecasting, based on data obtained from nivology (the study of snow) and meteorology; all too often evacuations planned with this method have gone on to prove unnecessary. Avalanche maps, which attempt to combine all the spatial and spatio-?temporal data for a given site, are not much better and are of little use for forecasting.

Bridging the gaps

The EU's SAME (Snow Avalanche Modelling and Mapping in Europe) project was set up with the aim of correcting these inadequacies. It involved close international and interdisciplinary cooperation between 14 partners over a 30-month period to explore three main lines of inquiry: avalanche information systems, warning systems and modelling, and sensor testing

'These lines of inquiry reflect the areas of expertise in the research teams' explains project coordinator Gérard Brugnot, Natural Risks Delegate at Cemagref in Grenoble (France). 'Some scientists focus on measurements in the field, others on models, 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 was convinced that they had the right system. One of the merits of this project is the way it enabled us to bridge the gaps between one country and another. The exchanges between researchers were very rewarding, each one recognising the value of the others' approach.'

Data, language and models

The first stage of the project was to collect an extensive variety of data on avalanches, including site maps, incident files, procedures, etc. Once gathered, they then had to be classified and harmonised. At this stage, terminology proved a major problem. This was overcome by creating a multilingual glossary of the terms used to model and describe avalanches and to record all the relevant details.

The SAME project also made progress in the field of modelling: an inventory of about 50 different models was compiled, giving their characteristics and conditions of application. This allowed researchers to construct a single computerised platform capable of using several different avalanche models for risk forecasting.

Some of these were field-tested at five sites in France, Italy, Switzerland, Spain and Norway - each with a well-documented avalanche history. 'We can conclude that there is clearly no miracle model. Each one of them reflects certain parts of the full picture on the ground and this is why it was so interesting to be able to compare them. The researchers were able to identify the complementary elements - all of which will have to be taken into account in the future.'

Artificially triggered avalanches at specific test sites equipped with measurement instrumentation, too, have allowed better measurement and understanding of the internal dynamics of snowslides. A variety of detectors, radar instruments and sensors of all kinds were also tested at the same sites. This included precise analysis of a series of parameters and testing the effectiveness of systems for warning everyone in imminent danger.


Further research

'The accidents during the winter of 1999 were, in a way, expected. But much more precise forecasting would have been needed to avert them, and that is something we are not yet able to do,' says Gérard Brugnot. 'To make progress, we need to know more about the mechanisms that govern the build-up of 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 by experiments under controlled conditions and compared with field data provided by historians.'

With further progress in mind, the Cadzie project has been started to follow up SAME and address the new concerns raised by the February 1999 avalanches. The objective of this research, which is focusing on exceptionally catastrophic avalanches, is to improve zoning and, in parallel, make defences more effective and more reliable.

 
Title
Avalanche mapping, model validation and warning systems (SAME)

Programme
Environment and Climate (ENV 2C)

Reference
ENV4960258

Contact
Gérard Brugnot

Cemagref Grenoble
France
Fax : +33-4-76762711
E-mail
Web site

Partners
- Norwegian Geotechnical Institute, Oslo, Norway
- Laboratoire d'Instrumentation en Microinformatique et Electronique, Université de Grenoble I, Grenoble, France
- Faculté de Géologie, Université de Barcelone, Barcelone, Espagne
- Centre d'Etudes de la Neige, Centre National de Recherches météorologiques, Saint-Martin-d'Hères, France
- Forstliche Bundesversuchasanstalt, Institut für Lawinen- und Wilbachforschungf, Innnsbruck, Austria
- Instituto de Cartografia de Catalunya, Barcelone, Spain
- Ecole Polytechnolique Fédérale de Lausanne, Ecublens, Switzerland
- Space Research Institute - Russian Academy of Sciences, Moscou, Russia
- Swiss Federal Institute for Forest, Sow and Landscape, Davos, Switzerland
- Icelandic Meteorological Office, Reykjavik, Iceland
- Technische Universität Graz, Graz, Austria
- Università degli Studi di Pavia, Pavie, Italy
- Centro Sperimentale Valanghe e Difesa Idrogeologica, Arabba Belluno, Italy
- Università degli Studi di Torina, Turin, Italy

image
Simulation of the February 1999 MontRoc avalanche in the Chamonix area (calculation and image production: Mohamed Naaim).

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