Avalanche winter 1999 in Switzerland

The main trigger for the high level of avalanche activity was heavy, persistent snowfall at low temperatures. Strong north-westerly winds caused extensive snowdrift accumulations, which made the situation worse, and the snowpack was only moderately stable. Between 20 and 23 February, these factors combined with a sharp rise in temperatures led to the highest level of avalanche activity of the winter.

Affected areas

For the first time since the introduction of the five-level European avalanche danger scale in 1993, the two highest levels of danger, 4 and 5 ('high' and 'very high'), were in place for an extended period in February 1999, including six days at the 'very high' level.

The entire northern flank of the Alps, as well as large parts of Valais and Graubünden, were hit hard. Switzerland saw numerous avalanches, mostly in the Mattertal and Lötschental valleys, Goms, Haslital, Glarus and Uri as well as the Klosters/Davos area as far as Zernez. The two biggest and highest-profile avalanche incidents, at Evolène and at Galtür in Austria, coincided with the most intense period of avalanche activity.

Evolène (canton of Valais): 21 February 1999, 12 dead, 13 buried, high level of property damage

Eight houses, four chalets, five barns and several alpine huts were completely destroyed. Seven chalets were severely damaged, while two houses and a chalet sustained minor damage. Telephone and power lines were torn down and at least nine cars were destroyed. Forests were damaged and the roads between La Sage and Villa and Evolène and Les Haudères were completely buried in a number of places. In the three avalanche paths of Le Bréquet, Torrent des Maures and Mayens de Cotter, a number of avalanches began at 8.30 pm on the Sunday evening. The starting zones were located on steep, mostly south-west facing slopes below the ridge linking Sasseneire (3253 m above sea level) and Pointe du Tsaté (3077 m).

The Evolène avalanche gave rise to protracted criminal proceedings. After more than seven years, the convictions of the mayor of Evolène and the safety chief for multiple homicide through negligence and disruption of public traffic were finally upheld by the Federal Supreme Court on 30 August 2006.

Of all the avalanches that have taken place in Switzerland in the 20th and 21st centuries, only the one at Reckingen (Goms) in 1970 and those at Vals in 1951 were more deadly, with 30 and 19 fatalities respectively.

Galtür and Valzur (Austria): 23-24 February 1999, 38 dead, over 100 buried, very high level of property damage

Two days later, a devastating avalanche took place at Galtür, in the Paznaun Valley in Tyrol, just a few kilometres from the Swiss border. The avalanche hit the district of Winkl with great force, killing 31 people in all. The next day, an avalanche struck the hamlet of Valzur, further to the east, and claimed another seven lives.

An avalanche had previously occurred at Montroc near Chamonix, France, on 9 February 1999, during the second avalanche period. Twelve people died in that incident. 

Learning lessons

Just a month after the event, the SLF, at the request of the Federal Office for the Environment (FOEN), began a comprehensive investigation in order to learn lessons from that devastating winter. It presented its analysis, Der Lawinenwinter 1999 (Avalanche winter 1999), in early 2000. 

In the study, SLF experts examined in detail the weather, snow and avalanche situation, personal accidents, damage to property, the impact of avalanche barriers and protection forests, the accuracy of hazard maps and the handling of the event by avalanche services and senior municipal and cantonal officials. At the same time, the FOEN published a pamphlet entitled Leben mit dem Lawinenrisiko (Living with avalanche risk). Both publications gave a positive assessment of the current situation, but the following optimisation measures were proposed:

Introduce an Intercantonal Early Warning and Crisis Information System (IFKIS): Road closures and evacuations can only be initiated in good time if observations on the ground are reliable and appropriate warnings reach the relevant crisis teams and avalanche services early enough. The Intercantonal Early Warning and Crisis Information System (IFKIS) was introduced in 2002, improving the flow of information between the approximately 200 SLF observers and the SLF on the weather and avalanche situation in Switzerland. The measurement and model data available to avalanche services were enhanced. In addition, the number of Intercantonal Measurement and Information System (IMIS) stations has almost doubled compared with 1999, helping to plug gaps in the measuring network.

Since 2010, the dissemination of meteorological data via the Common Information Platform for Natural Hazards (GIN) has been expanded. GIN was developed in the wake of flooding in 2005.

Standardise training: Disparities in the organisation and training of avalanche services were found to be a weak spot in crisis management. The SLF therefore joined forces with the FOEN to develop a training programme for local and regional avalanche services, within the context of IFKIS. Created from scratch, these courses have been attended by well over 1000 people since they were first introduced in December 2000. The SLF training courses for safety officers are available at two levels and in three languages.

To improve the organisation and work of the avalanche services, a set of standardised specifications was drawn up and a practical guide entitled Arbeit im Lawinendienst was rolled out in 2007, illustrating the basic requirements involved in the work of an avalanche service.

Improve avalanche warnings: The avalanche warning system has been strengthened, both nationally and regionally. Avalanche bulletins are now published twice a day in four languages online and on the White Risk app and disseminated in the media, meaning that the public are also better informed.

Increase artificial avalanche release: Since 1999, permanent explosive delivery systems have been installed in many places to protect transport routes and settlements. These have proved a cost-effective way to enhance protection of the transport network and reduce closure times. Around 10 times more are now in use compared with 1999.

Adapt protection structures: Following the extreme winter of 1951, substantial investments had been made in structural avalanche protection such as snow retention structures in starting zones, diverting structures, dams and snow sheds. These measures had been largely successful, but many were pushed to their operational limits. The avalanche control guidelines were therefore overhauled, taking into account the extreme snow depths experienced in 1999.

PLANAT's Natural Hazards Strategy for Switzerland: Despite an array of investments in Alpine areas, the extreme winter of 1999 showed yet again that natural hazards can never be prevented entirely. The National Platform for Natural Hazards (PLANAT) is an advisory committee to the Federal Council established in 1997. In 2004, it developed and published the Strategy on Protection against Natural Hazards in Switzerland, in response to a motion by former Councillor of States Hans Danioth. The strategy called for a comparable level of safety for all natural hazards and a reduction in the risks posed by natural hazards according to economic, ecological and social criteria.

RAMMS modelling software: These days, research and software modelling are instrumental to our understanding of natural hazards and their processes. Back in 1999, the SLF introduced the modelling software AVAL-1D into its practical work and since 2010 it has been developing the two-dimensional simulation model RAMMS (Rapid Mass Movements). This software calculates parameters such as avalanche runout distance, flow velocity and compression forces, providing engineers and practitioners with the data they need to determine danger regions and design protective measures.

Conclusion

In the wake of previous extreme winters in 1951 and 1968, efforts to learn lessons and make improvements for the future focused on technical structures (1951) and the development of hazard maps (1968). After the extreme winter of 1999, the emphasis was on improving and standardising organisational measures and on the training of avalanche services.

These measures have proved effective, as shown by the SLF's analysis of events in 2018, commissioned by the FOEN. That year, heavy snowfall occurred from 15 January, and more intensively from 21 to 23 January, with over 3 m falling in some places. The highest danger level 5 ('very high') was in force for two days. While the winter of 2017/18 was nowhere near as extreme as 1999 in terms of destructive potential and quantity of snow, it was nonetheless an important test and showed that the measures implemented after 1999 are having the desired effect. Nevertheless, there is no such thing as absolute safety. Even today, neither the exact location nor the exact time of an individual avalanche can be predicted.

The 2018 event analysis, including detailed results, will be published in the spring of 2019, together with a joint press release by the FOEN and SLF.