Proven avalanche protection - an analysis

Switzerland has repeatedly experienced extreme avalanche winters that claimed victims and caused damage, for example in 1951, 1968 and 1999. The knowledge gained from these avalanche events also brings progress in protection against this natural hazard. After the avalanche winter of 1951, for example, the focus was on shoring, and after 1968 on the development of hazard maps. After the analysis of the 1999 avalanche winter by the Institute for Snow and Avalanche Research (SLF), the focus was on improving organizational measures and the training of avalanche services, writes the Federal Office for the Environment (Bafu).

In January 2018, these new measures were put to the test for the first time since the avalanche winter of 1999: Due to heavy snowfall (locally up to more than 3 meters), the highest avalanche danger level 5 prevailed again for a good two days in January. SLF and Bafu also analyzed these events in detail (see box at the bottom).

Successful implementation of protective measures

According to the SLF and Bafu, the event analysis now available shows that between January 3 and 23, 2018, a total of 150 avalanches caused damage to buildings, traffic routes, vehicles, power lines, transport facilities, and forests or fields. In 53 avalanches, there was a clearing or search operation, it said. In contrast to the avalanche winter of 1999 (17 fatalities), there were no fatalities in settlements or in protected areas, according to the SLF and Bafu. However, there were isolated avalanches in areas with avalanche barriers. This shows that there is no absolute protection against this natural hazard.

The analysis shows that integral avalanche protection in Switzerland is functioning at a high level. The additional measures taken since the avalanche winter of 1999 have been effective. In particular, these are:

• Strengthening of national and regional avalanche warning: publication of an avalanche bulletin twice a day in four languages
• Training of security officers: Courses in two levels and three languages
• Expansion of measurement networks: Number of automatic measuring stations almost doubled to a good 170. More data allows more precise forecasts.

Future challenges

In order to be able to cope with future exceptional avalanche situations, the high standard of avalanche protection in Switzerland must be maintained by all those involved - the federal government, cantons, municipalities and local avalanche services. According to Bafu, SLF and the cantons, the measures taken after the avalanche winter of 1999 must therefore be continued, including financing. Continuous maintenance of avalanche barriers and systematic care of the protection forest are also indispensable. The increased demands on safety (desired higher availability of connections on roads and railways, of ski areas; lower acceptance of closures and evacuations) would require overall a further professionalization of the local avalanche services.

The handling of sliding snow avalanches, which are increasingly being reported, poses a great challenge to the avalanche services. In the case of these avalanches, which increasingly occur in late winter (from the end of February), it is particularly difficult to predict the location and timing. Research into the causes and temporal development of sliding snow should be intensified, emphasize SLF and Bafu. The influence of climate change on future avalanche activity should also be studied in more detail, according to the analysis.

Source: SLF and Bafu

Exceptional avalanche situations and climate warming

During the heavy snowfalls in January 2018, it rained repeatedly up to high altitudes due to relatively high temperatures. The high zero degree limit and the rain up to high altitudes could lead to the conclusion that these phenomena are related to climate warming, as SLF and Bafu write. But from an isolated event like the avalanche situation in January 2018, no connection to climate change can be made, they say. Also in February 1999, the snow line had temporarily risen to over 2000 meters above sea level on February 19/20.
In January 2019, on the other hand, temperatures were consistently low during the recent heavy snowfalls. Comparing the situations of 2018 and 2019, it is clear that the temperature at lower elevations had a major influence on the flow behavior and runout of avalanches: while in January 2018 most avalanches were wet in the runout, in 2019 there were many dust avalanches. Some of them caused damage to forests.
At present, it is not clear how the predicted warming of the climate and the slightly changed precipitation regime (more precipitation in winter, at low altitudes more as rain than as snow) could affect avalanche activity, especially in large snowfall situations. Therefore, the current risk management will be continued for the time being.