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Lothar: a winter storm that changed the Swiss Plateau

On Boxing Day 20 years ago, the morning of 26 December 1999, Hurricane Lothar swept across the Swiss Plateau with windspeeds of well over 100 mph.

23.12.2019 | Mathias Kobel

The photograph shows a forest above Giswil in the canton of Obwalden destroyed by Hurricane Lothar (Photo: Reinhard Lässig, Swiss Federal Institute WSL)
A forest above Giswil in the canton of Obwalden destroyed by Hurricane Lothar, 2000 (Photo: Reinhard Lässig, Swiss Federal Institute WSL)

The storm caused enormous damage in Switzerland, France and Germany. Buildings, infrastructure and forests were badly affected. 80 people lost their lives: 14 died in Switzerland during the storm and 15 more in subsequent forest clean-up operations. The cost of the damage caused by Lothar is estimated at CHF 1.78 billion. The Library am Guisanplatz has specialist literature, newspaper articles and films on DVD on the subject.

Low air pressure, enormous temperature differences

The Lothar phenomenon, like Storm Vivian (1990), was a winter storm, with gusts of wind measured at over 140 mph. A windstorm is caused by low air pressure and enormous temperature differences between warm and cold air. Hurricane Lothar was the result of a massive area of low pressure over the North Atlantic and a frontal system spreading from the Atlantic.

Forests swept bare

Within a very short time, the hurricane swept even old forests with sturdy trees bare. In Switzerland, the Swiss Plateau, the Pre-Alps and central regions of the country were badly affected. According to a survey of cantonal forestry services carried out by the Swiss Forest Agency (now the FOEN), around 46,000 hectares of forest was destroyed, 4.3 per cent of all Swiss forest.

Buildings were also badly damaged. The cost of the damage in Switzerland amounted to CHF 600 million. Roads and railway lines were blocked by fallen trees. Half a million consumers went without electricity for a lengthy period of time due to disruptions and outages in telecommunications and electricity systems. One indirect consequence of the hurricane was a bark beetle infestation.

Military and civil defence units in action

The clean-up operations, rehabilitation of the forests, and repairs to infrastructure were carried out by forestry workers, civil defence units, the armed forces and numerous other persons and organisations. In an initial phase, timber was felled by professional foresters and then the long and costly clean-up process began.

Since 1999, new forest has grown to replace the areas destroyed by the storm. Since Vivian and Lothar, the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), the Federal Office for the Environment FOEN and other institutions have conducted several studies. The lessons learned should help to reduce the damage caused by future winter storms. For one thing is clear: major storms will continue to occur. As an aid to prevention, the FOEN has published a Storm Damage Guide. It aims to help in dealing with storm damage in forests.

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