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Floods and landslides in 2019 – western Switzerland bears the brunt of damage

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In 2019, floods, landslides, debris flows, rockfall and rockslides caused some CHF 85 million of damage in Switzerland, making it a relatively low-damage year. The cantons of Geneva, Vaud and Neuchâtel were the hardest hit. The damage primarily resulted from flooding, overland flow and debris flows, mostly triggered by thunderstorms. Rockfalls and a debris flow each claimed two lives, while a fifth person was killed by a flood. These were the conclusions of the annual analysis of the Swiss flood and landslide damage database kept by the Federal Institute for Forest, Snow and Landscape Research (WSL).

 
 

In 2019, landslides, debris flows, floods, rockfall and rockslides resulted in some CHF 85 million of damage, just over a quarter of the inflation-adjusted arithmetic mean for the years 1972-2018 (CHF 305 million)  and less than half of the cost of damage for the previous year.  2019 thus ranks 30th within the 48-year data series.

The main meteorological triggers in 2019 were thunderstorms, which caused 91% of the damage, while persistent rain (5%) and the combination of snowmelt and rain (2%) played a minor role. The lion’s share of damage costs resulted from flooding, overland flow and debris flows (97%); rockfall (2%) and landslides (1%) caused relatively little damage.

 

Damage occurred mainly in June, hitting western Switzerland the hardest

 

Up to the end of April, damage was caused almost exclusively by rockfall and rockslides. The Axenstrasse road was affected several times over the course of the year: It was partially closed for several weeks because of rockslides and debris flows. The summer months were marked by intense thunderstorms. On 15 June, a powerful thunderstorm complex swept through Switzerland from the southwest, triggering flooding and overland flow which caused severe damage, particularly in the cantons of Geneva and Vaud.

On 21 June, violent thunderstorms struck the Val-de-Ruz area (canton of Neuchâtel). The ensuing floods led to major damage and also caused the death of one person in Villiers. These events in the cantons of Geneva, Vaud and Neuchâtel alone accounted for three quarters of the damage sustained in Switzerland in 2019. The concentration of the damage on theses cantons is unusual, just as are the below-average damage levels observed in the Alpine region.

 
 

Five fatalities

 

While the cost of flood and landslide damage was relatively low in 2019, there were sadly five fatalities. Two people were killed by rockfall, while one person died in the flash flood that struck Villiers (canton of Neuchâtel) on 21 June. Two more people lost their lives in Chamoson (canton of Valais) on 11 August when a debris flow in the La Losentse river swept their car away.

 

The Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) has been systematically collecting information on storm damage since 1972. The database created with significant support from the Federal Office for the Environment (FOEN) contains data on damage caused by floods, debris flows and landslides and, since 2002, rockfall, rock slides and rock avalanches. Damage caused by avalanches, snow pressure, earthquakes, lightning strikes, hail and gales is not taken into account. Estimates of property, infrastructure, forest and agricultural damage are based primarily on media reports. The data are available to experts upon request and constitute an important basis for risk assessment.

 

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