Authorities partly inadequately assessed the risk of severe weather in Misox
Published: Monday, Nov 25th 2024, 18:50
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An analysis of last June's storms in the southern Graubünden valley of Misox revealed that the authorities had in some cases inadequately assessed the risk of severe weather. In many places, more debris was washed up than expected. Nevertheless, the government refuses to accept liability.
Two people died in the storms on June 21. One person is still missing. Strong thunderstorms led to numerous debris flows that caused considerable devastation throughout the valley. In Sorte GR, a debris flow reached a settlement of almost ten buildings, destroying three of them and damaging the others. Until reliable protective structures are in place, the 20 or so residents will not be able to return.
An external geoscientific office has now analyzed 18 of a total of 50 streams that caused damage. It was found that for a third of these 18 streams, the authorities' hazard maps did not correspond sufficiently with the event, as the experts explained on Monday in Lostallo GR.
The maps are therefore now being revised quickly. The canton of Graubünden intends to present the first results as early as the first quarter of 2025.
Resettlement not ruled out
This could have serious consequences for those affected. If new hazard zones are designated, buildings could also be affected. However, such buildings are not permitted in these danger zones, as the head of the cantonal office for forests and natural hazards, Urban Maissen, told Keystone-SDA.
How to proceed would then have to be considered on a case-by-case basis. In principle, there are organizational, structural and spatial planning measures. The latter would also involve the possible relocation of people. Ultimately, it is important to choose the best option in terms of safety and the concerns of the population.
The authorities, under the direction of the municipality, want to examine the measures for Sorte GR by the summer and decide on the future of the village.
Liability excluded
The hazard map for the hamlet in question dates back to 2013. These maps are regularly reassessed every 10 to 15 years. At that time, the work was based on current knowledge, Maissen continued. The responsible government councillor Carmelia Maissen (center) also agreed and ruled out liability for the devastation and deaths in the valley.
The decisive factor for the deviations in the hazard maps was the amount of material that was washed down. In the case of a debris flow further south of Sorte GR, a maximum of 15,000 cubic meters of debris was expected. In the end, up to 100,000 cubic meters came down. According to the analysis, events of this magnitude occur every 100 to 300 years.
Climate change influences hazard mapping
According to Urban Maissen, the fact that in many places there is more material than assumed in the hazard maps is something that has been experienced throughout Switzerland this year. He referred to the events in Brienz BE and in Ticino.
Around a week after the storms in Misox, the upper Maggia Valley in the canton of Ticino was hit by heavy thunderstorms. At least seven people lost their lives in mudslides and landslides in the Maggia and Bavona valleys. One person is still missing. The Visletto bridge near Cevio TI was washed away.
In August, a storm raged in Brienz in the canton of Bern. Up to 100 millimetres of rain fell in the catchment area of a village stream, which covers around four square kilometers.
These more frequent and more intense heavy precipitation events are due to climate change, as explained by Head of Office Maissen. This fact is now to be incorporated into the new hazard maps. They are in close contact with the federal government, which is currently developing findings on possible climate scenarios.
©Keystone/SDA
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