Flood risk largely averted after three days of continuous rain
Published: Wednesday, Nov 15th 2023, 17:20
Updated At: Wednesday, Nov 15th 2023, 17:24
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After three days of continuous rain, the flood risk on the northern slopes of the Alps largely calmed down on Wednesday. Previously, the Arve near Geneva had reached the highest discharge ever measured.
According to MeteoSwiss, widespread precipitation of 80 to 100 millimetres fell on the northern slopes of the Alps in the past 72 hours, 100 to 150 millimetres in the Glarus Alps and the Alpstein and as much as 110 to 180 millimetres in the Lower Valais and the Vaud Alps. Meteonews reported the Säntis as the frontrunner on its blog with over 200 millimetres.
Highest risk level
These large amounts of rain led to a rise in water levels on the northern side of the Alps. Added to this was the high snow line and the associated meltwater.
The Saane, Gürbe and Kander rivers in the cantons of Fribourg and Bern, as well as the Arve near Geneva, subsequently reached the highest hazard level 5, according to the natural hazard bulletin published by the Federal Office for the Environment (FOEN). The Mentue, the Broye, the Veveyse and the Simme were at level 4 in the meantime.
The highest water levels were reached during the night, after which they fell "markedly". Only for the Arve near Geneva, the Aare before it flows into Lake Biel and then as far as the mouth of the Emme, the Rhine from the mouth of the Aare as far as Basel and Lakes Biel and Thun did the danger remain at level 3 "considerable" on Wednesday evening.
Record discharge volumes of the Arve
In the morning, the Arve had the highest recorded discharge in Geneva at 1010 cubic meters per second. Five bridges over the river had to be closed in the meantime. All bridges, with the exception of the Bâtie Bridge, should be reopened shortly, said a police spokesperson late on Wednesday afternoon.
However, the river did not overflow its banks. According to the FOEN's forecasts, its water level should continue to recede and no longer pose a danger by Thursday night. Around 100 firefighters were deployed in Geneva.
The discharge of the Saane also decreased further. According to the FOEN, the warnings for the Aare between Lakes Thun and Biel and downstream to the mouth of the Emme are likely to remain in place.
Due to the high inflows, water levels were still expected to rise on the large lakes on Wednesday. Lake Lucerne and Lake Geneva were therefore at moderate flood risk level 2. The city of Biel called on residents living near bodies of water to evacuate their cellars and stay away from the banks as a precaution.
Floods and landslides
The large amounts of rain kept the emergency services on their toes: during the night of Wednesday, the fire departments in the canton of Valais were called out to 68 incidents due to flooding and around 30 due to fallen trees. Around ten roads in the side valleys were closed due to landslides, including in the Chablais area of Valais and in the Leuk region.
In the cantons of Fribourg and Vaud, rail traffic between Ecublens-Rue FR and Moudon VD was also affected, as reported by SBB. Rail traffic between Biberbrugg SZ and Einsiedeln SZ also had to be closed due to a landslide. Operations were able to resume late Wednesday afternoon.
In the canton of Bern, streams burst their banks in various places. This also resulted in isolated road closures, for example between Kallnach and Fräschels. And in Basel, shipping had to be closed from Rheinfelden AG to Kembs in France. According to the FOEN, the danger level of the High Rhine is not expected to be downgraded until Thursday.
On Thursday, the weather services are expecting a brief respite with an intermediate high. But the next weather-related "considerable danger" is already on the horizon for the evening: MeteoSwiss is warning of strong winds on the entire northern slope of the Alps until Friday morning.
©Keystone/SDA
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