The breakthrough of the flood relief tunnel between Langnau am Albis and Thalwil has been completed. From 2026, the tunnel will reliably protect Zurich from flooding. Find out exactly how in the video.
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- The breakthrough at the flood relief tunnel in Thalwil took place on November 26, 2024.
- The relief tunnel between the Sihl and Lake Zurich is one of several measures commissioned by the canton and city of Zurich to combat the risk of flooding.
- Watch the video to find out how the relief tunnel in combination with the active Sihl control system will protect the city on the Limmat.
When it rains heavily in the Sihl Valley, the tranquil river can turn into a raging torrent and become extremely dangerous for the city of Zurich.
Billions in damage
The last time the Limmat metropolis narrowly escaped a devastating flood was in 2005. According to experts, if the water had burst its banks in the area of Zurich's main railway station, it would have caused damage amounting to 6.7 billion Swiss francs.
Zurich focuses on prevention
Since then, the canton has been improving flood protection step by step. In addition to active Sihl control and other construction measures along the Sihl, the relief tunnel between Langnau am Albis and Thalwil will make a significant contribution to Zurich's flood protection from summer 2026.
Watch the video to find out how the flood protection along the Sihl will work and what is meant by active control of the Sihl.