Floods in Lucerne: City is researching the cause

The Lucerne Würzenbach district has a notorious problem. However, the Gerlisbergbach was not to blame for the recent event. And: Compared to the July flood, the damage is limited.

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If the fire brigade had to build a new guard in the city of Lucerne, the area between the Verkehrshaus and the sports center in Würzenbach would be ideal. No other area is more at risk of flooding than this. Latest example: On Monday afternoon, parts of Haldenstrasse and the Brüelkreisel were under water. The result: traffic disruptions and course cancellations in urban transport companies. The fire brigade was still busy pumping water out of the sewage system on Haldenstrasse yesterday. Therefore, traffic disruptions were still to be expected.

The reason for the renewed flooding is still unclear, says Miriam Asanger. The head of the urban drainage and natural hazards department of the city of Lucerne can already say: “It is not the same cause as the flood one month ago.” In the evening of July 2, the Gerlisbergbach in particular caused damage. This shot over the concrete wall at the canalized stream on Schlösslistrasse beyond the Schadrütistrasse.

5 reports – 50,000 francs damage

How long it takes to determine the reasons for the current flood is not yet clear, according to Asanger. What is certain is that the underpass at the Brüelkreisel is like a depression in which the water collects. Finding the exact cause is “like looking for a needle in a haystack,” Asanger continued. The canton is currently not involved, as no water has overflowed its banks.

After all, the Monday flooding only resulted in minor damage in the Würzenbach district. So far, according to the deputy director of building insurance Lucerne, Heinz Achermann, five damage reports have been received. “We estimate the total damage to be around CHF 50,000,” says Achermann.

Fortunately, this is just a tenth of the damage caused by the flood in early July in this district. At that time, the building insurance company processed between 80 and 100 damage reports. Whether small or large damage: According to Achermann, it is important for building insurance that such events no longer happen in the same place: “We invest a lot in prevention and are also in regular contact with the canton.”

The city, canton and fire departments have been dealing with the flood events in this district for years. A brief overview:

• 21./22. August 2005: In the night of that Monday, the Würzenbach overflows. The Verkehrshaus is particularly affected: two thirds of the historic railways are up to 30 centimeters in the water. Including the Spanish bread railway. The Verkehrshaus complains of damage in the millions. The “flood of the century” is also causing enormous damage in the agglomeration and in the rest of Central Switzerland.
• 29. August 2014: Heavy rain in the early evening clogs a debris catcher at the Brüelkreisel. The water can no longer drain and accumulates up to 25 centimeters on Haldenstrasse between the VBL bus stop Verkehrshaus and the roundabout Verkehrshaus.
• 7. June 2015: A big storm ensures that the Würzenbach overflows. There is a relief tunnel with a retention basin, but the system stops working after a certain amount of water. In addition, an extraordinary number of branches and roots are washed up on that Sunday. The floods cause damage in the Verkehrshaus and the Romerohaus, among others. Building insurance speaks of presumed costs of three to four million francs.

Researchers recreated the model

The authorities did not remain idle after the past events. After the 2015 flood, ETH Zurich was commissioned to carry out model tests on the Würzenbach. For this purpose, the researchers have reproduced a model of the brook and the gallery that is fifteen times smaller.

The canton then invested almost two million francs in flood protection, with the federal government contributing almost one million. The city also took immediate measures. It will be shown if the cause is clear whether further measures are needed after the current flood – and if so, which ones.