Property protection for Sihlcity, Zurich

The basic hazard data available in 2008 showed that the Sihlcity leisure and shopping center was at risk of flooding due to an outburst of the Sihl from a 100-year flood. The depression in the Giesshübelstrasse area was particularly at risk, as all basement levels could be flooded via the underground parking garage entrance located there. The aim of the project was to ensure flood protection for Sihlcity up to a 300-year flood event. Taking into account the flooding processes, measures were developed, analyzed and evaluated in terms of feasibility and costs. Finally, a comprehensive protection concept was implemented, which included numerous measures - from flood protection gates to flood protection doors, the sealing of pipe penetrations to mobile hose dams and insulating beams.

When the City of Zurich's risk map was revised, it became clear that the risk posed by the Sihl had been underestimated in the original survey. The protective measures implemented are currently not sufficient to protect against a 300-year flood. However, the Sihl-Zürichsee relief tunnel will go into operation in 2026, which will greatly reduce the flood risk. A review of the measures was therefore carried out in 2024 with the aim of optimizing the flood protection of Sihlcity both in its current state and in the state after commissioning of the relief tunnel.