Flood water retention for the city of Winterthur

The city of Winterthur is at risk from flood water from the Eulach river. Bridges and culverts in the city centre can become problematic in the event of an extreme event, and lead to flooding in the centre. A spacious retention area is created to hold back a large proportion of any flood water before it reaches the “city gates”.


Building Department, canton of Zurich

Protection for Winterthur

The new retention area, which is expected to come into play once every 30 years for flood relief, is created in the Hegmatten area near Oberwinterthur on public land that comprises a gliding facility, football fields and farmland. As the Eulach reaches a critical level, some of the water will be diverted via underground channels into the dammed area.


A hidden large-scale project

It might sound simple, but requires significant construction measures, and the new diversion structure with its supply channel to the retention area will be built right in the middle of the residential area. The work involves a selection of impressive structures. The underground diversion structure alone is as wide as a 4-lane motorway and 100 metres long, while the supply channel is 5 metres wide and almost 400 metres long. Added to this is the up to 3.5-metre-high dam along the retention area, a driftwood retention structure, and rewilding work. A large-scale project that, once the work is complete, will disappear into the ground and blend in with the newly designed landscape.


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