Floods in Vienna: Why Vienna is under water

I grew up here, but I rarely saw the city like this. The last comparable floods occurred in 2002 and 2013.

The Danube was regulated 150 years ago to prevent flood damage. And in the 1970s, Vienna even built its own island specifically for flood protection. So why did motorways and subways still have to be closed?

The most famous river that flows through Vienna is the Danube. The problem with this flood was over this whole river here – the Vienna River. It rises here in the west, in the Vienna Woods, and flows into the Danube Canal, a tributary of the Danube.

Calling the Vienna River a “river” is usually an exaggeration. When it is dry, 200 l of water flow here every second – 0.2 cubic meters. About a full bathtub. In the city it looks more like a trick, for example. This is what the Vienna River looked like this weekend.

The Vienna River is actually ready for flooding: it was made straight around 1900 and placed in a deep bed with tiles.

By the way, the construction work was immediately used to build a light rail system. Today it’s the subway, and it can’t run because water is pouring on the tracks – but that’s only a little.

The Vienna River not only has its bed, but also a flood protection system, here on the city limits, in Hadersdorf, with seven backwater basins. These can temporarily store over a million cubic meters of water. But once they are full – and that was the case this weekend – the water has to go into the Danube Canal.

And there is the problem: The water of the Danube usually flows through the main branch and through the Danube Canal through Vienna. When the water level is high, the inflow from the Danube into the Danube Canal is stopped here near Nussdorf so that the inner areas are not flooded.

Further downstream, near Freudenau, where the Danube Canal and the Danube meet again, the water from the Danube pushes into the canal and causes backwater. This back-up extends into the city centre.

This is exactly where all the water from the Vienna River enters the Danube Canal. But because it is already so full, the water can only drain slowly.