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Lee Kuan Yew World City Prize

Vienna – Flood prevention via New Danube and Danube Island

29 June 2023

Discover how Vienna's long-term flood planning turned a river threat into a thriving leisure and nature destination.

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Vienna's foresight and long-term planning into the future helps the city avoid devastating floods and safeguards its safe growth.[^1]

Case study 19

| City | Vienna | | Type | Climate change adaptation | | Location | Danube river, city centre | | Sections| 1   In brief
2   Key issues before project
3   Leadership/governance
4   Creativity/innovation
5   Impacts
6   Replicable ideas |

In brief

Aerial view of a city with highways crossing a blue river, green trees, and a tall skyscraper under a blue sky.

New Danube (lighter shade of blue) and Danube Island in Vienna's city centre © Cristi Croitoru/123RF

  • Vienna embarked on creating a flood relief channel (New Danube) in 1969 to mitigate potentially devastating floods, especially those exacerbated by climate change.

  • The new 21.1km-long, 210m-wide channel runs alongside the existing Danube, with its excavated soil forming a recreational island in between – Danube Island.

  • The Danube remains as a main navigation channel, while the New Danube is activated via weirs to absorb excess water volumes during flood events.

  • Otherwise, the New Danube and Danube Island are used for leisure purposes for most of the year.

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Key issues before the project

  • The Danube is key to Vienna’s urban development as a flood would be detrimental to the city.

  • In the 1870s, the city widened and straightened the existing Danube and created a 450m-wide inundation zone and a flood protection dam, catering to a maximum flood water volume of 11,700m3/s.

  • The 1954 flood highlighted the need to further increase the protection levels to handle larger flood volumes up to 14,000m3/s, statistically expected to occur every 3,000 to 5,000 years.

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Leadership and governance

Two people in a small blue and white boat numbered 37 on a lake, with more boats, trees, and buildings in the background.

Leisure activities on the New Danube during non-flood times © Przemyslaw Iciak/123RF

  • The city called for the architectural and landscape design of New Danube and Danube Island via an open competition.

  • A team made up of hydraulic engineers, architects and landscape planners worked closely during the planning and implementation phase.

  • The processes ensure that the project not only serves its primary function of flood protection, but provides free-of-charge leisure options, water and energy production, and nature and biodiversity protection.

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Creativity and innovation

Outdoor vegan festival with white tents and crowds near a waterfront, city tower and tall buildings in background.

People enjoying a festival on Danube Island © nito500/123RF

  • Danube Island is raised at least 1m above projected flood levels, offering a 390ha flood-free surface.

  • New Danube is designed as a large usable waterbody for water sports, with inlets and basins for docking rowing boats and sailboats.

  • Danube Island is designed as a large park with its ends as forested zones and meadows, and integrated old river branches with residues of riparian forest and ancient trees.

  • A facility built to absorb the wastewater from the Eastern bank helped prevent the contamination of New Danube.

  • A controlled introduction of water to the Lobau floodplains nature reserve helped prevent further depletion of water volumes due to reduction of groundwater levels..

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Impacts

Three circular icons showing electricity plug, flooded house, and canoe with paddle, with Danube River statistics below each.

  • The farsighted planning allowed the city to continue growing on the banks of the Danube and offer a high quality of life.

  • The flood protection system helps the city avert major damages during flood events, such as during a record torrential downpour in July 2021.

  • New Danube and Danube Island are popular leisure destinations today, with frequent large-scale cultural and sporting events, such as Danube Island Festival.

  • The project with its careful landscaping has seen an increased in biodiversity.

  • The Freudenau Power Plant completed in 1998 provides 1.037 billion kWh of electricity per year, sufficient to supply over 280,000 households or half of Vienna’s private households.

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Replicable ideas

A large canal lock facility with a control tower, blue steel bridge, crane, and orange machinery under a blue sky.

Hydro Power plant Freudenau © Daniel Dutkowski

  • Taking the long-term view, a city can turn potential threats into opportunities.

  • Vienna’s forward-looking plans allowed the city to continue to grow safely and sustainably, even before climate change entered the mainstream vocabulary.

  • Creative and integrated approaches allowed the city to look beyond a mere infrastructural solution, but developing multiple uses, especially those that would benefit the people directly. O

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[^1]: The information in this case study is correct as of 2019.