Vienna – Flood prevention via New Danube and Danube Island

29 JUN 2023

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

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.

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.

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.

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..

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.

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