Vienna has been shaping its stretch of the Danube for 500 years. But only in the 19th century was it possible to alter Vienna’s riverscape and revamp public health

In the 1800s, Vienna was just beginning its emergence as a world city, as the population exploded from 230,000 in 1800 to over 2 million by 1910. Vienna was overcrowded, dirty and parched. There just wasn’t enough water, and what water there was, was not fit to drink.

It’s hard to believe today, when Vienna has some of the best drinking water in the world, but back then, access to clean water was a luxury. Most Viennese drank from wells that were chronically contaminated with sewage. How much? In 1830, some 420 tons left the city each day. By 1910, it was 2,600 tons. Everything went into the canals and was eventually “naturally flushed” out to the Danube. When water levels were low, waste would collect in the canals. During a flood, it washed right back up into the streets and into people’s houses.

Under these conditions, it is hardly surprising that infectious diseases like tuberculosis, diphtheria, measles, scarlet fever and typhus were responsible for a third of deaths in Vienna – diseases that most Europeans today have only met in a Jane Austen novel. TB was so common that it was dubbed “morbus Viennensis” – a dubious honor. If that didn’t kill you, cholera epidemics claimed an estimated 18,000 Wiener in the 40 years from 1831-1873. Vienna had a real problem with poop.

The great Danube regulation

Major regulation of the Danube for flood control had been contemplated for centuries, but in the 19th century several things came together that finally made it possible: the invention of high-powered machines, the financial and political means to protect the growing city.

Although similar attempts to reroute rivers were happening elsewhere, the Danube regulation was unique.

“Vienna’s stretch of the Danube has many characteristics of a mountain river, like a comparatively high flow velocity, high fluctuations in runoff and formerly heavy sediment transport. As a result, the Danube was an extremely dynamic river that was difficult to control,” says Severin Hohensinner, a senior scientist at the Institute of Hydrobiology & Aquatic Ecosystem Management at the BOKU in Vienna.

The Danube’s regulation also had the benefit of following several water-taming projects, principally the Suez Canal, completed in 1869, whose planning team included Austrian engineer Alois Negrelli, who, with French overseers Castor, Couvreux et Hersent (and many others) supported the Danube’s reconstruction.

“Regulation is never complete. You never know how big the next flood will be.”

Martin Schmid, associate professor and environmental historian at the Institute of Social Ecology at BOKU Vienna

The Wiener Donauregulierung (1870-1875) was one of the largest construction projects of the Habsburg monarchy, merging many of the smaller branches of the Danube into one straight river, and redirecting water away from the inner city. Excavateurs were brought in from Paris and Draques used in the Suez Canal were purchased second-hand. Almost 1,000 workers would take part creating, most notably, the Inundationsgebiet (a 450-meter-wide designated flood area) and a brand new 280-meter-wide Danube branch to improve shipping.

By drying out parts of the city, Vienna now also had space to grow.

The “new” vienna

“Large parts of the riverine landscape became available for settlements, industrial facilities and other infrastructure,” says associate professor Martin Schmid, an environmental historian at the Institute of Social Ecology at the BOKU in Vienna. Some 20 percent of Vienna’s current territory lies in the former active fluvial zone of the Danube.

With the Donauregulierung, Vienna could now withstand a flood of up to 11,700 cubic meters of water per second (m3 /s), enough water to fill almost five Olympic swimming pools every second while keeping Vienna dry – and the sewage in the canals.

It also enabled the direly needed expansion of the sewer system. “One of the effects was that the groundwater level in Brigittenau and the Leopoldstadt was lowered by about 1.5 meters,” says Hohensinner. “As a result, there was more subsurface space available for a proper sewer system.”

Although public health concerns were not a driving force behind the regulation, it was a happy side effect, reducing the perennial overflow of sewage, and thus the spread of infectious diseases.

At the same time, in 1873, the first Wiener Hochquellenleitung (Vienna Mountain Spring Pipeline) was constructed to bring spring water from Kaiserbrunnen and Stixenstein for the Viennese to drink and to speed up the flushing of the canals. By 1879, more than 70% of households were connected to the pipeline. Water consumption increased enormously. It also catalyzed the construction of concrete sewer lines, which decreased sewage contamination of the groundwater. By 1910, a second Hochquellenleitung was built, bringing an additional 217 million liters of mountain water to Vienna from Styria every day. Access to clean water was no longer a luxury.

Flood protection 2.0

The first Donauregulierung undoubtedly improved Vienna’s response to seasonal flooding. But there were concerns about the capacity from the start, validated by significant flooding in the years directly following.

As the decades wore on, people moved closer to the Danube and accepted flooding as a part of life. In these areas, it was common to have a second kitchen on the first floor for cooking while the ground floor was under water. Only after the disastrous flood of 1954 did people start to resettle outside the flood risk areas, and a second, even more ambitious Danube regulation was seriously considered by the city.

Finally, in the 1970s, Vienna decided to make the move to improve flood control so that it could withstand being hit by the worst flood in its recorded history: 14,000 m3 /s. Construction took place from 1972-1988, including the creation of the New Danube (21.1 km long) and the “flood-free” Danube Island made from the excavated material of the New Danube.

For most of the year, the New Danube maintains a consistent water level, like a lake. In a flood, though, the water is diverted to the New Danube using a system of small dams called weirs. This design spreads out the potential damage of a 14,000 m3 /s flood into just 5,200 m3 /s in the New Danube and 8,800 m3 /s in the Danube, keeping Vienna high and dry.

Climatologists generally agree that extreme weather events, including flooding, will occur more often as a result of climate change. Exactly how Vienna’s current flood regulation will stand up against future, potentially larger, floods remains unknown. What is clear is that keeping the Danube in check while enjoying city life on the water will require vigilance.

“Regulation is never complete,” says professor Schmid. “You never know how big the next flood will be. And you never fully understand what the long-term consequences, the legacies of your own interventions might bring to future generations.” Whatever regulation might be needed in the future, it won’t be a quick fix.

“The Danube we know today is the result of industrialization, of an era with abundant energy,” says Schmid. “How can we manage our coexistence with the Danube in a more sustainable society, a society that has much less energy available?”