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WEATHER

How the New Danube protects Vienna from catastrophic floods

Built in the 1970s, the value of the New Danube has been driven home this week, where it has helped Vienna avert a flooding catastrophe.

How the New Danube protects Vienna from catastrophic floods
The Donau Canal (right) seen aside from the Donau. Photo By Bwag - Own work, CC BY-SA 3.0 at, https://commons.wikimedia.org/w/index.php?curid=20756455

While rivers burst their banks across the country and several areas were hard hit, Vienna managed to escape the worst. 

This week, the Danube (Donau) river is expected to flow over its banks, but instead of flooding Vienna’s historic streets, it will flow into the New Danube – the channel built in the 1970s to protect the city of Vienna. 

“The “New Danube” is flooded so that the Danube does not overflow in Vienna.  The New Danube and the Danube Island were built in the 1970s for this purpose.”

What is the New Danube?

The New Danube is a side channel built into the Danube River. The design of the channel was made in 1969, with construction taking place from 1972 to 1988. 

The Donauinsel (Danube Island) is 21 kilometres long and now sits in the middle of the two waterways and was constructed from rocks and dirt dredged out of the river. 

The International Knowledge Centre for Engineering Sciences and Technology reports that few areas of the city were protected from large floods. 

“Vienna was over many centuries subject to severe flooding. Only the very oldest parts of town, where the Roman fort was once established were flood free.”

Catastrophic flooding events took place in 1897 and 1899, which led to smaller scale changes to try and reduce damage. 

The idea for the channel gained momentum after 1954, when another catastrophic flood hit Vienna and authorities realised that a more drastic change was needed to properly protect the city from flooding. 

How does it work? 

At the entrance to the New Danube channel, there is an openable weir which stops water from the Danube from entering. 

In normal times, the weir seals off the channel which makes it perfect for swimming and other water activities, while facilities were built on the land to allow for volleyball, skating, jogging and other activities. 

Up to 300,000 people can use the area each day. 

The entrance weir to the Donau Canal. Photo By User:My Friend – Own work, CC BY-SA 3.0. 

The weir is so popular some people use it to commute to work, giving it the nickname “the autobahn for swimmers”. 

When the water level rises in the main river, the gates are released to reduce pressure on the main part of the river and allow water into the channel. 

As has happened in 2021 with the high water levels, this will usually mean swimming, boating and other water activities are banned in the channel. 

There are two other weirs further down in the channel which help to regulate water level during non-flood periods. 

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WEATHER

‘Achtung… Gefahr’: What do Austria’s weather warnings actually mean?

Austria's national weather agency issues warnings for potentially dangerous weather on a scale from yellow to red. But what does the weather alert system mean, and what should you do if there's a warning?

'Achtung... Gefahr': What do Austria's weather warnings actually mean?

As Austria gets more affected by global warming, the frequency of extreme weather increases. 

Austria has an advanced system of warnings led by the country’s Meteorological Service GeoSphere Austria. “Our regular verification shows a high level of accuracy in the warnings. This is very important for the acceptance and behaviour of the population,” said Dr Andreas Schaffhauser, Scientific Director General of GeoSphere Austria. 

He added: “The better and more comprehensible warnings of major weather events are, the more seriously they are taken and the greater the chance that people will respond to them.”

Austria follows a traditional weather warning system consisting of three colours: yellow, orange, and red.

READ ALSO: How prepared is Austria for extreme weather events?

A yellow warning means caution (Vorsicht!). It means that caution in the current weather scenario is urged, but only isolated weather-connected endangerment and/or damages are anticipated.

An orange warning means attention (Achtung!!), as the current weather scenario can lead to endangerment, disturbances in everyday life and damages. People should pay close heed to the ongoing weather forecasts.

Finally, a red warning means danger (Gefahr!!!). In this case, the current weather scenario is expected to lead to extensive endangerment, disturbances of everyday life and/or considerable damage. People should pay close heed to the ongoing weather forecasts and comply with the instructions of the Civil Defence. 

Each warning is usually issued for one or more weather conditions such as wind, rain, snow, black ice, thunderstorm, heat stress and cold stress.

READ ALSO: What is Austria’s official emergency-warning phone app, and do I need it?

Avalanche risk

The European Union has an online tool to check the dangers of avalanches, the European Avalanche Warning Services. You can zoom in and click on the province where you are travelling to get more information, or just check using the links below:

There are no high mountains with a risk of avalanches in large parts of Upper Austria, Lower Austria, and the entire provinces of Burgenland and Vienna.

There are five danger levels in Austria: 1 – low (green), 2 – moderate (yellow), 3 – considerable (orange), 4 – high (red) and 5 – very high (red and black). These colours are also used to mark avalanche risk in loco, so if you see an avalanche sign in orange, for example, it indicates a considerable risk in that area. 

READ ALSO: Avalanches in Austria: What you should know to stay safe in the mountains

Danger level 5 is rarely forecasted, while danger level 3 is forecasted for around 30 percent of the winter season. Approximately 50 percent of avalanche fatalities happen while the level is “considerable”.

Warning systems

In case of more severe or sudden alerts, Austria also has emergency systems in place. For example, the country’s civil defence alarm has nationwide warning siren systems.

Different sounds mean different things: 

  • TESTING (15 seconds continuous tone): A quick continuous tone to test whether sirens work correctly.

What to do: don’t panic; this is only a test. You can check ORF on radio, TV or online to confirm this.

  • WARNING (3 minutes continuous tone): A constant continuous tone with a length of 3 minutes means “warning”. This signal is triggered when the population is warned of approaching danger.

What to do: Switch on radio or TV on public broadcaster ORF, or check www.orf.at and follow the rules of conduct.

  • ALARM (1 minute rising and falling wailing tone): An ascending and descending wailing tone of at least 1 minute duration means “alarm” and alerts that the danger is imminent.

What to do: Switch on radio or TV on public broadcaster ORF, or check www.orf.at and follow the rules of conduct. Look for protective areas or rooms.

  • ALL CLEAR (1-minute continuous tone): A constant continuous tone of 1 minute (only after the alarm signal) means “all clear”, i.e. end of danger.

What to do: Continue to pay attention to the announcements on the radio, TV or ORF online, as there may be certain temporary restrictions.

READ MORE: Austria’s civil defence alarm: What you should know about the warning siren system

The Ministry of the Interior’s official smartphone app, KATWARN, is a system that displays information and warnings from various authorities on a location-based or topic related to smartphones.

The app complements the existing warning options such as sirens, loudspeakers and media broadcasts. The advantage is that it can immediately warn people of any significant events, informing them of the danger and, just as important, giving immediate information on how to behave.

If you live in Vienna or go there often, the official Stadt Wien app is very useful. It brings essential news and pushes notifications on traffic disruptions near you, weather alerts or civil emergencies.

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