Vienna’s Once in a Blue Moon Flood

The recent flooding in Vienna, after 22 years, marks a significant event in the city’s history, especially given its reputation for strong flood management systems. Vienna is located along the Danube River, one of Europe’s longest rivers, and has faced periodic flooding throughout its history. However, the city implemented extensive flood protection measures in the 1980s and 1990s, including the construction of the Danube Island and the New Danube Channel, which have significantly reduced the risk of severe flooding.

The last major flood in Vienna occurred in August 2002, during what is known as the “European Floods” or the Central European Flood. This event affected many parts of Central Europe, including Austria, Germany, and the Czech Republic. The flooding was caused by extreme rainfall, and the Danube River, which flows through Vienna, rose to dangerously high levels.

Despite the severity of the 2002 floods, Vienna’s flood protection system, particularly the Danube Island and the New Danube Channel and Wasserpark, which were manually created, worked effectively. These defenses were specifically designed to prevent catastrophic flooding in the city. While Vienna experienced some localized flooding and disruption, the city was largely spared from the devastating impacts seen in other parts of Austria and neighboring countries.

Since then, the city has continued to invest in flood prevention and water management, which is why flooding in Vienna is a relatively rare occurrence.

The more recent severe weather event was the 2013 European floods that affected large parts of Central Europe, particularly in late May and June. It resulted from prolonged heavy rainfall, which caused rivers like the Danube, Elbe, Vltava, and Saale to overflow. The flooding impacted countries including Germany, Austria, the Czech Republic, Hungary, Slovakia, and Poland, leading to widespread damage, evacuations, and casualties.

While Vienna’s flood defenses largely protected the city during the 2013 floods, the Danube reached its highest levels since 2002. Some smaller towns in Austria along the river were more severely affected, with roads and railways disrupted. Austria deployed thousands of soldiers to assist with evacuation and flood management efforts.

If Vienna is experiencing this once in blue moon flood, it could be attributed to several factors:

1. Climate Change: Increasingly unpredictable weather patterns, heavier rainfall, and more frequent storms can overwhelm even well-planned systems.
2. Extreme Weather Events: Austria, like many other European countries, has seen a rise in extreme weather events, including heavy rains, which may have contributed to this flooding.
3. Aging Infrastructure: While Vienna’s flood defenses are robust, any infrastructure is subject to wear and tear. If the city’s systems haven’t been upgraded or maintained to handle modern challenges, this could be a factor.

What really happened? It is very seldom that Vienna experiences days of non-stop rain. It started to pour on Thursday, September 12. While it’s not a lot, the continuous days of even small amounts continued on until Monday. Saturday, September 14 was when strong winds accompanied the heavier rain.

The Vienna River, typically a small stream, surged into a powerful torrent, overflowing its banks in Penzing. The Danube Canal and the Liesing River were heavily impacted as well. The flood also caused significant disruptions to public transportation. The lines U3, U6, and U4 were partially closed and buses were deployed to help people commute with ease.

Wiener Linien Flood Response Efforts

Wiener Linien, the city’s public transport operato,  had 700 employees on flood duty last weekend. In preparation, 400 sandbags were set up, and 12.8 tons of dam beams were erected. Despite these efforts, 960,000 liters of water still had to be pumped out, and five kilometers of subway track required cleaning.

Minimal Damage to Public Transport Infrastructure

Thanks to the city’s flood alarm plan, damage to the public transport system was kept to a minimum. This plan dictated the thresholds at which protective actions needed to be taken and when operations had to be suspended. As a result, several subway lines were shut down for a few days, but the impact was controlled.

Nearly One Million Liters of Water Pumped Out

In addition to setting up barriers with sandbags and dam beams, overhead lines and conductor rails were dismantled or de-energized, then reinstalled once the barriers were removed. Seventeen critical locations were monitored around the clock due to water intrusion. In total, nearly one million liters of water were pumped out from twelve different sites.

Subway Lines Inspected for Damage

Before resuming services, every section of the closed subway lines, over 40 kilometers in total, was walked and thoroughly inspected for damage.

Surface Transport and Additional Repairs

On the surface, Wiener Linien crews also had significant work to do. Fifty kilometers of streetcar tracks were cleaned with sweepers, and the incident response team was deployed 50 times. Fallen trees were cleared from roads, including a major incident affecting lines 40 and 41, which was resolved within 36 hours.

There was positive news from the construction site on Universitätsstraße as well, with lines 43 and 44 set to resume their routes to Schottentor starting Saturday.

Water Levels Reached 10 Meters at Pilgramgasse

Cleanup efforts continued at the Pilgramgasse U2 construction site on Thursday, where floodwaters had risen to ten meters the previous Sunday evening. Once cleanup is complete, inspections of the tunnel and station structures for the U2 extension will take place, allowing the next steps and schedule for construction to be determined.