The measures that Vienna has implemented to prepare for extreme heavy rainfall could serve as valuable lessons for other cities facing flooding challenges.
Storm Boris is the latest flooding event in one of the most significant flood periods in Europe in the past 500 years, yet one city remained largely unaffected, according to BBC. When record rainfall from Storm Boris fell on Vienna on September 15, the impact appeared severe with flooded streets, evacuations of homes, and a stream turning into a raging torrent. Within just five days, the rainfall recorded in Vienna and many other areas in Austria was 2 to 5 times the average for September. However, despite the intense downpours, local residents suffered minimal damage, with estimates of only 10 people sustaining minor injuries and 15 homes needing evacuation. Overall, the city’s advanced flood management system successfully mitigated a large volume of water.
Vienna constructed the New Danube flood control channel in 1970. (Photo: BBC).
In fact, evidence from past major flooding events indicates that some protective strategies employed by Vienna specifically and Austria generally are proving effective, providing crucial lessons for other cities coping with increasingly extreme weather. “Austria has genuinely invested in flood management for several decades, particularly after experiencing two major flooding events in 2002 and 2013,” said Günter Blöschl, a hydrologist and director of the Water Resource Systems Center at the Vienna University of Technology, who has helped shape Austria’s flood risk management strategies.
According to Blöschl, in Vienna, a flood prevention system developed several decades ago plays a key role in protecting the city. The flood prevention system in Vienna is designed to handle flood flows of 14,000 m3/second, equivalent to a 5,000-year flood event. A flood of that magnitude occurred in 1501. During the most recent flooding event, approximately 10,000 m3/second of water flowed through Vienna’s waterways, significantly lower than the system’s capacity. Without this system, widespread flooding would have occurred.
The cornerstone of this flood prevention system is the artificial island known as Danube Island and the New Danube flood control channel. Both were constructed in the 1970s after a severe flood in 1954 overwhelmed existing protective systems. The New Danube is typically dammed, creating a reservoir. The dam is opened before floods arrive, and the channel allows water to flow through for 3 to 4 days, reducing pressure on the Danube River as it flows through Vienna, according to Blöschl.
The system faced a significant test in 2013 when the upper Danube Basin experienced one of the largest floods in two centuries. The flood flow of the Danube in Vienna reached around 11,000 m3/second, but Vienna avoided severe damage thanks to the city’s flood prevention system. No homes in Vienna were threatened compared to 400,000 households across Austria.
However, this does not mean that the system can completely control large floods. During the most recent flooding event, the Wienfluss, a smaller river in Vienna, overflowed, flooding subway tracks and disrupting public transportation.
Austria as a whole has also strengthened its flood prevention efforts. The country invests around $67 million annually in flood protection measures and has seen a decrease in damage. These protective measures include regularly conducting emergency drills with movable walls to block significant water flow, as well as employing advanced and more accurate forecasting systems.
According to assessments by authorities, the 2002 flood caused $3.6 billion in damages across Austria. Although the 2013 flood was also significant, its damage was much less, around $967 million, thanks to flood protection measures. Data also indicates the accuracy of forecasting. After the flooding on September 13, 2024, the Austrian weather agency noted that the actual rainfall matched the predicted levels. “Considering the impacts of last week’s flooding, we find the flood prevention system to be incredibly valuable. The damage we avoided far exceeds the investment in the system. This is a success story,” Blöschl shared.
In Austria, accurate forecasting and flood management drills have saved lives during the most recent flooding event, not only in Vienna but in many other areas across Austria. The emergency response teams practiced erecting movable walls to prevent flooding. Accurate forecasts also help identify where dams are at risk of overflowing and where residents need to evacuate. Research findings indicate that preparation is particularly crucial in the context of climate change, which is leading to increasingly severe storms and more flooding in certain regions of Europe. One reason is that warmer air holds more moisture and energy, fueling powerful storms like Storm Boris. The summer of 2024 was the hottest summer on record in Europe and globally. In fact, record rainfall and widespread flooding are occurring more frequently in Europe. It is estimated that 1 in 8 Europeans lives in flood-prone areas.
