The word from Guy Carpenter after the flooding in Central Europe;
The estimated market losses from the September 2024 floods stand between EUR 1.6 billion and EUR 2.1 billion. Although the region faced significant rainfall and flooding, the damage in real terms is notably lower than previous events, such as the major floods of 1997 and 2002.
This reduction in losses is largely due to improved flood risk management and heightened public awareness across the region. Investments in flood defenses and timely preventive measures such as pre-emptive predicative reservoir management and reinforced levees, alongside more accurate early warning systems, played a key role in minimizing the financial impact and safeguarding major urban centers.
Hydrometeorological Assessment
This event was characterised by large-scale circulation patterns which caused a prolonged period of heavy rainfall. This led to widespread flooding across Central Europe. Large meanders in the jet stream resulted in a wave of cold air plunging southwards from the Arctic across
Europe. This cold air clashed with warm moist air coming off the Mediterranean and Black Sea. High-pressure systems over Western and Eastern Europe blocked a surface low pressure system from moving away from Central Europe.
HISTORICAL DATA
2002
Forecast maps show many similarities to the floods of 2002 which led to devastating floods for Austria, the Czech Republic and parts of Germany. That event was the result of a Vb-type cyclone named Ilse causing a multi-day flood event that overwhelmed the Elbe and Danube catchments. Here we saw very humid air, advected from the Mediterranean Basin around the eastern Alps. A frontal zone stalling over the affected area
for a significant amount of time and airflow up the Central European mountains aided the cooling of the air that resulted in heavy rainfall. The event resulted in intense rainfall of around 320mm over 2 days in the Erzbirger Mountains.
1997
In 1997, both the Oder and the Vistula rivers swelled to levels that had return periods in the 1000s of years. The event saw peak rainfall of 585mm between 4 and 9 July (recorded at a mountain site). The flooding was associated with an upper cut off low over Southeast Europe. The cyclone track was similar to the current event as the surface low tracked from the Mediterranean to Central Europe near the eastern Alps (Vb track). Vb tracks have potential to lead to extreme rainfall due to their advection of humid air, frontal uplift and flow up the northern slopes of the Alps—all ingredients for high intensity rainfall. When this combines with slowmoving upper-level dynamics, such as blocking, these can cause multi-day events with continual moisture supply and lifting mechanisms, hence the high accumulations seen in these scenarios.
IMPACT
Austria
The province of Lower Austria has been declared a catastrophe zone, with emergency services making nearly 5,000 interventions where flooding had trapped residents in their homes. The residents in approximately 24 villages in the region have been evacuated. Rail services have been suspended in the country’s east, with similar disruption across the metro services in Vienna. The whole of Lower Austria has now been declared a disaster area. In terms of infrastructural damage, the A1 motorway near St. Pölten was flooded and partial closure of the Western Railway line (the most important W-O connection) and disruptions to the Vienna subway and other train services have been reported. There have also been repeated power outages in Vienna and the Lower Austria District of St. Pölten (Harland) and the Alpine train station is under water.
Additionally, Danube tributaries overflowed their banks (Kierlingbach, Triesting, Wienfluss, Göllersbach, Erlauf, Kamps).
Poland
Approximately 1,600 people have been evacuated in Kłodzko in Lower Silesia, which was partly under water as the local river rose to 6.7 meters due to the Poplar retention reservoir failure near the village of Kozielno on the Nysa Kłodzka River. As a consequence, the center of Kłodzko was fully flooded. Further floods have been recorded in the Jelenia Góra region. In terms of infrastructural damage in Nysa, a hospital has been
evacuated and the viaduct in Lądek Zdrój collapsed. In terms of dam breaches, overtopping has been recorded in Pilchowice and there was a dam breach in Stronie Śląskie.
As a new prevention measure, the Racibórz Dolny reservoir was launched. The reservoir receives water rising from the Oder River. Its purpose is to lower the valves of the overflow and drain structure, with the ultimate goal of protecting cities like Kędzierzyn-Koźle, Opole, Wrocław and smaller towns.
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