Flood alert! The Rhine floods in Bonn
Bonn last experienced a flood on the Rhine in January 2025. The water level rose to just under 7.50 m, exceeding the lowest flood mark by half a metre. No big deal for long-time residents of the Rhine. First on the right bank of the Rhine in Beuel and then at a few other locations, the riverside promenades were closed off. The car ferries could no longer be reached, and an important tram service was suspended as a precaution. Nothing happened. It was more of an opportunity for a Sunday outing on the banks of the Rhine.
The flood disaster of 1784 was quite a different matter. Apart from two extreme cases in the 14th century, about which there are no precise records, it was by far the worst flood event on the Rhine in historical times. Although the Bonn Rhine gauge has only existed since 1820, the flood of 1784 can be reconstructed. It reached over 14 metres, which is 4 metres higher than any other flood in the last 650 years. On the right bank of the Rhine, the floodwaters extended as far as the area of today’s Beuel railway station. With the exception of Wolfsburg, a medieval moated castle, all the houses here were destroyed. Even in Bonn, which is normally flood-proof, the districts facing the Rhine, including the Jewish quarter, were severely affected. The water is said to have even reached the rear of the city centre via the former city moat and to have stood in the cloister of the cathedral. The fact that there were hardly any deaths or injuries was due to the particular nature of this flood. Whilst ‘normal’ floods are the result of rain or snowmelt in the major tributaries and move relatively quickly along the Rhine as a flood wave, this time ice played a major role. Arctic temperatures prevailed for more than two months, repeatedly interrupted by heavy snowfall and brief periods of thaw. The ice floes piled up to form barriers; the water could not drain away and, weeks before the actual disaster, it slowly rose higher and higher. This at least gave people time to save themselves and their animals. When the ice dams finally broke at the end of February, it was the ice floes that caused the greatest devastation.
The Bonn area has been familiar with flooding ever since people have lived here. The city and the settlements from which it grew are situated in a landscape shaped by the Rhine. Between the Siebengebirge and the Ennert in the east and the Kottenforst and the Venusberg in the west, it has carved out a valley funnel that is still criss-crossed by former river branches. They are still there, but are barely recognisable in today’s cityscape. People have been slow to settle in this landscape. The earliest traces of human habitation come from the slopes of the Venusberg and the Ennert. The lower terrace, lying only slightly above river level, was settled relatively late; specifically at carefully selected points safe from flooding. Here, a few metres could make all the difference. The area of what is now Bonn’s city centre has always been the safest. Its highest point on Acherstraße lies about 20 metres above the zero line of the modern Bonn water gauge.
Old settlement centres such as Muffendorf, Friesdorf and Rüngsdorf in the south of Bonn are similarly safe. Parts of the urban area on the right bank of the Rhine, in the vicinity of the former town of Beuel, remain significantly more at risk to this day.
Anyone wishing to learn more about what the Rhine’s floods can still mean for Bonn today is recommended to take a walk along the Beuel bank of the Rhine. Here, at various points, there are markers documenting past floods, and everywhere the walls and floodgates that form the first line of defence are visible.
Today, this provides protection up to a water level of 9.50 m, with a second line behind it offering protection up to 11.50 m. In Rheinaustraße, the ground-floor flats in many buildings are actually on the first floor. The actual ground floor houses only garages and storage rooms – a reminder of a time just a few years ago when an 8.50-metre flood reached this far. The flood defences are particularly robust in the north of Beuel. The Rhine embankment towards the mouth of the Sieg is not only a lovely walking path, it also provides protection against floodwaters up to 11.50 metres. There is nothing comparable along Bonn’s Rhine promenade. Whilst south of the Alter Zoll the buildings have always stood high up on the steep slope, the urban districts further north were secured by raising the riverbank; once in the second half of the 19th century during the construction of the Rhine promenade, and most recently immediately after the Second World War. At that time, the rubble from the bombed-out old town was used to raise the Rhine bank by almost two metres. The original height can still be seen at the foot of the bridge pier, where a section of the old promenade has been preserved.
The years 1993 and 1995 demonstrated that dramatic floods still occur even today. In both instances, the 10-metre mark was exceeded. The fate of the so-called ‘Schürmann Building’ made headlines. Originally planned as an extension of the Federal Parliament building and now the headquarters of Deutsche Welle, its shell was pushed upwards by the groundwater from the 1993 flood and subsequently stood at an angle. Those responsible did not, as had actually been planned, flood the underground car park at the time, because the ventilation system intended for installation was being stored there temporarily. The damage was enormous. Nevertheless, the federal government decided against demolition and in favour of completing the building. It was the events of these two years that led to a significant strengthening of flood defences, particularly on the right bank of the Rhine. This included a major overhaul of the sewerage system to prevent water from entering via this route.
Even though the focus these days tends to be on the average water levels that have been falling for several decades – thanks to climate change – because they jeopardise the Rhine’s functionality as a waterway, the issue of flooding will continue to be a concern for Bonn in the future.
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