The beautiful, idyllic river, along whose banks Bonn stretches, unfortunately also has its pitfalls. The floods in 1993 and 1995 both exceeded 10 meters of the Bonn water level. These were dramatic times for the residents affected by the floods of the century.
We have compiled information on flood prevention for you and provide a brief overview of areas at particular risk. You will also find tips on how to take structural precautions and how to behave in the event of an emergency, as well as an overview of flood protection measures already implemented along the Rhine in Bonn.
Areas at risk
Over the millennia, the Rhine has strongly shaped its surroundings. This also applies to Bonn's urban area with its different terrain heights. Old branches of the Rhine, such as in Limperich, are still clearly visible in the cityscape today.
In brief: The south of Bonn, such as Mehlem and Godesberg, is slightly higher with steeper slopes (Middle Rhine Valley). Towards the north, the terrain flattens out considerably (Lower Rhine Bay). Therefore, Beuel, Geislar and Schwarzrheindorf on the right bank of the Rhine are the lowest lying areas in Bonn and are affected by flooding even at lower flood levels. On the left bank of the Rhine, Graurheindorf and the direct Rhine bank areas up to the southernmost district of Mehlem are affected first.
Bad Godesberg district:
In the district of Mehlem, the situation becomes critical at a water level of around 8.90 meters Bonn gauge. The water then flows into Rüdigerstraße at Am Glückshaus.
Bonn district:
On the Bonn side, the Rathenauufer between Erste and Zweite Fährgasse is the first to be affected. The situation there becomes critical for the riverside promenade and roadway from a Bonn water level of seven meters.
The riverside promenade at Alter Zoll is flooded from a water level of 7.50 meters Bonn level, the Uferstraße from 8 meters Bonn level.
The Graurheindorf district is also particularly affected by flooding. From a level of around 8.70 meters Bonn level, the water floods Estermannstraße from Rheindorfer Bach.
Beuel district:
The Beuel riverside promenade is flooded from a water level of seven meters Bonn gauge.
When the Rhine floods, the groundwater also rises. Therefore, in addition to the floodwater flowing in above ground, groundwater can also be expected to escape to the surface, especially in lower lying areas.
Backwater can also occur in parts of the sewer system. If your sewer house connection is not secured against backwater, this can lead to the flooding of low-lying rooms.
Flood pumping stations in Beuel and Mehlem ensure the normal operation of the sewer system, in some areas also in the event of flooding up to a Bonn water level of 9.50 meters. In the event of malfunctions, the sewer may (in exceptional cases) suddenly back up to the local Rhine water level and surface water can no longer be drained away.
Flood maps
The flood maps in the Bonn city map give you an overview of the flood extent for different water levels: Flood maps Bonn (opens in a new tab)
Further information on the designation of flood zones can be found on the website of the Cologne district government: Determination of flood zones (opens in a new tab)
You can also determine your individual flood risk for your place of residence here: https: //bonn-unter.de (opens in a new tab)
Personal provision for emergencies
The city of Bonn takes its duty of care very seriously. It is the task of the municipal authorities to take structural measures to reduce flooding and damage. However, one hundred percent protection against flooding and flash floods cannot be achieved by the municipal infrastructure alone.
We therefore ask citizens to take all possible precautions themselves. What many people don't know: Self-precaution is even legally enshrined in the Federal Water Act (Section 5 (2) WHG). Find out whether you live in an urban area at risk of flooding.
Effective self-help and neighborly help is essential in the event of flooding. For new residents in particular, it is important to get advice on the local situation from neighbors with experience of flooding.
The following are general recommendations and tips for precautionary measures:
- Find out the critical flood mark for your house. You can enter your address at bonn-unter.de (opens in a new tab) and receive information on the flood risk at your place of residence.
- The following items are helpful as "basic personal equipment": battery-operated radio, off-grid emergency lighting, spare batteries, off-grid cooker, supply of clean (drinking) water, spare gas cylinder, rubber boots or waders.
- Seal windows and doors. This can be achieved effectively with simple mobile protection systems. These can be purchased from specialist companies. Seek advice on which individual solutions are suitable for your home. Sandbags are also effective, but ultimately they do not keep the water out completely.
- As a homeowner, ensure that oil tanks are properly secured against floating. You can find more information here.
- If your home is frequently affected by flooding, you should also have the following ready: Submersible pump, emergency generator, small boat, spare toilet.
- Do not store any valuable items in areas of the house or apartment affected by flooding.
- Do not use cellars that have been cleared out until the water level in them has dropped below the critical level of the Rhine.
- Secure your sewer house connection with a backwater flap against backwater from the sewer.
Building project
If you wish to build in a designated flood zone, please refer to the following pages for information on the legal basis.
- The Cologne district government (opens in a new tab) issues water law permits for the construction, modification or removal of facilities in, on, over and under bodies of water, as well as for projects that do not require a building permit in legally designated flood zones.
- Some streams in Bonn have also been designated as statutory flood zones. The lower water authority is responsible here: Flood zones
- For construction measures in flood-prone areas, please refer to the information on the website (opens in a new tab) of the Ministry for the Environment, Nature Conservation and Transport of North Rhine-Westphalia (LANUV).
Flood protection in Bonn
Due to their different elevations, Bonn's districts are affected by flooding to varying degrees. The flood protection measures have therefore been adapted to the needs of the different districts.
The civil engineering department of the city of Bonn is responsible for the planning and construction of flood protection facilities, while the fire department coordinates the construction of flood protection in the event of an emergency. Today, Rhine floods can be predicted two to three days in advance. You can find information on this at
Underground flood protection
What is usually not so well known is that the sewer network must also be protected against flooding. This prevents extraneous water from entering the sewer and ensures that wastewater can continue to be transported and treated in the sewage treatment plants. To this end, for example, the sewer outlets close to the Rhine are closed with gate valves, pumping stations are put into operation and manhole covers are sealed tightly. Underground flood protection in Bonn begins at a Rhine water level of 5.50 m Bonn level.
Above-ground flood protection
Flooding beyond the banks of the Rhine, on the other hand, is more of a focus.
Most of the buildings close to the banks are already adapted to Rhine flooding. Many buildings were erected on higher ground and flood protection walls were built, as can be clearly seen on the Rathenauufer on the left bank of the Rhine, for example. Large parts of the left bank of the Rhine were filled in in the 1950s in the course of the destruction caused by the war and formed into today's promenade. This also created a certain degree of flood protection for the districts close to the Rhine, such as the completely destroyed former old town area around today's opera house.
Following the floods of the century in 1993 and 1995, a flood protection concept was drawn up for the Rhine, in which flood protection measures were developed and have been implemented to date. Due to the different ground levels, more flood protection measures are necessary in some parts of the city than in others.
Bad Godesberg
The lowest area in the Godesberg district is located in the far south at the Bonn city limits in Mehlem. Here, a dyke prevents the Rhine floods from entering from the south. In addition, a number of mobile flood protection elements are being erected in Rüdigerstraße in Mehlem.
Beuel
Due to its deep location, Beuel is the district of Bonn most affected by flooding from the Rhine, as was clearly evident during the floods of the century in 1993 and 1995.
Dykes
Following the floods of 1993 and 1995, the dykes on the right bank of the Rhine, which were built in the 1930s, were renewed.
The Beuel-Nord dyke renovation, from Combahnstraße to the Beuel Nord highway junction, was completed in 2011. The dyke was raised and is now designed for a Bonn water level of 11.20 meters.
The Siegdeich dyke, which primarily protects against Rhine floods backing up into the mouth of the Sieg, was completely renovated back in 1993 and, like the Beuel Nord Rhine dyke, protects up to a Bonn water level of 11.20 meters.
Flood protection on the banks of the Rhine in Beuel
The upstream flood protection up to 9.50 meters Bonn water level along the Rhine promenade, from Werdstraße via Marienstraße to Ernst-Moritz-Arndt-Straße, was constructed in two planning approval sections, each with five construction phases between 1993 and 2011.
The compensatory measure for the loss of retention space due to the Beuel "Promenadendeich" was carried out on the Rheindorfer Bach in 2001.
Second line of defense
In order to protect the protection level, which was raised by one meter during the renovation of the Beuel-Nord dyke and now stands at 11.20 meters Bonn water level, from a backflow from the south, a second line of defence was required.
A mobile flood protection wall in the middle of Professor-Neu-Allee prevents the Rhine water that would otherwise enter via Combahnstraße from flowing behind the dyke. In order to prevent underground drainage via the sewage system, a second sewer was built that can be disconnected in the event of flooding. Further down Hermannstrasse to Johann-Link-Strasse, another mobile flood protection wall will prevent the Rhine floodwater from entering behind the dyke into the low-lying areas of Schwarzrheindorf and Limperich.
The mobile flood protection will be erected when the flood forecast indicates that a water level of 10 meters Bonn gauge, with a rising tendency, will be reached.
Graurheindorf
Flood protection is also to be built on the banks of the Rhine in Graurheindorf.
In the event of a flood, the Rhine overflows its banks on the one hand, and on the other, a backwater occurs at the mouth of the Rheindorfer Bach in the middle of the village. In order to protect Graurheindorf from Rhine floods of up to 9.50 meters Bonn level, existing embankment walls are to be reinforced and supplemented to protect the buildings near the banks. The prerequisite for flood protection on the Rhine is the relocation of the mouth of the Rheindorfer Bach to the north, near the Mondorf ferry.
The current mouth of the Rheindorfer Bach is to be closed, as the greatest flood risk for Graurheindorf is the Rhine floodwater pushing back through the course of the stream into the town center.
The stream relocation project is currently in the planning approval process. If this is approved, the planning approval for the construction of the flood protection on the Rhine can begin.