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On this page you will find frequently asked questions and answers about the measure and tree felling.
1. why does the Main dyke need to be extended?
The Main dyke is designed to protect against flooding. The Darmstadt Regional Council stipulates that a dyke must be able to withstand a flood level that statistically occurs every 200 years. The municipal dyke sections do not yet meet this requirement.
2. how is the removal carried out?
The expansion of the urban Main embankment was divided into three sections with a total length of around 2.6 kilometers. The sections are located in the city center (section 1) and in Rumpenheim (sections 2 and 3). The state of Hesse is responsible for the second section (Bürgel).
With the exception of the third section (field location in Rumpenheim), the dyke function is ensured by sheet piling. In the second section (Rumpenheim district), these have been clad with sandstone. In the first section (inner city), the sheet pile walls are hydraulically pressed into the existing top edge of the embankment and have to be anchored back on the road side with the help of ground anchors. The reason for choosing this construction method is to protect the existing buildings (e.g. the canal in Mainstrasse and the pipeline routes in the area in front of the Main). This construction method also means less noise.
3. when will the expansion begin and how long will the construction work take?
Construction work on the second and third sections in Rumpenheim has already been completed. The felling work for the first construction phase in the city center took place in November 2025. Actual construction work will begin in fall 2026.
4. do trees have to be felled to extend the Main dyke?
Yes, in order to guarantee flood protection, some tree crowns have to be cut back and 190 trees have to be felled completely. The above-mentioned sheet piling with tie-backs is unfortunately not possible otherwise. An alternative construction method was tested and had to be rejected. Once the construction work has been completed, a new tree will be planted for every tree felled on the dyke crown path.
5. was it not possible to prevent the tree felling?
As part of the planning process, various measures have already been taken to prevent tree felling. All options were examined individually for each tree. Nevertheless, not all trees could be preserved. The installation of the sheet piling and various underground measures to provide structural support for the walls meant a massive intrusion into the root area of the trees, meaning that it was not possible to preserve them.
6. have you considered transplanting the trees?
The transplanting of large trees is extremely complex and involves considerable costs. Due to the technical circumstances, only the central root area, with a diameter of around 3.0 meters, can be taken over. In order to reduce the tree's water requirements, it is also necessary to cut back the crowns accordingly. In the case of the old trees on the Main dyke, many of which were already more or less severely damaged and already had reduced vitality, there was a particularly high risk that pruning in the heavy branch area would create potential weak points, which are a gateway for wood-decaying fungi. This can significantly reduce the life expectancy of a transplanted tree compared to leaving it in its original location. Against this background, and weighing up the cost and effect, this approach was not pursued further.
7. will the trees be replaced?
Every single tree on the dyke crown path will be replaced after the work and supplemented by further tree planting, so that there will be more trees on the dyke afterwards than before. A total of 167 new trees will be planted on the Deichkronenweg. The trees to be felled in the area in front of the Main to the east of Friedhofstrasse will not be replaced because more backwater volume for the Main needs to be created here in the event of flooding.
8. which tree species will be replanted and how much shade will they provide?
In consultation with the Darmstadt Regional Council, various tree species were selected for the new planting, including lime trees, oaks, maples and hornbeams. During the selection process, particular attention was paid to the suitability of the species for this location.
The size of nursery plants is defined by the so-called quality and measured by the trunk circumference, among other things. For the new planting of the 167 new trees on the Main dyke, the trunk circumference was set at 20-25 cm as part of the approval process, which corresponds to the usual qualities for new plantings in the city of Offenbach. The height of the trees with this trunk circumference varies depending on the tree species and averages around 4 to 5 meters.
Compared to the existing tree population, the shade cast by the newly planted trees is initially significantly lower, as the branches in the crowns still have to be pruned back slightly after planting, but will increase significantly over time as a dense canopy of leaves develops. Depending on the tree species, the trees will grow approx. 35 cm per year in height and approx. 30 cm in width. A total of 72 old trees can be preserved on the dyke crown path and will continue to provide larger shaded areas.
9. what will the footpaths look like once the construction work is complete?
Terraces for lingering and relaxing, a barrier-free staircase on Herrnstraße with a combination of stairs and ramp and an optimized dyke gate on Schloßstraße are being created.
10. how is the city of Offenbach using the expansion of the Main dyke to improve the quality of life in addition to flood protection?
Terraces, more seating and opportunities to play chess and "Mensch ärgere dich nicht" are intended to make the area on the dyke more attractive for residents.
11. is noise or restrictions for residents to be expected during the construction period?
Citizens must expect traffic restrictions during the construction period. These will always be communicated in good time. Noise must also be expected. By deciding to hydraulically press in the sheet piles instead of driving them in, an attempt was made to keep the noise as low as possible.
12. will there be disruptions to road traffic?
Major disruptions must be expected on Mainstraße. A one-way street from east to west is planned. The northern carriageway will have to be closed as far as possible. The time periods and exact traffic information will always be communicated in good time.
13 What are the consequences for pedestrians and cyclists?
The embankment itself will not be accessible during the construction period. With the exception of a short detour at the Innovation Campus site, cycling will be possible throughout the area in front of the Main.
14. will there be no parking spaces during the construction work?
The construction site area will take up about a third of the parking lot at the Carl-Ulrich Bridge, all other parking spaces on the banks of the Main will remain available.
15 Was there public participation?
Yes, a multi-stage participation process took place in 2011. Click here to go directly to the information page.
16 Where can I get regular updates on the progress of the expansion?
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The official text is the German version of the website. If you have any questions about the accuracy of the information contained on the translated website, please use the German version of the website.
