The plant life along the bridges is supplied with water by the bridge and enhanced with new plantings

All plants directly at the bridge can be strengthened both in the course of the construction work and afterwards. In this way, beautiful green areas of high quality for nature are created along the entire length of the route, which can also infiltrate rainwater that accumulates!

Content: Describes measures taken during the construction and operation of the Frankfurt bridges to enhance the urban green space to either side.

During the construction work, the green areas along the bridges will be restored and upgraded by replacing polluted urban soil, pruning trees and plants, and planting new plants appropriate to the site.

After completion, the most important levers for maintaining these vitalized areas are that the Frankfurt bridges provide continuous irrigation as needed with the appropriate supply of nutrients. In addition, optimal tree and bed maintenance for the flora along the bridge can be ensured by the bridge gardeners.

The new bridge greenery to be planted must be professionally planned and executed to provide permanent noise and visual protection for residents and walkers.

The flora to the right and left of the bridges is supplied by the water of the bridge ring pipe and cisterns under the bridge - therefore it becomes more lush and dense than before!

A ring main runs in the bridges, which not only supplies the plants on the bridge, but is also tapped every 50 to 100 meters for the plant life along the bridges. In addition, cisterns are laid in the ground under the bridges that could collect rainwater from the bridges as well as roof rainwater from the adjacent roofs. They, too, water the greenery directly at the bridge when needed.

About 8000 trees are located along the planned route of the Frankfurt bridges: They are thus directly affected by the construction of the bridges

However, no vital tree along the bridges is to be felled or damaged in the course of the construction measures. On the contrary, the construction project can be used as an opportunity to create better living and growing conditions for the trees.

This is because part of the asphalt is removed for the construction of the bridges, so that the soil, which has been compacted over the years, can be extensively vitalized and trees made healthier and more resistant.

Urban trees are, as forestry scientist Peter Wohlleben says, the street urchins among trees. They have learned to fend for themselves under the most adverse conditions and to cope with the meager, sometimes toxic nutrient supply of urban soil, which is heavily polluted by tire abrasion and the use of road salt - even from decades past.

Many of Frankfurt's urban trees have therefore been struggling with the adverse conditions for years. Many damages to trees are already visible to the expert and the death of the trees seems to be only a matter of time.

Even in the urban forest, only 3% of trees were vital after 2019.

Construction measure as "wellness cure": Trees weakened by city life are vitalized in the course of the construction measures

Usually, construction measures are more of a danger for urban trees and not an enrichment. A unique paradigm shift is to be made when constructing the Frankfurt Bridges: The construction measures should not only include the prescribed minimum consideration for urban trees, but should integrate their vitalisation as a target component in their planning from the very beginning.

Before starting to build the bridge on a section, it is necessary to analyze the soil underneath and the course of its roots for each older tree. Only then can improvement of the growing conditions be targeted: Soil aeration, soil replacement, adapted nutrient and water supply or even pruning are among the most important measures here.

Standortverbesserung - janssen-landschaftspflege.de

All trees along the bridges should not only be preserved, but also strengthened - so the bridges become lush treetop paths at the same time

Cutouts are provided for each tree along the surface of the bridge. By pruning the tree, the crown unfolds only above the bridge, so that the bridges are framed by the building crowns. The cutouts are sized large enough and the trees are professionally pruned so that no damage occurs to the bridge or tree in the event of wind.

The pruning of the trees should already be started in the years of preliminary bridge planning

The cutouts in the bridge surface allow all trees along the Frankfurt bridges to develop naturally as far as possible. If, however, things do get tighter, trees can also adapt to the structural environment with professional pruning. However, this is not necessary along the bridges to the extent that it is found everywhere in the city.

Trees are true adaptation artists

They even manage to "dodge" obstacles, as can often be seen in the street scene.

However, this is to be avoided along the bridges: by the circular recesses, which are dimensioned according to the tree species and the spacing of the trees next to the bridges.

Especially in the old tree-rich neighborhoods of the city, trees had to come to terms with houses

Who uses the space under the sealed surface? Pipes and cables often compete for the same space as tree roots

Root scans are used to check the exact spread and course of the tree roots in advance of the construction work. This enables the optimum position of the bridge piers to be determined: This is because the structural system for the bridges is already designed so that each pier can be moved at least one meter to the right or left. This means that in many cases the main supply roots of trees can be avoided.

Nutrient and water addition are effective and easy to implement measures to vitalize trees

Poor nutrient supply causes yellowing of the trees. Through proper fertilization and adequate watering receive the significant revitalization, which is reflected in much greener foliage.

Experts on the Topic

Institut für Stadtgrün — NABU-Landesverband Berlin Stadtgrün schützen — Universität Hamburg Institut für Bodenkunde

Greenery as visual and noise protection: especially for residents

In the course of the redesign, it is also possible to hide car roads: in the green areas between the columns of the bridges, lush beds with taller bushes will be replanted after the construction work.

In the process, the plants not only improve the air and provide further coolness; above all, they also hide what today characterizes the cityscape in those places: the gray asphalt of the street and the passing cars.

Thus, they serve as visual, noise and exhaust gas protection for the people living nearby.

GOOGLE EARTH Stiftung Altes Neuland Frankfurt GNU

Walkers on grass verges between motorways also benefit from the new visual and noise protection

The Frankfurt bridges create the conditions for such "plant walls" to emerge in the city: Through them, water can be transported to planting strips along the streets that were previously left to themselves.

Currently, roadside greenery is often monotonous and sparsely planted. The bridge greenery, however, will be consistently varied and lush

The challenge here is a differentiated site-specific bed planning that takes into account sunlight, temperature, water, pH, nutrient concentration, climate, relief of the site. This can ensure that a permanent planting can be established there.

The green areas along the Frankfurt bridges are planned in advance with beds adapted to the location - in shade, partial shade and sun are the most important factors here

Planting plan and aspect calendar of a roadside evergreen semi-shade bed

Planting plan and aspect calendar of a shady forest bed on the roadside

Conclusion: The Frankfurt bridges as a construction project let the existing green spaces and trees along the bridges become more lush and vital

While a construction project usually tends to harm the plant world or even cost trees their lives, the exact opposite is the case with the Frankfurt bridges. Existing green spaces are planted more lushly, vitalized and expanded.

The trees along the bridges are integrated into the structure and vitalized by the structure in such a way that magnificent treetop paths are created.

The quality of stay for residents and walkers is significantly increased by the noise and visual protection provided by the more lush and varied street greenery.

Greenery on the bridges

Nature conservation and biodiversity

Unsealing of the city center

Vitalization of the urban greenery

The green metropolis of the future

The goal: to arm the city against drought and floods

Water distribution with the bridge-ring-line

Frankfurt: Current urban climate