The receding concretization in an increasing number of Polish cities makes it possible to give back to greenery the places previously occupied by asphalt and paving slabs. Increasingly, green spaces and flower beds with diverse vegetation are appearing along roads and sidewalks. But what if there is no more room to take off the sidewalk, and the growing trees no longer fit into the designated sidewalk meshes? Work is underway to solve this problem.
Sidewalk protecting trees
The Warsaw Greenery Board is working on a project for tree-friendly sidewalk surfaces. The project is being carried out in three stages - in the first a report was created summarizing the problems of anthropopressure (the impact of human activities on nature) and the legal conditions for the construction of traffic routes in Warsaw. The document diagnoses issues related to the development of the root system of individual plant species, the problem of the destructive impact of the development of the root system on pavements, the requirements for water and gas permeability of pavements in relation to the demand of plants, the type of plants preferred for planting in the city, the distance of the designed pavement from, for example, the trunk of a tree. The report was based on the cooperation of city units and the Road and Bridge Research Institute, and the final version was developed by a team of construction experts led by Professor Barbara Rymsza.
for years
photo ZZW
As far as newly planted trees are concerned, there are many solutions to enable the development of the root system, but making pavements next to old trees that will not unduly affect their proliferated root system requires designing non-standard solutions. By creating a catalog of tree-friendly sidewalks, the Warsaw Greenery Board wants to resolve the conflict between the newly designed or renovated sidewalk and the existing root system. Good condition of trees is ensured by a healthy root system, which requires proper conditions for development. It is estimated that 90% of the roots are at a depth of up to 60 cm. For root development, oxygen is needed, which is in short supply in heavily amended and compacted road lane soils, often covered with bituminous pavement. For this reason, most of the roots that nourish the tree develop as deep as 10-15 cm below the soil surface.
artificial resin and minerals
Mineral pavements have been used in Krakow Park, among others
Mineral-resin pavements are a material increasingly used for their permeable properties. They are most often gaining use in parks, due to their still limited load and use potential. Similar to traditional aggregate pavements, they permeate water and allow it to be retained in the ground. Their appearance is natural and they blend in with the landscaping, and they also allow any geometry of alleys. Unfortunately, they also cause usability problems - including snow removal and cleanliness. The resin-mineral mixture also makes the product not easy to recycle.
Water-permeable concrete
Photo: Tredje Natur
A solution that can help in spaces that need to remain paved is the Climate Tile paving slab, designed by Denmark's Trejde Natur. It is actually a complete set of finishing elements for public spaces. The system allows water to be absorbed in heavily built-up city centers that lack free green spaces, and has been piloted in Copenhagen. The perforated panels are designed to restore the natural circulation of water in tightly paved and asphalt-covered urban spaces, thus feeding the trees growing in the area and relieving the pressure on storm drains. This functioning of the system is made possible by designed reservoirs, perforated plates and control units that collect or redirect water to other locations based on available data, an additional feature is the recognition of water with high road salt content in winter to protect plant roots from excessive salinity. The entire system is built in such a way that it can be implemented on sections of streets, but also easily expanded with additional modules. The dimensions of the slabs are based on the paving slabs used in Denmark, which allows the appearance of the sidewalks to be maintained and the scope of repairs to be limited.
Photo: Tredje Natur
