Heat and drought caused by global warming are taking their toll on trees in the city. The "sponge city" principle also gives roots more space under streets, parking lots and side-walks.
Where, if not in the "lake city," is it appropriate to think about how to deal with rainwater and improve the microclimate. Therefore, it is not surprising that an experimental field for the city of tomorrow is also being opened here. The "sponge city" principle ensures that trees have an adequate supply of water, even in very hot weather and long periods of drought. The larger root space also results in a larger tree crown.
This is made possible by an ingenious system in which sufficient gravel bodies are created below the paved surfaces in the road space to store rainwater:
Rainwater is stored and retained and is available to the trees for longer periods. At the same time, flooding during heavy rainfall events is mitigated or prevented. For this purpose, a layer of coarse-grained gravel as well as finer, water-storing materials is laid beneath the paved surfaces in the road space. The trees stand in their tree grates as usual but have direct contact with the gravel layers and can root through them. Rainwater can also run off directly into the tree disc or into the gravel layer via inlet shafts and drainage facilities. It is thus available to the tree in sufficient quantity and over a correspondingly longer period of time.
Since the application of this project under the climatic and meteorological conditions of this magnitude has not yet been tested in Vienna, the implementation represents an experiment that will be scientifically accompanied and evaluated.