What can be done to allow a maximum of rainwater in cities to evaporate decentrally?Today most rainwater from city streets is fed into the sewer system to protect trees and ground water from road salt and other contaminants. How can more of this water be brought to evaporation and remain in the natural water cycle?
Because rainwater from city streets is often charged with road salt (in winter) and other contaminants, it is mostly fed into the sewer system. Therefore, - and with heavy rainfalls becoming more frequent and intense due to climate change - large public investments are needed to maintain adequate capacities of the sewer system. On the other hand city trees often lack water during hot and dry summer periods. Retention and evaporation of rainwater could benefit city trees and reduce the urban heat effect, thereby contributing to climate change adaptation.
Solutions to these conflicting targets should focus on:
- Improving growing conditions for trees on streets and in the city in general
- Avoiding saline intrusion into the groundwater (in winter)
- Retention of rainwater in case of havy rainfalls to reduce the load on the sewer systems
- Increasing evaporation of surface water to reduce urban heat effects
- Innovative systems for the separation of winter and summer surface water (constructional, technical, with the help of IT solutions, etc.)
This challenge is hosted by the City of Vienna, Environmental Protection Department (MA 22). Innovative solutions to this challenge could be tested in pilot projects and become standard for road planning.