Flowering Infiltration Swales in Urban Areas

Rapid urbanization is leading to high levels of densification in cities. The resulting increasing soil-sealing and reduction of inner-city green spaces inevitably leads to changes in the local water balance, intensification of effects such as the urban heat-island and a decline in biodiversity in residential areas. The climate change promotes more frequent extreme events such as heavy rainfall and drought periods and therefore, intensify the negative effects of missing open spaces in cities. Green, flowering infiltration swales are considered to be particularly promising ways of counteracting these challenges.

The aim of the interdisciplinary research project was to investigate the benefits that can be achieved in an urban infiltration swale through species-rich, native planting and an adapted substrate composition. In addition to the stress tolerance of the vegetation, drainage saftey, pollutant retention and insect diversity were investigated. At the Chair of Urban Water Systems Engineering, the pollutant load and stability of the infiltration swales were investigated on a semi-technical scale by feeding them with real traffic area runoff. In addition, pilot swales on a heavily trafficked road in Munich were monitored and the retention of heavy metals was analyzed. The risk of siltation of the topsoil in long-term operated infiltration swales was examined in Freiham and further, the accumulation of pollutants was evaluated regarding the soil-human impact pathway (in accordance with the BBodSchV). The one-year research project was successfully completed in December 2024. In the preceding research project on multifunctional infiltration swales, the publication "Multifunktionale Versicherungsmulden Handlungsempfehlung zu Planung, Bau und Betrieb" was published by the Bavarian Environment Agency (LfU) in September 2024.