How does a “sponge city” work?
In the early 2000ies, Western and Northern European cities faced heavy rainfalls causing huge damage in the dense urban fabric. Since then, new housing estates have been built in frontrunner cities without using grey infrastructure to collect rainwater, and water retention has been an integrated part of urban development. We explain the key lessons and challenges since droughts experienced in the last years almost everywhere in Europe make the theme more essential than ever.
“Extensive green rooftops (made up of a very thin - 8-15 cm - layer of substrate with shallow-root and resistance plants like sedum, herbs, mosses, and grasses) can absorb 70-80% of the rainwater, it protects the roof and boosts its insulation capacity - thus we created our Botanical Roof Garden, one of the biggest green rooftop complexes in Europe, on the rooftop of the communal utility company, to promote different techniques” - says Ms Helen Johansson, director of the Green Roof Institute during a study visit organised in the frame of the URBACT Summer University (2023).
