The floods have highlighted the problems posed by waterproofing and the importance of designing “sponge cities”.
This concept designates urban areas designed according to integrated rainwater management, in order to buffer floods and limit the damage caused by flooding.
The design of a sponge city requires implementing a set of alternative water management techniques: swales, water gardens, infiltration trenches, etc.
It also involves the use of coverings that are more or less permeable to water, such as paving stones with porous or grass joints.
An obstacle that is often presented is the fact that porous coatings negatively impact circulation and accessibility (cyclist, automobile, horizontal, etc.).
In Germany, the city of Berlin constitutes a perfect example of compromise between traffic constraints and the implementation of largely permeable surfaces (image).
The parking spaces are paved with porous joints (bottom), while the sidewalks have a paved path in the center for bicycle traffic, bordered on either side by smaller paving stones (top).
We often praise the “German model”, but it must be recognized that Berlin is an exemplary sponge city in terms of soil treatment.
There is even a German term, “Schwammstadt”, which literally translates to “sponge town” in French.
As this example shows, a sponge city is not necessarily spectacular!
Sources: T. Maytraud, C. Piel, J. Chaïb
Image: C. Gaillard