Sponge Cities

A huge consequence of climate change has been both increased flooding and increased drought in vulnerable cities. These are caused by unpredictable extreme weather events and leave cities struggling to adapt to unstable climate conditions. Other issues related to climate change have included the diminishing groundwater supply that results in less water availability for consumption as well as excess amounts of polluted water. In times like this, where urban and suburban expansion don’t seem to be stopping any time soon in an effort to accommodate that rapidly increasing population, innovative yet regenerative solutions are necessary to make our cities less climate-impactful. One of those possible solutions may be sponge cities. 

Sponge cities are almost exactly what you may be thinking–they are designed to absorb water like sponges. Cities are full of impervious surfaces like asphalt and concrete. So the increased amount of rainfall due to extreme weather events means more runoff from these surfaces, which may cause a lot more urban flooding. Our current drainage systems are unable to absorb and direct this much water moving through, which is why sponge cities may be a perfect strategy to increase our cities’ capacities to deal with increased rainfall. 

Creating a sponge city consists of implementing a number of technologies–essentially, it means introducing more green spaces into urban areas. These include green roofs, green facades, and swales, which are sunken green areas with a permeable soil layer, acting as shallow drains, much like a rain garden! What is great about sponge city technology is that it blends into the rest of the city design, even enhancing it with more green spaces. Increasingly, sustainable options are also becoming options that are a good choice aesthetically and equitably. Adding more of these green spaces to different parts of urban areas creates more equitable access to green spaces.

Building sponge cities encourages more water drainage through permeable surfaces, lessening the burden on our industrial drainage systems. Green spaces with plants and soil filter stormwater naturally, providing us with clean water in a time where its availability is shrinking. The increased plant and water presence will decrease the impacts of the urban heat island effect, where cities experience a significant difference in temperatures compared to more rural areas. Additionally, biodiversity in cities will increase with all of the new plant species. 

The idea of the sponge city first rose in China, where it was first brought into action in 2012 after urban flooding in Beijing. It has been implemented frequently throughout cities in China, as well as some in Europe. There is even a sponge city project happening in the South Thornton neighborhood of Seattle. Cities are beginning to catch on to how useful sponge cities can be to offset the effects of the climate crisis, but municipal and state governments need to make significant efforts to fund these projects for them to make a widespread impact.

Written by Carmen Marshall ‘ 25

Photo by Obermeyer