If You Don’t Already Live in a Sponge City, You Will Soon

Water is great in moderation, but it can flood streets and homes if it rains too much. Climate change is bad at moderation. Municipal sewer systems were built for the climate of long ago and can be overwhelmed by storms that dump more water quicker. From Zhengzhou, China, to Seoul, South Korea, to Cologne, Germany, to New York City, there have been biblical floodings.

Urban planners are now thinking of cities less as rain jackets and more as sponges. Sponge cities are using rain as an asset to be exploited instead of expelling it.

Michael Kiparsky is the director of the Wheeler Water Institute at the University of California, Berkeley. The impact of climate change is getting worse because denser cities use more impervious surfaces. The lack of natural absorbency of large areas of soil and vegetation makes water problems worse when the capacity of these structures is exceeded.

Green spaces have traditionally been used for public enjoyment. They're used as a tool for managing rainstorms. In places like Pittsburgh, Pennsylvania, where storms have gotten significantly wetter over the past 50 years, an inch of rain dumped over an hour is more likely to overwhelm the infrastructure than the same amount of water falling over 24 hours. The long and short of it is that it is more intense and frequent. There is a lot of work going on in Pittsburgh and the mid-Atlantic to look at those numbers in the future.