It’s not news that there’s a great disparity hanging over the United States. No, I’m not talking about the growing economic gap (that’s a larger issue that I’m not willing or qualified to tackle). What I’m referring to is the juxtaposition displayed on almost every news outlet between California’s drought and the recent flooding in central Texas. While Californians clamor to conserve water through the worst drought in 1200 years, Texas has been devastated by deadly flooding that destroyed homes and natural habitats alike. It’s hard not to wish there was some way to tip the scales and balance things out. But how?
China recently announced a new program they are calling the “Sponge City” project after noticing strikingly similar patterns to what the U.S. is currently dealing with. According to a recent dispatch in Frontiers in Ecology and the Environment written by Ganlin Huang, 62% of Chinese cities surveyed by the Ministry of Housing and Urban-Rural Development experienced one or more floods between 2008 and 2010. At the same time, two-thirds of China’s municipalities are experiencing water shortages. Kind of rings a bell, doesn’t it? So China has decided, rather than treating these issues separately, to recognize both crises as symptoms of the same issue. The result is one project that has shown promise in helping both drought and flood areas.
The idea behind the Sponge City project is to use absorbent surfaces, like green rooftops and porous pavements, to collect rainwater that would otherwise flow off hard city surfaces and into underground sewage systems. The “sponges” can then be “rung out”, so to speak, which allows for more direct and efficient use of water resources when they are needed. Huang’s article even notes that a successful pilot project in a part of Shenzhen City resulted in 70% of water that would normally end up in sewers being retained and reused, simply by installing green rooftops. China plans to try out the program in sixteen cities across the country for three years.
This project comes with a lot of other benefits because green rooftops aren’t just good at collecting rainwater. Proponents of green rooftops have suggested a number of ways in which they can help the environment and our cities. Unlike concrete or clay, they can sequester carbon, which is critical in mitigating the effects of increasing global carbon emissions. They provide habitat and food for beneficial organisms like honey bees. Some sources suggest that green rooftops can increase urban biodiversity and aid in conservation of rare species, although these claims are largely untested. Another advantage is that green rooftops improve air quality by filtering out various pollutants depending on what kind of plants you grow. There are also a number of more direct benefits including incentive programs that provide tax credits for installing green rooftops and lower energy costs that result from their insulating effects.
Photo of a green rooftop from papertastebuds.com
Whatever the primary motivation for installing green rooftops, it’s clear from the preliminary results of China’s Sponge City project that they and other permeable surfaces will be hugely beneficial in dealing with many of the extreme and unbalanced weather events occurring across the world. The United States and other countries should take note because, although it’s not a perfect solution, it seems like this project is headed in the right direction.
