Roosevelt Institute | Cornell University

Draining the SpongeHow Flood Control Measures Pioneered in China Can Fortify NYC Against Climate Change

By Michael DekhtyarPublished August 20, 2021

Cheonggyecheon, a public green space and urban renewal project in downtown Seoul, South Korea.
New York City's aging flood-control and drainage infrastructure is cracking under pressure from climate change. Applying the Chinese concept of "sponge cities" to future development can fix that.

Decades of gridlock, mismanagement, and administrative turmoil have left New York City’s flood and storm infrastructure in a state of serious disrepair. Nine years after Hurricane Sandy, which in 2011 flooded entire neighborhoods and submerged busy streets in several feet of water, the city government has yet to implement serious, permanent improvements to NYC’s flood control system. 

Experts and policymakers agree that NYC’s storm protection deserves an upgrade, but they are split on what form it should take. The proposed Storm-Surge Barrier​​a massive six-mile-long sea wall meant to provide protection from storm-induced floods across NYC and Jersey Cityhas yet to begin construction. In fact, key federal funding for the project, which was projected to cost around $62 billion in total, was suspended by the Trump administration earlier this year. Even if it overcomes these hurdles, the Storm-Surge Barrier faces numerous financial, legislative, and regulatory burdens in its current developmental state and, by many accounts, its creation seems a long way off. 

In any case, it’s clear that NYC’s existing infrastructure is no longer capable of dealing with increasingly frequent and intense storms and floods. “Sponge cities,” pioneered at scale in China, provide a possible solution. In the event of floods or torrential rains, sponge cities are designed to recycle huge amounts of water into the natural environment in an efficient and sustainable way. 

The “sponge city concept” in China was first proposed by Peking University’s Professor Kongjiang Yu, who envisioned the idea as a way to unite man-made technology and methodology with natural processes. Sponge cities are heavily reliant on combining typical features of urban centerstall buildings, complex drainage systems, and housing sprawlwith sustainable technologies that utilize these factors in environmentally friendly ways. Professor Yu argues that constructing green spaces like parks, planters, and rooftop gardens, as well as replacing concrete and asphalt lots with permeable pavement (which recycles and redirects excess rainwater), would allow cities to absorb a much higher percentage of rainwater and floodwater.

New York City is uniquely positioned to benefit from the growing popularity of sponge cities and has the ability to do so in a sustainable and financially sound manner. Significantly increasing the amount of green space, gardens, trees, and planters throughout the city would be a reasonable place to start, as nothing absorbs rainwater better than vegetated or grassy soil. In densely populated or constructed areas where building out large tracts of green space is not possible, constructing more bioswale planters would be a cost-effective (and aesthetically attractive) move. Populating sidewalks and streets with vegetated planters that efficiently absorb rainwater and beautify the “concrete jungle” of the city would be a crucial step in reinforcing New York’s water infrastructure. Finally, proliferating already-common rooftop gardens across more buildings throughout Manhattan would boost the densest borough’s sustainability while changing relatively little about its real estate.

In the face of the devastating COVID-19 pandemic, New York City’s government must be prepared to launch an environmentally sustainable economic recovery program. Incorporating elements of the “sponge city” concept into NYC’s infrastructure are vital to any such effort. There will inevitably be significant challenges to such a large-scale implementation, but if New York City aims to effectively prepare for a future of intense and frequent floods, rains, and storms, the sponge city concept presents a workable solution.