Sponge Cities

Urban development for a changing climate

Many of us don’t have to look at a century’s worth of records to realize dramatic weather events are starting to become more frequent in our generation’s lifetime alone. This phenomenon has a lot to do with climate change, but beyond pollutants, it has to do with the way we’ve developed our societies. Large cities with no room for nature to adapt are continually finding themselves fighting against nature to survive.

Architects across the globe are finding the battle exhausting and have thought of a new way for cities to thrive. Instead of fighting against encroaching nature, we could try living in harmony with it. By working with nature, we can all handle weather and climate change more efficiently, instead of fighting a pointless war that could wipe out both sides given enough time.

One of the ways architects are already handling the issue is with sponge cities.

What Are Sponge Cities?

One of society’s most significant threats from the changing weather is flooding. Areas thick with concrete and other impermeable materials — cities — are prone to floods during big storms because there is nowhere for the water to go. Gray infrastructures such as floodwalls and human-made drains can handle some amounts of water, especially when floods are due to rising water levels in local rivers, but they can rarely handle sudden floods.

A sponge city more or less makes existing urban regions absorbent. These unique cities implement natural materials into their architecture to soak up rainwater, instead of allowing it to flood areas. The absorbed water seeps underground, allowing people to create intra-city wells.

Since groundwater is easily treatable, this also solves the problem of depleted water resources within urban areas. By building with nature, we can stop floods, have more clean water, cause less pollution in our drainage systems for oceans, and create more green areas in urban ecosystems.

There are a few things a city needs to become a sponge city and provide all this aid to the area. First, they must stop or slow down expansion with concrete and asphalt to build more open green areas. These can be in the form of waterways or ponds, areas that won’t encroach on people and businesses, but that are also not hard to implement.

Some roofs, such as green roofs, can also retain rainwater and filter it before it even reaches the ground. Mostly, though, using more porous materials and designs will be the best advantage a city can have.

Developments in China

China is the first country to implement flood prevention policies in the form of sponge cities. The idea was initially developed by Professor Kongjian Yu, stemming from his work in landscape architecture at Harvard University and his desire to tackle flooding issues in Chinese cities.

Over the past 20 years, sponge city architecture has grown across the country. After widespread flooding in Beijing in 2012, they began launching sponge cities in 2015 in 16 locations. Soon after, they extended these 16 model cities to 30 to include Shanghai.

Their goals for Shanghai include 20 percent of each pilot district to absorb or recapture 70 percent of rainwater by 2020. By 2030, China wants 80 percent of each city to meet the same numbers.

China is meeting these demands by giving the land back to nature. After a terrible flood in 2016, the city of Wuhan has been meeting the standards by rebuilding the lakes they’ve previously destroyed for urban development and creating porous infrastructure in public spaces. In Wuhan alone, costs to retrofit over 38.5 square kilometers have totaled 11 billion yuan, the equivalent of $1.5 billion.

How Other Countries Can Benefit

Flooding isn’t just an issue in China. Other countries, particularly the United States, Russia, and India, have started looking at sponge cities as a possible solution. Urban centers suffering from both water scarcity and flooding are seeing potential in the natural systems this architectural style helps develop.

India’s quickly growing cities, for example, suffer disastrous consequences from flooding. In 2017, monsoon rains devastated parts of South Asia, resulting in more than 1,200 deaths. Part of the problem is that urban centers like Mumbai were built on wetlands, disrupting the previous natural pattern.

The US West Coast, especially, has seen a lot of problems involving water, with periods of droughts and floods shifting far too quickly. California alone has lost 350,000 acres of land to urbanization since 1990. In this quickly developing area, cities built to sustainably manage rainwater could be a huge boon to both the environment and the local population.

Access to water and old infrastructure remains a challenge for nations — regardless of their economic power. But even richer countries struggle to adapt their urban centers for sustainability. With so many regions worldwide suffering from the pitfalls of urban development, why haven’t sponge cities taken more of a center stage?

Challenges Remain for Sponge Cities

There are many reasons other countries aren’t pushing for sponge cities right now, but the cost is the most significant factor. In America, much of the infrastructure already needs updates, so the price tags would likely be more per city than what China has had to spend. Beyond money, though, there are a few technical problems.

First, there are logistical and bureaucratic barriers that prevent such widespread changes from being implemented. This has been a major obstacle for China despite its ambitious goals for water management. And in any city, the union of public interest, private property, and slow-moving legislation means architectural change is difficult to achieve.

There are also environmental concerns. Professor Guan Yuntao, director of the Research Center for Environmental Engineering and Management, explained a major vehicle accident with a tanker could result in an oil spill. Instead of our current ways to handle this waste, the oil could seep into the ground with rainwater and pollute the entire city’s drinking water. Civic leaders must consider these and other eventualities before widespread implementation of sponge cities.

Can Sponge Cities Be the Future of Infrastructure?

Most likely, many cities are going to go back to what they were before urban development got out of hand. If done correctly, bringing in more nature or building around existing green space shouldn’t infringe on people and their livelihoods.

However, ensuring the work takes place with no snags will take a lot of research, money, and time. Other countries likely plan to watch and learn from what China is doing before taking the initiative.

Written by: Holly Welles, BOSS Contributor

Holly Welles is a real estate writer who covers the latest market trends in everything from residential to commercial spaces. She is the editor behind her own blog, The Estate Update, and curates more advice on Twitter.