After the first El Niño fueled rainfall landed across California a few weeks ago, concerns about potential flooding across Los Angeles neighborhoods became a popular topic of discussion. Friends, coworkers, and neighbors shared tips for preparing for future storms or floods, recognizing this year’s El Niño had the potential to be one of the strongest on record (though the recent mild and warm weather are a deceptive respite). And when it comes to its peak this February and March, Californians have been trained to expect “mudslides, heavy rainfall, one storm after another like a conveyor belt.”
Despite the El Niño rain expected to hit Central and Southern California by the end of this month, the drought will remain in effect according to the U.S. Drought Outlook. With Los Angeles expected to grow in size and population in the coming years, the threat of the cycle between extreme weather like El Niño and the drought becoming the norm seems reason enough for the city to review and replace its outdated and single-use grey water infrastructure system with something greener and more water re-use efficient. We can look to China for possible solutions.
What is a “Sponge City”?
Since 2008, the number of Chinese cities affected by flooding has more than doubled. Conversely, severe and extreme droughts have also become a serious nationwide issue since late the 1990s.
“The rate of flooding is a national scandal,” said Kongjian Yu, the dean of Peking University’s College of Architecture and Landscape Architecture. “We have poured more than enough concrete. It’s time to invest in a new type of green infrastructure.” Sounds very familiar and similar to the challenges we’re facing here in Los Angeles.
China’s solution? Sponge City.
“A sponge city is one that can hold, clean, and drain water in a natural way using an ecological approach,” said Yu, who is helping to coordinate the national project. According to The Guardian, these projects will include developing rooftop gardens, ponds, filtration pools, and wetlands, with permeable roads and public spaces designed to soak rainwater back into the ground.”
“It’s a new way of thinking about stormwater, not as a problem but as an opportunity and a resource to augment our water supply.” – Richard Luthy, professor of civil and environmental engineering at Stanford University.
One project that perfectly represents the Sponge City concept is Yanweizhou Park in Jinhua City. Completed by Turenscape Landscape Architecture in 2015, the project is a water resilient development with plantings designed to adapt to seasonal monsoon flooding. A resilient bridge and paths system permits both the flow of water currents and pedestrians, both adaptable as the season changes. The project utilizes the existing riparian sand quarries with minimum intervention to protect the local micro-terrain and natural vegetation. Rather than building high concrete flood walls up and around, the project incorporated floodable pedestrian paths and pavilions, both integrated with planting terraces designed to be closed to the public during periods of flooding. In addition to the terraced river embankment, the inland areas of the park are all permeable thanks to the use of gravel and re-used material across the pedestrian sections, with permeable paving used in the parking lot.
Is this “Sponge City” concept applicable to Los Angeles?
“Sponge City” seems a novel and catchy idea, yet the strategies and principles are actually an adaption of existing technologies already in play here, solutions inspired and sourced from the Low Impact Development (LID).
Actions have already been taken to make Los Angeles more “spongy”. An example: the Elmer Avenue Neighborhood Retrofit, a transformation of a residential street incorporating storm water best management practices (BMPs) to capture and filter runoff from a 40-acre area. Before the installation, the neighborhood was subjected to frequent flooding, but with vegetated bio swale and rain barrels, trench drain, and permeable pavers on the private driveway, the performance and appearance of the street is highly improved.
Moreover, increasingly more single-family homeowners are installing rain barrels to collect rain runoff from roofs to reuse for irrigations or cleaning. And for high-rise residential apartments, green roofs have been installed to reduce the runoff from roof.
While researching the concept of a Sponge City, I thought about the long-term benefits of these water-wise solutions in both China and here in Los Angeles. Even though we’ve already begun “pre-sponging” the city of Los Angeles by adding several green streets and green roofs, I believe we need to begin thinking of the infrastructure network as a whole system rather than individual sections. Site studies and research of both the Los Angeles Watershed and the city itself is required. However, I am optimistic about the idea of making Los Angeles a “Sponge City”, excited about scaling these water-optimization systems across all of Los Angeles.
I believe an important first step is simply spreading public awareness about the concepts behind a Sponge City. Currently, most Angelenos are not aware of these systems and solutions which could in sum alleviate the stresses placed upon Los Angeles by extreme weather fluctuations. Professor Anas Ghadouani, the regional executive director of the CRC for Water Sensitive Cities in Perth, Australia noted, “There is more awareness of the [drought] issue. When you compare it to somewhere like San Diego, I’d say Perth is well ahead; California seems to be shocked when there is a drought, whereas in Perth people are more aware of where water comes from. There’s a focus on diversity of sources that doesn’t surprise people now.”
It’s a notable point worthy of letting “soak in” as we plan for a more water-efficient future.
More resources about Sponge City:
- China bets on ‘sponge cities’ to cope with flooding and drought
- Why China Wants to Build Something Called ‘Sponge Cities’
- Perth’s water worries: how one of the driest cities is fighting climate change
- China’s sponge cities: soaking up water to reduce flood risks
- China Wants to Build ‘Sponge Cities’
- Building Sponge City: Redesigning LA For Long-Term Drought