Sponge Cities: China's Answer to Overwhelming Urban Flooding

Cities across the globe are learning that they have to pay more attention to the natural world around them. Whether that's because of flooding, wildfires, droughts, landslides, or storms, they have to make some big changes. In 2015, after fatal floods had become a regular occurrence, China decided to get serious about reducing the flood risk in their cities and embarked on a project to create 'Sponge Cities.'

The goal of these sponge cities is exactly what you may think - to act as a sponge and reduce the amount of water on the surface that could trigger a flood. The project launched in 2015 with sixteen sponge cities, and an additional fourteen cities were named in 2017 to bring the total up to thirty. The initiative's ambitious goal is that by 2020, 80% of urban areas should absorb and re-use at least 70% of rainwater.

The largest sponge city yet is Lingang, a city within Shanghai's Pudong district. The city government of Lingang has invested $119 million in the sponge city project and is hoping to become a model for modern urban water infrastructure. The streets of Lingang have been paved with permeable pavements, allowing rainwater to filter through the pavement to the dirt below. This is a pretty big deal in China, as their rapid development has frequently used concrete and created huge swaths of impervious surfaces in cities. In fact, the China water management team at Arcadis estimates that currently only 20-30% of rainwater currently infiltrates the ground in urban areas.

Lingang is implementing a variety of measures to reduce flooding including planting gardens on their rooftops, creating scenic wetlands in the city for rainwater storage, and switching to permeable pavement. To date, China has spent over $12 billion on their sponge cities, with the central government directly funding 15-20% of the costs. The rest of the bill falls to local governments and the private sector. Unfortunately, the renewed push for sponge cities falls during a municipal debt crisis in the region and investment has stalled.

China is taking action with these sponge cities not just to prevent flooding, but also to prevent landslides. Landslides and flooding killed

China's sponge cities are just one example of an increase in sustainability planning happening in cities across the globe.

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