China's sponge cities alleviate urban flooding and water shortage: a review

About one tenth of humans are impacted by water shortages around the globe. Water resilience is worsening under climate change because intensifying weather extremes induce more severe and increasingly frequent droughts and floods. In particular, China, as the world's most populous nation, has battled with persisting water shortages and devastating floods for decades. As a consequence, Chinese scholars have designed the sponge city concept in the early 2010s to relieve cities from the growing pressure of water shortages and floods. This is done by integrating a more natural, green infrastructure into existing urban drainage pipeline systems for absorbing, storing, and purifying rainwater in a sponge-like manner during rainfall events. Here we review the principles, design guidelines, construction items and assessment requirements of sponge cities and other similar strategies for urban stormwater management. We present four case studies of sponge cities in China in both newly constructed and renovated urban districts. Overall, China's sponge cities appear promising for green urbanization, to relieve cities from water scarcity, devastating floods and urban heat island effects, while restoring the ecological functions and aesthetics of urban natural environments.