Build Sponge Cities
From 2007 to the first half of 2013, more than 360 Chinese cities were hit by floods. Meanwhile, half of China’s 657 cities experienced water shortages, some to a severe extent, according to UN-Habitat data.
This paradox is attributable to the large extent of surfacing of urban land – in asphalt, cement, marble, and glazed tiles. Excessive development has thus destroyed forests, grasslands, lakes, and wetlands – the city “sponges” that store rainwater and regulate local climate. According to a Ministry of Housing and Urban-rural Development official, prior to urban development there was a 70-80 percent groundwater infiltration in northern China, so replenishing local bodies of water and feeding the ecosystem, while the remaining 20-30 percent drained. These percentages have now reversed.
Last year the Ministry of Housing and Urban-rural Development published a technological manual on building sponge cities. Construction of a low-impact system to collect rainwater prevents floods and forms a reservoir for the benefit of residents during times of drought. The ultimate aim is to restore resilience to urban land.