Sponge City



In 2013 China’s president Xi Jiping decided that all the cities in his country had to become some sort of sponges. Resilient urban landscapes, permeable to torrential rain, able to absorb water during the showery seasons and give it back, clean, during drought months. That’s how China kickstarted a program involving substantial public and private investments aimed at finding solutions to the catastrophic consequences of climate changes, which involve months of either severe drought or violent and devastating rain. According to the data gathered by some observation centres working for insurance companies, the natural disaster that causes the most damages – on a human, social and economic level – is flooding. And in the past 20 years, flooding has affected over 2.3billion people in the world.

Anti-flood plans in China now expect urban areas to develop natural systems for rain drainage, retention and purification. Which means that more than 30 cities, populated by over 450m residents, are expected to devise new solutions inspired by sustainability principles and by some water-sensitive urban design projects carried out in Australia and Europe. The need to create environments resilient to extreme climate changes is not exclusive to China. Even European capitals such as London and Berlin have implemented urban regeneration programs aimed at coping with heat waves and torrential rain, by laying over roof surfaces both musk and other plants able to absorb rain and return it in the form of water vapour when the temperature rises, cooling the surrounding areas down. Or by devising a system of gardens, ponds and lakes where excess water can flow into, preventing drainage basins and rivers from overflowing under the pressure of violent and incessant rain.

The idea has been explained in detail on Bloomberg News by Carlo Becker, the Berlin-based architect set on turning the German metropolis into a Sponge City. Normally in cities rain gathers into drainage pipes, which pour it elsewhere. This practice, however, causes urban centres to overheat in summer and be more susceptible to flooding. Carlo Becker reckons that large cities must go back to basics and start mimicking nature again. How? By finding a way of absorbing rain.

The first sponge-neighbourhood in Berlin has just turned 20 years old. No manholes and no rain drainage pipes: water gets completely absorbed by the sponge gardens surrounding buildings and roads. Beijing will see its first pilot project completed within 2018 and according to the Guardian newspaper, will also allocate around £46million pounds to those urban agglomerates that have expressed an interest in becoming part of the national project of flood prevention and control. We shouldn’t contrast the course of nature, we should imitate it.