A sponge city is a new urban construction model for flood management, strengthening ecological infrastructure and drainage systems, proposed by Chinese researchers in early 2000 and accepted by the Chinese Communist Party (CCP) and the State Council as urbanism policy in 2014. It can alleviate urban flooding, water resources shortage, and the urban heat island effect and improve the ecological environment and biodiversity by absorbing and capturing rain water and utilizing it to reduce floods. Rain water harvested can be repurposed for irrigation and for home use. It is a form of a sustainable drainage system on an urban scale and beyond. Sponge city policies are a set of nature based solutions that use natural landscapes to catch, store and clean water; the concept has been inspired by ancient wisdom of adaptation to climate challenges, particularly in the monsoon world.
"Sponge cities are part of a worldwide movement that goes by various names: green infrastructure in Europe, low-impact development in the United States, water-sensitive urban design in Australia, natural infrastructure in Peru, nature-based solutions in Canada. In contrast to industrial management, in which people confine water with levees, channels, and asphalt and rush it off the land as quickly as possible, these newer approaches seek to restore water’s natural tendency to linger in places like wetlands and floodplains."
History
The People's Republic of China adopted the Sponge City initiative, largely motivated by the failure of the conventional grey infrastructure of flood control and stormwater management systems, due to the persistent efforts by Chinese ecological urbanists through letters and proposals sent to high level Chinese authorities since early 2000. Though the concept had been published and practiced since early 2000, it was the Beijing flood on July 21, 2012 which caused 79 deaths that prompted the top Chinese authorities to accept the Sponge City concept and make it a nationwide policy. In 2015, China was reported to have initiated a pilot initiative in 16 districts. This initiative presents an alternative to solve Asia's flood problems. China seeks to curb its flood with the initiative. The country plans for 80 percent of its urban cities to harvest and reuse 70 percent of rainwater. Building sponge cities does not necessary require huge investments. But such a fact has been widely misunderstood due to misleading media and the fact that the "sponge city" has been more than often misused by local government and contractors, as well as unprofessional designers as a fashionable brand and slogan which has actually nothing to do with this nature based solution. The major obstacles of implementing the nature-based sponge city are the business-as-usual mentality of grey infrastructure engineering, ornamental gardening and conventional urban planning, as well as the code systems that have been established to defend these obsolete urbanism practices. However, funding sponge cities has also been a challenge.
After achieving success in China, the sponge city model has attracted over-exposed climate zones such as Dhaka and Kenya, as well as major cities like Berlin and Los Angeles.
Background
Urbanization encourages the construction of city infrastructure. However, excessive utilization and development of water infrastructure can lead to water shortages, pollution, and overall degradation of water ecosystem services. Unscientific architectural planning also creates a large number of buildings, simultaneously limiting cities' green space, drainage, and rainwater collection ability. Consequently, rain discharge cannot meet modern cities' requirements, causing cities lots of problems regarding water ecology and aquatic environments.