China's 'sponge cities' aim to re-use 70% of rainwater

by Asit K Biswas, Kris Hartley.

Updated 0907 GMT (1707 HKT) October 15, 2018

In 2012, a bridge leading to the town of Laishui, in northern China's Hebei province, just north of capital Beijing, collapsed. Floods in Beijing caused "significant losses."
Photos: Severe floods in major cities
Beijing, China (2012) – In 2012, a bridge leading to the town of Laishui, in northern China's Hebei province, just north of capital Beijing, collapsed. Floods in Beijing caused "significant losses."
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In 2016, following flooding in Wuhan, in China's central Hubei province, authorities issued an orange alert for heavy rain in central and southern parts of China. T alert is the second highest of China's four-tier warning system for rainstorms.
Photos: Severe floods in major cities
Wuhan, China (2016) – In 2016, following flooding in Wuhan, in China's central Hubei province, authorities issued an orange alert for heavy rain in central and southern parts of China. T alert is the second highest of China's four-tier warning system for rainstorms.
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During a period of heavy flooding in Nanjing, paramilitary policemen carried residents from their homes.
Photos: Severe floods in major cities
Nanjing, China (2016) – During a period of heavy flooding in Nanjing, paramilitary policemen carried residents from their homes.
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During the 2016 floods in Tianjin, an orange alert was issued -- during which time drivers navigated their vehicles through flooded roads.
Photos: Severe floods in major cities
Tianjin, China (2016) – During the 2016 floods in Tianjin, an orange alert was issued -- during which time drivers navigated their vehicles through flooded roads.
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Following the devastation of Hurricane Harvey in 2017, homes were surrounded by floodwater in Houston, Texas.
Photos: Severe floods in major cities
Houston, USA (2017) – Following the devastation of Hurricane Harvey in 2017, homes were surrounded by floodwater in Houston, Texas.
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Heavy rain showers brought Mumbai to a standstill. Pedestrians had to walk through flooded streets, while dozens of flights and local train services were canceled.
Photos: Severe floods in major cities
Mumbai, India (2017) – Heavy rain showers brought Mumbai to a standstill. Pedestrians had to walk through flooded streets, while dozens of flights and local train services were canceled.
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In 2017, floods in Nepal caused great damage to homes. A man is pictured resting in his house in Itahari, Sunsari district, some 250 kilometers from capital Kathmandu.
Photos: Severe floods in major cities
Itahari, Nepal (2017) – In 2017, floods in Nepal caused great damage to homes. A man is pictured resting in his house in Itahari, Sunsari district, some 250 kilometers from capital Kathmandu.
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In Cox's Bazar, Bangladesh, villagers stood near a broken embankment to avoid floodwater after the area was hit by torrential rains from Cyclone Komen.
Photos: Severe floods in major cities
Cox's Bazar, Bangladesh (2015) – In Cox's Bazar, Bangladesh, villagers stood near a broken embankment to avoid floodwater after the area was hit by torrential rains from Cyclone Komen.
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Story highlights

  • Chinese cities are struggling with flooding in urban, concrete areas
  • Sponge cities aim to capture and utilize this rainwater

Asit K. Biswas is a distinguished visiting professor at the Lee Kuan Yew School of Public Policy, National University of Singapore. Kris Hartley is a lecturer in city and regional planning at Cornell University.

(CNN)Asian cities are struggling to accommodate rapid urban migration, and development is encroaching on flood-prone areas.

Recent flooding in Mumbai was blamed in part on unregulated development of wetlands, while hastily built urban areas are being affected by flooding across India, Nepal, and Bangladesh.
    This is not a trend only in developing countries; floods in Houston, United States, highlighted the risks of development in environmentally sensitive and low-lying areas. In 2012, a severe flood in Beijing wreaked havoc on the city's transportation systems, and in 2016 floods overwhelmed drainage systems in Wuhan, Nanjing, and Tianjin.
      The challenges are clear.
      Read: A third of Bangladesh under water as flood devastation widens
      Read More
      Groundwater over-extraction, waterway degradation, and urban flooding are forcing China's cities to address a vicious cycle. Sprawling urban development and use of impervious material prevent soil from absorbing rainwater, prompting further investment in infrastructures that typically impede natural processes and worsen flood impacts.
      China's "sponge city initiative" aims to arrest this cycle through the use of permeable surfaces and green infrastructures.
      However, the initiative faces two challenges: lack of expertise of local governments to effectively coordinate and integrate such a complex set of activities, and financial constraints.

      The concept

      Engineering solutions are popular interventions, but cities cannot simply pipe away flood risks.
      To address the issue, China's sponge city initiative has an ambitious goal: by 2020, 80% of urban areas should absorb and re-use at least 70% of rainwater.