With the combination of increasing weather extremes such as severe storms, the phenomenal growth of cities in many parts of the world, the potential for urban devastation is pronounced. With storms, increased rainfall often overwhelms rivers, drains and gutters, resulting in widespread flooding. However, some water managers are trying to view the abundance of this natural resource as an opportunity to rethink how the urban environment is designed and can function.
In China 54% of the population (750 million people) live in urban areas, covering 44.5×103 km2. This number is increasing at an unprecedented rate. Over the last decade in China, the pace of urbanization and industrialization, combined with the increased frequency of global extreme weather, has exacerbated urban water problems such as water scarcity, diminished water quality and flooding. Flooding is actually rated as one of the most destructive natural hazards in China with damage mostly experienced across cities, as a result of heavy summer rainfall.
One of the consequences of rapid urbanization in China was that underground infrastructure development, such as the drainage system, did not keep pace with infrastructure above ground. This means that during heavy downpours there is now not enough impervious surface area and retention capacity to allow infiltration and retention of storm-water. Additionally, many indigenous water systems such as city lakes and ponds, canals and peri-urban wetlands have not been maintained. As well as the loss of green and open spaces within cities, if the situation continues, Chinese cities will experience increased flooding, along with the associated social, economic and environmental cost.
In an effort to avoid this scenario, in 2013 the Chinese Central Government called for the widespread adoption of, ‘the sponge city' approach, providing the necessary financing for pilot activities across 16 urban districts for 2015 and 14 for 2016. Sponge cities are designed not only to channel rainwater away, but to actually reuse as much of it as possible, through enhanced infiltration, evapotranspiration and capturing methods, such as replacing concrete drains with permeable public spaces filled with native plants. In this way water can seep into the soil to replenish groundwater and be recycled for activities such as garden irrigation or sanitation. While the sponge city approach has gained momentum, with lessons already being learned and shared, there remain challenges to be overcome both within the pilot cities, as well as when rolling out the approach to the 600 plus cities in China.
Building with nature: Learning from the experience of the Netherlands
Given the lessons that it has learned in flood management and its successful integrated approach to building resilience with initiatives such as the ongoing Delta Plan, the Netherlands has long shared knowledge with other countries experiencing similar challenges. When asked by Chinese officials to help outline how the Netherlands could offer support to the specific challenges that China faces, the Netherlands Ministry of Infrastructure and the Environment, included UNESCO-IHE in the effort. Earlier this year, water experts of UNESCO-IHE conducted a number of field visits to several Chinese cities (Beijing, Nanjing and Zhenjiang) gathering information alongside representatives of national and local governments, scientists and practitioners working in the field of the sponge city approach, resulting in the production of a scoping report.
Later this month the Dutch delegation, led by Melanie Schultz van Haegen-Maas Geesteranus the Minister for Infrastructure and the Environment and including Prof. Arthur Mynett of Water Science and Engineering at UNESCO-IHE, will return to China. As well as conducting further fact finding on water quality, water reuse and flood management efforts, the mission will renew the Memorandum of Understanding between the two countries for continued collaboration over issues related to water and the environment.