Creating sponge cities with nature-based solutions
On June 30th, IUCN together with WRI hosted a GrowGreen webinar to share experiences of Wuhan and Manchester in using nature-based solutions (Nbs) to create “sponge cities” and tackle water and climate-related challenges.
The sponge city concept refers to a type of urban management that allows cities to resolve urban waterlogging, improve water storage and discharge capacity, enhance water quality, and alleviate heat island effects through a mix of nature-based solutions and grey solutions. Sponge cities also prioritise the protection and restoration of original ecosystems in the urban area, such as rivers, lakes and wetlands.
The webinar was moderated by Chantal van Ham, from IUCN, who provided an introductory presentation of the objectives of the GrowGreen project. She introduced the webinar as an opportunity for exchange of knowledge, experiences and ideas between European and Chinese cities, drawing on the strengths of the various approaches to enhance the benefits of nature-based solutions for managing floods and other societal challenges.
Yunyue Peng, from GrowGreen, provided a presentation on using nature to reshape cities and live with water, and presented the Chinese Sponge Cities Programme, focusing on the experience of Wuhan.
She explained that China has been facing water management challenges and climate change has only exacerbated this problem. A number of funds at national level have been made available to promote the Sponge Cities Programme in Chinese cities, supporting the national target of reaching 20% and 80% of urban areas with sponge cities requirements by 2020 and 2030 respectively.
She reported that in Wuhan, also known as the city of 100 lakes, the 2020 target has been successfully achieved by introducing a mix of green and grey solutions. Despite the intense precipitation, the number of waterlogging points and their duration was significantly reduced in the two city’s demonstration areas.
Professor James Rothwell, from the University of Manchester, presented the Manchester Green Infrastructure Strategy and the West Gorton Park.
He explained that the strategy, adopted in 2015, included a number of objectives to be reached by 2025, related to the improvement of the quality and functioning of existing green and blue infrastructure, ensuring effective education and understanding to promote citizen engagement and integrating green and blue infrastructure in new developments. Several activities have been put in place to achieve such objectives, including enhancement of wetlands and forests, engagement of developers with green infrastructure schemes, and tree planting.
Through the GrowGreen project and building on the experience of Wuhan, Manchester established a new park that “drinks water” in West Gorton. The park embeds Nbs and sponge city principles to address water-related challenges (e.g. rain gardens redirecting runoff). He highlighted the importance of the engagement of the local community in designing the park and every stage of the implementation, creating a sense of ownership and bringing people together.
Helen Ding, from the World Resources Institute, introduced a global study looking at adaptation actions around the world which showed that every $1 invested in climate resilient infrastructure can generate a return of $5.
She also introduced a WRI project in China, focused on three types of climate risks in three Chinese cities: Ningxia, Wuhan and Shenzhen. The study, which will be published in September, assesses the avoided economic damages and the social, economic and environmental benefits resulting from investing in Nbs.
In the case of Wuhan, the avoided damages referred to direct asset damage, operation cost of urban pipeline network and cost of water pollution control. The related economic benefits included stormwater recycling and added real estate value. A number of environmental and social benefits were also assessed, including increased groundwater recharge, reduced air pollution and increased recreational value.
She concluded that the study demonstrated that the economic return on Wuhan Sponge City construction was of $2.3 for every $1 invested in climate-resilient infrastructure. Further details will be disclosed with the publication of the study.
Dr. Jinqiang Chen, Stefan Rau and Hinako Maruyama, from the Asian Development Bank (ADB), presented the key considerations for mobilizing finances for Nbs.
Dr. Jinqiang Chen explained that a national policy exists in China to support the development of sponge cities and that all cities have formulated their own sponge city plan by 2016. He introduced the Climate Resilient and Smart Urban Water Infrastructure project. The project, with a loan of $200 million (to a private sector company), includes a number of techniques for climate resilience as technical requirements in the loan agreement to reduce the severity of flooding.