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ASFPM Shares LID & GI Knowledge, While Soaking in Chinese Sponge City Sites
Wednesday, October 24, 2018

Written by Bill Brown, P.E., ASFPM's Flood Science Center Director

ASFPM received an invitation from the China Urban Infrastructure Chamber of Commerce to participate in the 2018 Third China Sponge City International Exchange Conference Sept. 27-29, 2018 in Nanjing, China. The conference was an opportunity to convey experiences, information on new technologies and products related to China’s "sponge cities" initiative. The effort aims to arrest the impacts of groundwater over-extraction, waterway degradation and urban flooding through the use of permeable surfaces and green infrastructures. The goal is to design urban landscapes as active systems that soak up excess rain to improve waterway health and mitigate flooding. Through permeable green infrastructure replacing impervious grey engineering, a sponge city retains stormwater for reuse within its own boundaries. The retained stormwater can be used to sustainably recharge depleted aquifers, offset potable water demand, supply industry and for urban irrigation.

The sponge city initiative is similar to low-impact development (LID) or green infrastructure (GI) efforts in the United States. While much of the efforts in China are focused on new urbanization, there is also a focus on retrofits to existing urban areas. The Chinese government has called for existing urban areas to incorporate water management best practices in redesign and retrofitting projects.

During my participation at the conference, four Americans were speakers and invited to meetings with various Chinese representatives. In one meeting, we met with Ms. He Junjun, deputy director, Urban Construction Department, Housing and Construction Department, Jiangsu Province and her staff to discuss our experiences with LID/GI. The meeting was very informative and engaging. The questions asked by the Jiangsu Province staff were consistent with issues faced by county and municipal governments throughout the United States—project funding, design standards, design challenges, construction and maintenance.

As part of ASFPM's invite, we were asked to present to the conference attendees. Giving the focus on LID/GI and its impact on flood-risk reduction, my presentation focused on infrastructure projects in urban floodplains. My presentation, "Greening a Grey System: Green Infrastructure Designs in Urban Systems" promoted the "greening" of existing infrastructure retrofits or redesigns, as well as the natural and beneficial functions of floodplains. As is an issue in China, many older communities in the U.S. experienced rapid urbanization with little regard to flood risk from the stormwater systems. I highlighted how various projects were traditional grey 

designs, but incorporated green aspects, bioengineered streambank stabilization and floodplain buyouts where the land was turned into and maintained as open space. There was great interest in successes and experience in the United States and other countries.

On the final day of the conference, we visited two sponge city project sites in Nanjing. The first was a floodplain restoration site adjacent to a road that repeatedly flooded. A vacant adjacent lot was remediated to expand the floodplain storage and was turned into a park amenity that included educational signage to explain floodplain benefits. The project utilized pervious pavement for the trails and parking areas, native vegetation and expanded floodplain storage. The second site was similar to a Complete Streets design in the United States where there was dedicated pavement for cars, a vegetated median separating the street from a bike lane and then the curb and sidewalk draining to a bioswale. The designs were very similar to projects you might see in the U.S.

Overall this was a very memorable on a personal and professional basis. There are many opportunities to share successes in flood and stormwater management. There was interest by many in China in further developing these opportunities.

Photo by Bill Brown. A Nanjing, China sponge city site. This floodplain restoration project is adjacent to a road that repeatedly flooded.






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