ASFPM Shares LID & GI Knowledge, While Soaking in Chinese Sponge City Sites

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.