·
The "sponge city" is an urban planning model designed to use "nature-based solutions" to distribute water better and improve drainage and storage. Sponge cities are a new approach to urban planning that emphasizes flood management and water conservation through the strategic use of green infrastructure. This concept is inspired by nature’s ability to absorb rainwater, mimicking a sponge. The term “sponge city” originated in China, it refers to “a new urban planning model in China that emphasizes flood management via strengthening green infrastructures instead of purely relying on drainage systems.”
The Concept of Sponge Cities:
The concept of sponge city has been introduced by Kongjian Yu, the Chinese landscape architect. The thinking is that one has to create structures that surround these rainwater systems and enable them to soak like a sponge. This approach is significantly different from the usual ‘grey infrastructure’ which uses pipes, drains and the concrete channels. However, sponge cities allow the natural water cycle procedures like natural retention basins, parks, wetlands, and green roofs, and permeable pavements.
Objectives of Sponge Cities:
Reduce urban flooding:
By increasing infiltration and storage of
rainwater, sponge cities aim to lessen the burden on traditional drainage
systems, thereby reducing the risk of flooding during heavy rainfall events.
Reduce
water scarcity:
Captured rainwater can be stored and reused
for non-potable purposes like irrigation or flushing toilets, reducing reliance
on strained freshwater resources.
Mitigate urban heat island effect:
Green infrastructure, like trees and parks,
can help to cool urban environments by providing shade and evapotranspiration
(the release of water vapor from plants).
Enhance ecological biodiversity:
By creating green spaces and restoring
natural waterways, sponge cities can provide habitat for various plant and
animal species, promoting a more diverse urban ecosystem.
Promote sustainable water management:
Sponge cities encourage a shift towards a
more natural and sustainable approach to managing water resources within urban
areas.
Importance of sponge cities in mitigating floods:
Rainwater Absorption and Retention:
Sponge cities are designed to absorb and retain rainwater,
reducing the volume of water that flows into drainage systems during heavy
rainfall.
Example: Rooftop gardens, permeable pavements, and open green spaces
are integrated into urban designs to allow rainwater to infiltrate into the
ground.
Natural Water Storage:
The concept involves creating natural storage areas, such as
wetlands and ponds, to hold excess rainwater and prevent it from overwhelming
drainage systems.
Example: The Tianjin
Eco-City in China incorporates wetlands that function as water storage
during heavy rains, reducing the risk of flooding.
Green Infrastructure:
Vegetation and green infrastructure, like bioswales and
urban forests, are critical components of sponge cities that help slow down and
absorb rainwater.
Example: Singapore's
Marina Barrage features a lush urban park that doubles as a water
catchment area, preventing downstream flooding.
Improved Drainage Systems:
Sponge cities often include enhanced drainage systems that
manage water flow more efficiently and prevent localized flooding.
Example: The Sponge City Initiative in Wuhan, China, involves
upgrading drainage networks and using sensors to monitor water levels in real
time.
Improved water table:
The use of permeable surfaces like permeable pavement and
porous concrete allows rainwater to seep into the ground rather than pooling on
surfaces.
Example: In Melbourne, Australia, the Water Sensitive Urban Design
approach includes permeable pavement in parking lots, reducing surface runoff.
Flood plain Management:
By creating and preserving natural floodplains, sponge cities
provide space for water to spread out, reducing the risk of inundation.
Example: The Thames
Barrier in London, UK, is a flood control structure that protects the city
by preventing storm surges from entering the river Thames.
Climate Resilience:
Sponge cities are designed to adapt to changing weather
patterns, making them more resilient against increased rainfall due to climate
change.
Example: Copenhagen,
Denmark, has adopted a sponge city approach to address rising sea levels
and heavy rainfall, incorporating green roofs and permeable surfaces.
