Gazillions of tones of pristine water tumble from the sky, and yet water is not free. The vast majority is channeled down into sewers, ditches, and finally into waterways. 

At the very least, this is a misuse of precious earth’s resources and our lifeline! What’s worse, while some of us struggle to get a clean glass of water, the rest of the world is devastated by excessive water. 

In the worst-case scenario, it might result in deadly city flooding like those that hit the Japanese city in Joso, killing eight people and destroying dozens of livelihoods. 

Anthropogenic climate change and a growing global demographic both provide significant issues in two segments that are intertwined: an upsurge of catastrophic flooding in many locations and a scarcity of pure and safe drinking water in the same areas.

There is no room for the rainwater to run through as heavy downpour progresses in metro communities, especially low-lying ones, which are vulnerable to flood disasters. 

Concrete pavement and other hardscape surfaces allow the precipitation to stagnate and overflow. Flooding defenses and stormwater run-off may be adequate for a regular downpour. 

Still, they may be overrun by increasingly powerful storms, notably when rising water levels in nearby waters are critical complicating phenomena. 

Furthermore, city floods can exacerbate health concerns by mixing wastewater with rising waters, resulting in substantial social and fiscal losses.

In the past few years, numerous locations in Thailand have experienced severe flooding. Bangkok’s 2011 flooding is associated with an approximately USD 46.5 billion loss. One of the largest cities in Isan’s northeast, Udon Thani had also been severely affected. 

The town’s wastewater infrastructure was nearly always overloaded during the rainy season. Vast swaths of land were waterlogged, residences and perhaps other structures were submerged, and roadways inaccessible. 

Urban planners, architects, and researchers have collaborated for a very long time to explore the viability of using natural systems to absorb surplus water. 

Today, they have finally created a natural connectivity platform that connects green areas around the city by combining meteorological parameters with architectural and prototyping techniques. 

Marshes and eco-friendly areas “cushion” flooding and minimize water disasters by restraining stormwater run-off and enhancing penetration. They essentially behave like a sponge, soaking up water just before a storm surge.

China pioneered the planet’s first sponge cityscapes. The concept is already being incorporated in urban building blueprints in some of the globe’s most flood-prone regions, including the German state of North Rhine-Westphalia, which is devastated by floodwaters every other summer. 

After catastrophic flooding in Beijing in 2012, the Chinese government implemented a sponge city urban development program that has since stretched to over 30 cities across China, including Shanghai and Beijing.

Thirty pilot cities in China are currently attempting to collect and retain more rainwater in order to address issues ranging from flood and drought to grilling heat and pollutants. 

Rather than diverting rainfall downstream via sewer lines and trenches, these pilot cities must develop strategies to capture, collect, cleanse, refine, keep the waters within their bounds, and discharge as and when desired.

Table of Contents

What is a sponge city?

An archetype sponge city
An archetype sponge city | Image Credit – Chuttersnap

A sponge city is premised on a revolutionary mindset that an advanced civilization can tackle water issues rather than create more. 

In the big scheme of things, sponge cities will aid in combating climate change by reducing greenhouse gas emissions. Hit two birds with one stone!

Rainwater management is a critical component of long-term city planning and economic renewal. 

Ponding and flooding, metropolitan water shortages, surface run-off, rainstorm squandering, and water contamination are all consequences of poor storm administration in communities. 

In numerous nations, such as China, India, Pakistan, and Iran, minimal or zero prohibitions on sewage and drainage layout and poor urban design approaches have resulted in extreme floods. Adopting the ‘Sponge City’ technique is a beneficial means of minimizing such harm.

It is basically an urban region that uses several ways to deal with excessive rains. Contemporary metropolitan areas frequently experience floods due to massive rain, tidal waves, or overflowing waterways. 

And, sponge city architecture can help lessen or eliminate such catastrophes by allowing the land to soak the moisture spontaneously.

Essentially minimizing the fraction of concrete surfaces and promoting the quantity of water-absorbing acreage, especially green space, can help to reduce the intensity and likelihood of drowning episodes. 

On the other hand, water scarcity, which can be especially problematic in major cities, can be mitigated by complementing this strategy with appropriate channeling and storage solutions.

A sponge city is intended to produce a far more porous urban landscape so that rainwater from such catastrophes may be more successfully sucked-up and stored in underground reservoirs for subsequent purification and usage. Contaminated run-off concerns are also reduced or eliminated with a smart sponge city concept.

What does a Sponge City need in practice? 

Sponge City
Much Needed sponge city | Image Credit – Nancy Bourque

Water must be able to infiltrate into sponge cities; thus, there must be plenty of openings for it to do so. The metropolis requires more than impervious paved surfaces and cemented blocks. 

It necessitates green zones, interconnecting streams, networks, and reservoirs that may dynamically hold and purify water while fostering urban habitats, increasing ecology, and providing social and outgoing possibilities among neighborhoods. This reason is what keeps the sustainability factor in check.

Green roofs collect rainfall and cleanse it biologically prior to recycling or releasing it into the earth. 

Development of bio-swales and bioretention mechanisms to capture run-off and permit underground infiltration, highly permeable road systems and sidewalks that permeate and replenish aquifers, and sewage platform that enables rain to trickle into the surface or immediate downpours run-off into green areas for regular intake are all examples of highly permeable innovative concepts throughout the sponge city. 

The mechanism of a Sponge City

Some widespread flood water management techniques are installing pipelines or channels to draw water away as quickly as possible or fortifying embankments with manufactured structures to keep them from overflowing. 

On the other hand, a sponge city seeks to absorb precipitation and minimize surface run-off extensively. It strives to accomplish this in three simple mechanisms.  

The first would be at the origin, where a city attempts to collect rain with multiple pools, much like a sponge with several pockets. 

The second is via circulation, where, rather than trying to direct water away rapidly in a parallel plane, a sponge city diverts water towards plants or wetlands and delays the flow. 

These cities have the potential to generate significant advantages to green zones, gardens, and wildlife and purify downpour run-off by eliminating harmful pollutants and minerals through the application of plants. 

The third mechanism is the draining process that dumps the water into a stream, reservoir, or ocean. 

Professor Yu calls for the land to be relinquished and structural development to be avoided in low-lying regions. Sponge cities are becoming progressively ingenious, inefficiently warding off dangerous flooding and climatic extremes, from enhanced drainage channels to water-absorbing streets and innovative vegetation.

Implication towards climate and ecosystem

Flood management, sediment administration, and water treatment are all potential advantages of sponge city developments that rehabilitate our ecosystems and duplicate the natural flow of water, both of which can assist water treatment and reduce climate catastrophes.

Decking residences and skyscrapers with green rooftops and canopies and developing urban marshes and excavations to screen rainwater to recharge reservoirs, nourish plants and urban farmland, flush toilets are all strategies implemented in sponge cities. Other environmentally sustainable features include:

  • Building breathable pavements that allow moisture to seep into the earth.
  • Make roads and gardens more absorbent, and completely concrete surfaces should be redesigned.
  • Absorb and retain precipitation efficiently with the introduction of wetlands.
  • Building rooftop gardens and green spaces.
  • The government should plant trees along roadways, public recreational areas, and community playgrounds.
  • Increase the number and expanses of green space, community gardens, and parks.

Tacking the heat

As urban areas in China and around the globe as a whole become warmer, sponge cities have yet another advantage that appears destined to serve as a huge asset. 

They can mitigate the effects of rising temperatures and heatwaves, which are more apparent in urban areas because of the heat-trapping properties of cement and concrete structures. 

Water is absorbed by trees and shrubs, subsequently released through perspiration. This procedure has a cooling effect, similar to how moisture evaporates from the skin’s epidermal surface and keeps us cool.

Reduction of drought 

Another undeniable benefit of a sponge city is increased access to water supplies for urban metropolises due to recharged aquifers. 

Higher moisture self-sufficiency is also sought, allowing cities to remain dependent on water resources within their frontiers—increased volume of sustainably processed stormwater results in safer subsurface water. 

As a consequence of the notable reduction in water contamination, there will be decreased health, environmental and economical expenses. 

Hence, sponge cities are being constructed as new eco-cities to deliver a technique for incorporating the water cycle into city development.

To Wrap Up

Sponge city are a temporary solution to a far fetched tragedy
Sponge city are a temporary solution to a far fetched tragedy | Image Credit – GEORGE DESIPRIS

Thus, according to the architectural firm Turenscape, as we approach 2030, at least 70% of Chinese towns are hurrying to write up a proposal per need and interest as the sponge city concept expands. 

This novel invention has demonstrated that sustainable architecture may be more than just rooftop gardens and constructed wetlands; it can be a radical rethinking of a metro’s basic structure.

Sponge Cities are based on old agricultural and river management understanding, which employ basic instruments to modify the planetary landscape on a large scale in a long-lasting and multi-functional fashion. 

The future’s way of dealing with things! They are considered environmentally and economically sound and targeted to improve social amenities, primarily as climate change exacerbates catastrophes.  

Even as we speak, numerous communities throughout the globe are struggling to come to terms with heavier rains, a phenomenon related to climate change. 

More water evaporates into the sky when the climate warms due to global warming, resulting in more extraordinary rain. 

And it is just going to get more acute by the day. Undoubtedly, future precipitation will be more powerful and destructive than previously predicted.

However, is the sponge city the silver bullet for combating climate extremes in the face of stronger storms? 

Yes, they might be a temporary solution to a far-fetched tragedy. However, it is essential to realize that sponge cities alone will not hold up these climate extremities and spare life on earth for too long.

Humanity cannot fight the water. Hence, we might as well give in to it. 

(Last Updated on March 28, 2022 by Sadrish Dabadi)

Shradha Bhatta holds a Bachelors’s Degree in Social Work along with a Post-graduate degree in Project Management from Georgian College in Canada. Shradha enjoys writing on a variety of topics and takes pleasure in discovering new ideas. She likes traveling and spending time with nature. She is a very people-person who loves talking about climate change and alerting people to go green!