Sponge cities are the low-hanging fruit of flood mitigation 

Reuters

When I relocated with my family from Washington DC to Dubai in 2023, the last thing on our minds was that we might get flooded. 

Fast-forward a few months and all I think about is how something called a “sponge city” may help this emirate to alleviate the impact of heavy rainfall.

As the climate becomes more erratic, eschewing concrete-based drainage infrastructure in favour of nature-based landscaping to corral out-of-control stormwater is simply about the “art of survival”, Kongjian Yu, a Chinese landscape architect and a champion of sponge cities, tells me. 

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For the uninitiated prospective resident, as we were a summer ago, a cursory internet search will reveal that Dubai receives about only five days of rain per year, with combined precipitation of less than 200mm annually.

And yet, everyone here knows that’s not how things have turned out thus far in 2024. 

It is nearly a month since historic rainfalls submerged wide swaths of the city in mid-April, rendering several metro stations and tracts of roads unusable.

We were among the fortunate ones in that our house only had water seeping in through the windows, but many people lost everything in the flooding.

It goes without saying that the once-in-a-century April 16 storm, which dumped more rain in certain parts of the UAE in one day than the nation typically gets in a year, was a “black swan” event that local authorities were hard pressed to have predicted or prepared for with any accuracy.

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But with climate change expected to make these kinds of extreme weather events more frequent, the question of what this arid desert country can do to avoid a repeat of April 16 is increasingly an urgent one.

It is the question I have been asking many urban planners, engineers and architects from around the world ever since, and I’ve been surprised to get the exact same answer from all of them.

Dubai, and the UAE and Gulf countries in general, must transform their urban environments into “sponge cities” if they want to thrive. 

The concept originated in China, where it remains more widespread, and in its initial intentions targeted wetter, monsoon-driven climates.

But Yu tells me that it might just be especially suited to places like the UAE, where rainfall is infrequent but can come on violently all at once, as was the case last month.

“Climate change is monsoon-like,” he says. “Like the monsoon, you have very high precipitation in a very short period of time and it’s very dry during the rest of the year.”

In 2023, Yu won the prestigious Cornelia Hahn Oberlander International Landscape Architecture Prize awarded by The Cultural Landscape Foundation in Washington DC – a cousin of the better-known Pritzker Architecture Prize.

Concrete infrastructure traditionally used in drainage systems, particularly in Europe, quickly channels rainwater away from cities, typically into the sea, according to Yu and other industry experts.

But it is harder to tailor to environments with irregular rainfall, where it can become easily overwhelmed.

Green infrastructure including wetlands, playgrounds and even flower beds – as long as they are below street level – can instead act like a sponge, absorbing precipitation from above, slowing its flow and allowing it to seep into the ground down below into the natural and artificial stores within it.

“If you have 200mm, it is nothing,” says Yu. “For example, in Beijing in some areas we are talking about 300mm or even 400mm precipitation. 

“In my experience, if you have 20 percent of green space for stormwater and the design to carefully distribute it, you will solve the problem. But you need master-plan thinking to have a well-designed sponge system.”

Yu has recently visited the UAE as well as Saudi Arabia, where he is in talks for possible work at Neom’s The Line development. And he says the sponge city concept can both help to manage flash-flood-like events and ensure that aquifers such as the one underneath the ancient Saudi city of Al-Ula endure.

Combined with rain-harvesting efforts, the sponge city can also provide dry lands with some additional water for irrigation, toilet flushing and other non-drinking purposes, other experts have told me over the past month.

And it is a much cheaper solution, Yu notes, requiring about a quarter to a third of the costs of retrofitting a city with traditional drainage systems.

Not to mention the fact that it adds vegetation and hence shade to an urban environment, with the not-so-inconsequential result of beautifying, and perhaps even cooling a place like Dubai. What’s not to like?

Ultimately, smart, flood-resilient landscaping may not be the be all, end all answer to Dubai’s emerging stormwater management challenges. It is likely that a more wide-ranging approach that also includes traditional drainpipes and other such systems may ultimately be what is required. 

But it does sound like the low-hanging fruit of flood mitigation, and certainly worth a try.

Valentina Pasquali is AGBI’s construction and real estate editor