Engineers measure up Dubai’s $8bn flood defence plan

• Massive drainage system upgrade
• Likely to use ‘traditional’ approach
• Experts point to cheaper green options

After April’s once-in-a-century storm that put swaths of Dubai under water, Sheikh Mohammed bin Rashid Al Maktoum has cleared the way for a AED30 billion ($8 billion) stormwater management upgrade.

The ambitious expansion of the emirate’s drainage system will provide a sevenfold increase in its capacity to handle rainwater, to more than 20 million cubic metres of water a day – the equivalent of emptying 5½ Olympic-sized swimming pools every minute.

But as the Dubai authorities start work, industry specialists have said they should not eschew smaller and cheaper solutions that may go a long way to mitigate the impact of heavy rainfall and flooding.

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Work on the flood defences project, named Tasreef, will begin immediately and take nine years to complete, according to the emirate’s ruler. Sheikh Mohammed also said the construction crews would use the Middle East’s newest and largest tunnel-boring machines.

The announcement was scant on details, but the project’s scale and price tag suggest authorities are looking at a traditional approach to increase drainage pipe capacity, experts told AGBI.

“We can expect a mix of traditional below-ground infrastructure which entails pipe networks, tunnels, pump stations and sea outfalls, as well as surface infrastructure such as channels, culverts, ponds and other green infrastructure,” said Nariba Gittens, associate director, water, for the Middle East at WSP, a Canadian consultancy. 

Sheikh Mohammed said the project would build on drainage upgrades initiated in Expo Dubai, Al Maktoum International Airport City and Jebel Ali in 2019.

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“There will undoubtedly still be surface excavations, but much of the work will be undertaken with less inconvenience to the general public,” Gittens said.

“The most challenging will be the retrofit required in already built-up areas of Dubai, where the availability of space above and below ground is limited.”

It is not yet clear how the newly announced spending fits with the funds already allocated to shoring up the emirate’s water management system through ad hoc deep sewerage tunnels in north and south Dubai, and the 2040 urban masterplan.

Hazem Gouda, an associate engineering professor at the University of Wollongong in Dubai, said contractors stand to receive nearly all the money for the construction work. Only 5 to 7 percent of the budget is expected to go to engineering and design consultancies, and, ideally, maybe around 4 percent to the developers of smart AI-based systems that can combine the management of surface water, roads and traffic, Gouda said. 

Alamy/Arnold Pinto

“There could be potential to change the building codes to use building roofs as a rainwater storage during rainfall events,” Gouda said.

“It’s crucial to integrate the city’s masterplan, considering the use of roundabouts and tunnels during extreme events, recharging groundwater aquifers, and exploring the potential of coastal reservoirs for future needs.”

Dubai could look to Singapore’s revamp of its stormwater management infrastructure under the Active, Beautiful and Clean Waters programme, and New York’s work on flood resilience after Hurricane Sandy in 2012 as examples of the way forward, sources said.

There are solutions that are not costly and might not solve the problem completely, but they can at least help

Peiman Kianmehr, American University in Dubai

Tokyo’s “enormously expensive” tunnelling system, on the other hand, might serve as a warning, according to Ronny Berndtsson, professor of water resources engineering and deputy director of the Centre for Advanced Middle Eastern Studies at Lund University in Sweden. 

In the 2000s, Japan’s capital spent heavily on a hard-infrastructure anti-flood system that is among the largest in the world. But even that may not be enough for the increased frequency of extreme weather events, Berndtsson said. 

Experts suggested the authorities in Dubai should not forget to be creative in devising a response to erratic rainfall.

Green solutions that harness the natural environment and landscaping should be a priority, they all said.

Peiman Kianmehr, chair of the Department of Civil Engineering at the American University in Dubai, said: “There are solutions that are not costly and might not solve the problem completely, but they can at least help.”

He suggested that the emirate should consider incorporating in all developments permeable surfaces that allow rainfall to seep through.

It should also require developers, and individual villa owners, to reserve certain portions of their lots to serve as temporary flood zones in the event of a catastrophic storm, Kianmehr said.