Lisbon has invested €250 million in a major drainage plan that combines large-scale infrastructure with green solutions to reduce flood risks and position the city as a European leader in climate resilience.
This is neither a new metro line nor one of Elon Musk’s ventures. The new five-kilometre tunnel connecting Lisbon’s northern districts to the Tagus River is designed to shield the capital from the torrential rains expected to hit Lisbon in the coming decades.
“This is unique — there’s nothing like it in Europe,” says Lisbon Mayor Carlos Moedas, a former hydraulic engineer and ex-European Commissioner for Innovation, who pushed forward a project debated for decades.
“Politicians usually prefer visible projects. I had to convince residents that we were building something invisible, but very, very important for them,” Moedas told Euronews.
On 22 July, after three years of construction, Moedas and EU Commissioner for the Environment Jessika Roswall celebrated the arrival of the tunnel boring machine at Santa Apolónia, a spot on the River Tagus that welcomes thousands of cruise passengers each summer.
Adapting to climate change
According to researchers at the University of Lisbon, episodes of extreme rainfall (up to 120 mm in 24 hours) could become five times more frequent in the coming decades.
In the event of a storm, several entry points along the five-kilometre tunnel will be able to capture up to 175 cubic metres of water per second, diverting it directly into the river.
A second, one-kilometre tunnel will soon connect the Chelas and Beato neighbourhoods. The mayor argues these projects are cost-effective:
“Two years ago, within a single week, Lisbon was hit by two so-called ‘100-year’ rains. People lost their homes and their businesses. It had a huge impact on the city,” Moedas recalls.
The system also includes retention basins and pollution control measures to treat stormwater. Part of this water can later be reused to irrigate parks or clean the streets.
“When I explain to residents that reusing rainwater will save us millions of euros previously from water bills, they say ‘oh, the mayor is doing the right thing,’” adds Moedas.
Nature-based solutions
Beyond the tunnels, the plan also relies on nature-based solutions, including infiltration basins and permeable soils in several parks and gardens across the capital.
This ’sponge city‘ strategy — capturing, storing and reusing rainwater — is the very model put forward by the European Commission, which unveiled its new resilience strategy this summer.
Still, financing such infrastructure remains a major challenge for many towns, especially small and medium-sized municipalities.
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