City under construction. But it won't stop the floods

In a single day, Lisbon had as much rain as it usually does, on average, throughout the whole month of December. On December 13, 2022, the Portuguese capital faced more than 110 millimetres of rain falling per square metre, with this day being (for now) the rainiest in history for this particular month. And just one week after the runner-up, the 7th of December, saw its own heavy rains hitting the city.

Enough rain, both times, to plunge Lisbon into chaos. The floods, significantly worse in the riverside areas, were seen all over the city – semi-submerged cars, flooded commercial establishments, blocked roads, flooded tunnels, people displaced and streets looking like rivers. A loss amounting to 49 million euros, with mayor Carlos Moedas asking for “maximum help” from the Government.

34 million euros, of the total amount, representing damages to infrastructure and public equipment, while 15 million, a 30% slice of all the damage, relates to damage caused to economic activities, commerce and services, and private homes.

The heavy rain – expected once every 100 years – didn’t just hit the city of Lisbon. Loures’ City Hall reported losses of 32 million euros; Oeiras is close to 19 million (and counting); Amadora is set on two million. Insurance companies took a toll as well. In a provisional balance sheet, the Portuguese Association of Insurers is forecasting, for the first week of this year, over 47 million euros paid.

“It’s amazing how something that hardly ever brings water suddenly becomes this monster.” The quote is from João Antunes, president of the Algés Parishes Union, Linda-a-Velha e Cruz Quebrada/Dafundo (independent, centre-right), who spent the early hours of December 13 near the Algés stream on a self-imposed watch. “It's a ticking time bomb, but we have to learn to live with it.” Dawn saw that lower area partially submerged. It’s not an unseen scenario, but one usually spaced out in time. “The last flood like this was 40 years ago”, explains João Antunes. 

In Algés, an area prone to flooding, there are two reasons for concern – the stream, coming from Amadora and Monsanto and conducted in an underground conduit to the Tagus, and the water that comes from Lisbon, drained by the slope of Avenida Dom Vasco da Gama.

“The Algés stream had not yet overflowed, and the area was already full of water”, he summarises. In 2008, a project was born to duplicate the underground stream course, through the construction of a second tube that would dilute the torrent on heavy rain days. 

Austerity policies saw this plan suspended. “It's time to take it out of the drawer. The floods will never end, that much is clear, there is too much water, but at least to minimise the situation.”

According to the current Algés Parishes Union president, the project was initially budgeted at 20 million euros, with the municipality guaranteeing half of the funding. “Now, it’s at 50 million and he [Oeiras’ mayor] continues to vouch for 50% of construction.” As Time Out was able to ascertain, the project was once again debated between the Oeiras City Hall, the Portuguese Environment Agency and the Commission for Regional Development and Coordination of Lisbon and Tagus Valley.

Alcântara saw the situation repeating itself. Once again, there were two aggravating factors in its physiographic vulnerability: the high tide and the underground aquifer with its source in Amadora – a channel also known as Caneiro de Alcântara – and flowing into the Tagus. “It rained at the height of a high tide. The water that came from the channel reached down there, found a wall of water and came back. And as it’s connected to the drains and gutters, that’s where it comes out. That’s why it flooded”, explains José Silva Ferreira, Lisbon Drainage Master Plan’s coordinator, whose main goal is to cease the flooding in this riverside area.

For António Carmona Rodrigues, former Lisbon mayor (PSD, centre-right), who graduated in civil engineering with a post-grad in Fluvial Hydraulic, the problem “is not the channel, nor the area”. “When the tide is high and there are large rain flows inside the channel, Alcântara’s lateral areas cannot drain into it. Only with lifting stations, with pumps to drive the water inside”, he says.

Without those pumps, the parish's urban evolution has witnessed some large-scale works. One of the most recent is the CUF Tejo Hospital, inaugurated in September 2020, which was soon in the news after the December floods. These types of structures hinder the rainwater flow and act as barriers instead, aggravating the situation for an area already prone to flooding. When reached by Time Out, the Alcântara Parish Council president failed to give any statements due to a lack of schedule. 

In José Luís Zêzere’s opinion, the director of Lisbon’s University Centre for Geographical Studies, the hospital build “should never have happened”. “Can I build on a floodplain? Sure. I’ll create a landfill and build it on top. This means that the usual flood zone has changed its setting, it’s now smaller. If it’s smaller, it will either flow into places it didn’t before or rise the flood level on those it already did. Or both. Assuming CUF has no damage at this point, the fact that it was built where it was has increased the damage level for those around it”, he maintains. 

The construction is shrouded in controversy. In February last year, an investigation by the Public Prosecution Service in Portugal into the hospital’s impact on the landscape had six defendants already, including Manuel Salgado, former city councillor for Urbanism and Urban Rehabilitation, architect Frederico Valssasina and CUF administrator, Guilherme Magalhães.

In Zêzere’s opinion, concern over urban planning should extend to the entire city riverside and account not just for floods, but for other imminent hazards as well. “There’s a bit of that idea of the nouveau-riche mentality that wants to build some houses with a balcony facing the sea [...]. We aren’t going to remove Praça do Comércio, nor Jerónimos. Now, I find it a bit harder to understand cases like Champalimaud, maat, the National Coach Museum or CUF Hospital. It’s like they’re pretending it has nothing to do with them. I’m sure those making these decisions aren’t crazy, but between the location’s symbolical trait - it’s one thing to have maat there, and something entirely different taking it to Odivelas - and the risk of an earthquake or a flood [...] the symbolism seems to matter more, meaning the risk awareness if not sufficiently ingrained.” Currently, efforts are focused on solving the problem upstream.

The desire to draw up a plan that would minimise the effects of cyclical floods came to be in 2002 when Pedro Santana Lopes (PSD) was the president of the municipality. Four years later, Carmona Rodrigues announced the preparation of a drainage plan for Lisbon. “The best that national engineering could do was in it”, says Carmona Rodrigues, who claims to have approved the plan in 2007. However, the work in progress today has the seal of António Costa’s presidency (PS, centre-left). Completed in 2008, seven years would come to pass before it was formally presented - an invisible construction with an execution timeline ranging from 2016 to 2030.

In 2023, it enters its most critical stage, the construction of two collecting tunnels - the biggest going from Campolide to Santa Apolónia, with rainwater collection happening on Avenida da Liberdade, Rua de Santa Marta and Avenida Almirante Reis, in addition to capturing part of the water from the Caneiro de Alcântara. In total, this underground structure will extend for 4.6 kilometres. The second tunnel, 1.6 kilometres long, will drain rainwater between Chelas and Beato. The tunnels, both 5.5 meters in diameter, are budgeted at 133 million euros, out of a total of 250 million, which is how much the drainage plan will cost.

“Basically, they will carry out the so-called interbasin transfer so that, when there is too much water in certain places, due to rainfall events, this water gets transferred to the tunnel, that will, in turn, take it directly to the river”, explains José Silva Ferreira, plan coordinator since 2014. But there’s more to it - a settling basin at the start of the great tunnel and a second one already planned, to be built later on, for the Chelas tunnel. According to the same person in charge, the interception of the Caneiro de Alcântara will be a key point in mitigating the effects of the floods a little further downstream. “This is where we will collect the water coming from the channel and likely to flood the whole Alcântara area, and we do an interbasin transfer. That is, all the water that is too much for ETAR to treat is removed towards the tunnel.” There’s no doubt in his mind about the outcome: “There won’t be any floods in this area once the tunnel is built. The channel will be freer, it won’t drive so much water towards Alcântara and the current situation will cease to happen again.” 

The downward path of the larger tunnel will create a vortex that will lead the water to the river, without any connection to the sewage system nor the gutters. “What leads to the flooding in Baixa? The waters coming from Avenida da Liberdade, Rua de Santa Marta/São José/Portas de Santo Antão, and Avenida Almirante Reis, valley areas that used to have streams in the past. From there to downstream, the entire network that exists will get freer and there won’t certainly be floods caused by waters coming upstream." 

This construction will have an impact on everyday life in Lisbon. Santa Apolónia and Avenida da Liberdade are likely to be the most affected areas. The engineer foresees “some confusion” on the first, and a “limitation” of traffic and people movement for the latter, where some night work might only leave a single lane clear. “We hope that, between March and April, construction on the biggest tunnel will begin. All going according to plan, we should reach Santa Apolónia within a year.” Construction is expected to be complete between mid-2024 and early 2025. The smaller tunnel - with construction going from Beato towards Chelas - will only start after the first one’s complete and should be done in four months' time. 

The Drainage Master Plan already has some completed works throughout the city – the large retention basins in the Ameixoeira and Ajuda areas, the rainwater retention and infiltration system in Parque Eduardo VII and even a 350-metre tunnel on Avenida Infante D. Henrique, “very close to the Oriente Station”. The person in charge of the drainage plan also mentions “one-off jobs to happen throughout the network”, something that could reach 70 million euros.

“Wanting there to be no floods is a bit like the idea of turning manure into gold. It's alchemy.

We were abusive in our way of using the territory, so now we are going to have to adapt to that”, points out geographer José Luís Zêzere. About the Lisbon Drainage Master Plan, he’s less optimistic than its coordinator. In the expert’s opinion, the effects will be much more effective in mitigating the consequences of rain in the Baixa area than in Alcântara. “Flooding in Lisbon is related to the functioning of small hydrographic basins that disappeared due to construction done on top of them. In these cases, we resort to a heavy structural solution, as is the case with tunnels. But we are talking about work to mitigate the problem, that is what it’s all about,” he concludes.

Suddenly, learning to live with these floods seems almost inevitable. It’s no coincidence that, in Lisbon, areas designed deliberately for flooding have already been planned out. This is the case for Praça de Espanha, a public space requalification that was also used to create a retention and infiltration point. “It’s a floodable area when it rains a lot, similar to what happens in Northern Europe. It prevents a lot of water from leaving and causing floods elsewhere, even allowing it to infiltrate the site itself. Now, with the recent heavy rains, it got completely flooded. And it's just as well because, while it floods there, it won’t flood elsewhere”, says Silva Ferreira. 

​​The square is at crossroads, especially for opinions. During the two December downpours, it got flooded and the waters reached Avenida de Berna. “It partly worked”, points out José Sá Fernandes, who for 14 years carried environmental responsibilities at Lisbon City Hall. “There is a retention basin that was filled, it worked. Except that Praça de Espanha drains to the opposite side, to the tarmac, not to the basin side. And just as well, so as not to pollute what we want to remain as a natural lake. It’s necessary to solve the other side, where there is a lot of water – an enormous water table under Avenida de Berna, for which a solution has to be found. It’s not enough to increase the collectors, more things need to be done ”, he explains.

Is it too hasty to conclude that flooding in Lisbon is a chronic and unsolvable problem? Not if we leave the complex network of underground aquifers and look at the estuary as well. Zêzere highlights the areas of Baixa and Alcântara as being at the confluence of the water lines. “In the future, we will face flooding issues there coming from the Tagus side. We must be extremely cautious. The response to the rise in sea level, by the end of the century, already relies very little on political decisions to mitigate the greenhouse effect, which is not good news for Lisbon. We are talking about a rise that can reach up to 90 centimetres. For a layman, it's not very impressive, but if we add into it the effects of the tides, the storms and something called 'storm surge', we will suddenly have water reaching the National Coach Museum, the CUF Hospital and Praça do Comércio.”

The specialist defends a city at the ready – in the short term, in preparing plans and protocols that allow both the authorities and the general population to know what to do in the face of a flood situation or worsening weather conditions, but also in the long term, in creating an engineering project that stops the advance of the sea and compensates for the increased difficulty that will be draining rainwater in this scenario.

Even without the precision with which it’s possible to anticipate the rise in sea level, climate change also makes it possible to predict the increase in extreme rainfall such as those that occurred in December. “From a precipitation point of view, nothing guarantees that we have already seen the worst that can happen.”