Preparation in Paris is key to be ready for flood of the century

EiD readers will be pleased to know that editing takes place in one of the highest parts of Paris. But, concerns about future flooding are making city officials prepare for the worst. The recent floods were only a wake up calland the problems will be exacerbated by climate change.  Kim Willsher writes an excellent article in The Guardian about the preparations. Interestingly, the new chief resilience officer was appointed six months ago under the Rockefeller Foundation’s 100 Resilient Cities initiative. This shows the importance of international co-operation.

 

It’s when, not if: but will Paris be ready for the flood of the century?

They call it la crue centennale (the flood of the century) and Paris is well overdue one. While the recent scenes of water-filled streets after the river Seine burst its banks caused no end of headaches for the French capital, the rain stopped just short of calamity. But did it also expose just how vulnerable the city is to a true disaster?

Nobody can predict exactly when Paris will suffer the next big inundation – and no one seems sure how bad it will be. “It’s not a question of if there will be a flood but when,” says Colombe Brossel, assistant to the Paris mayor. “And that’s about as much as we know.”

Brossel says her team is “modestly” pleased with its handling of the recent floods, when torrential rains saw the Seine rise to a dangerous 6.10 metres a fortnight ago, sparking transport and traffic chaos. Several parks were shut, one school was evacuated, museums closed and the Louvre relocated priceless works in its basement storerooms.

“It was an atypical situation in that flooding came at the end of spring/beginning of summer, when normally we expect it in autumn to winter,” Brossel explains. “The rapidity of the rising water meant we had to react quicker than expected, but we didn’t have any really bad surprises. The only unexpected part was how quickly the water rose.”

In March the city had carried out a flood simulation exercise which, Brossel says, led to an important innovation when the storm came for real.

“Our protocol drawn up after the simulation was to reunite the ‘crisis cell’ [made up of officials, emergency services, utility companies and other concerned parties] when the river had risen by 5.5 metres. But in the end, we called everyone together at under five metres because we could see the water was rising rapidly. It was a good job we did and was one of the main things we learned; that our plan couldn’t be too rigid.”

The 100-year flood, however, when it comes, will present the city with a far bigger challenge, says Sebastien Maire, Paris’s new chief resilience officer. “What happened recently shows we are not entirely ready. If we are to become resilient the first thing we need to do is to recognise we are not.”

Maire was appointed to City Hall six months ago under the Rockefeller Foundation’s 100 Resilient Cities initiative. He believes that while the city authorities are doing their best, more needs to be done at national level to mitigate the effects of natural disasters and unusual weather events caused by climate change.

“We need to take a more holistic approach to this,” Maire says. “It’s not just Paris’s problem – it’s a problem for the whole country, and it’s for the state to oversee this.”

The haunting reference point for Paris’s flood disaster preparations is, of course, the Great Flood of 1910, an event that scarred the city’s collective memory. In January that year, after weeks of heavy rainfall, the Seine in central Paris rose by 8.62 metres over 10 days. It was the highest centenary flood since 1658, when the river reached 8.81 metres, but in the intervening years the city’s population had increased from under 700,000 to more than 2.8 million.

City roads were submerged by torrents of icy and increasingly polluted water from swollen tunnels, sewers and drains. The metro system – and around 22,000 buildings – were flooded. Daily life for Parisians ground to a halt as basic infrastructure collapsed. Thousands of Parisians were evacuated from their homes to makeshift shelters in schools, churches and administrative buildings. Police, fire services and the army distributed aid to stranded residents by boat.

Nobody died according to the reports, but there were around 150,000 casualties, and cases of typhoid and scarlet fever. The damage was estimated at the equivalent of €1.6bn (£1.2bn) in today’s money – but a modern catastrophe would be far more costly: Hurricane Katrina’s damage to New Orleans was an estimated $96-$125bn.

Since then, Paris’ flood preparation has been based on the 1910 event: a winter flood of around 8.62 metres. But Maire says crisis plans need to look beyond that mark. “We have to ask: what do we do if it’s worse than in 1910? We are more urbanised now and the situation is, above all, aggravated by climate change. And what if it doesn’t happen in winter, as expected?”

The worst surprise during the recent flooding was a “technical failure” of the environment ministry’s flood warning system Vigicrues (“vigilence + crue”). Debris in the swollen river reportedly blocked water-level monitors that then underestimated the height of the Seine by up to 50cm.

Staff at the Hôtel de Ville, sitting on the right bank of the river, were convinced the Vigicrue figures were wrong after someone measured the water using more conventional means – a wooden pole – but the error was not corrected for crucial hours.

As the deployment of batardeaux, movable barrages to protect the quays and highways along the river, is decided on Vigicrue data, city officials were less than pleased.

“If Vigicrue doesn’t work, then all the information we get every day of the year serves no purpose at all,” Maire said. “We needed that information and we didn’t have it because the system broke down, apparently because of debris. It should be obvious that in a flooded river there will be debris, but it appears the system didn’t take account of something that should be obvious.”

Maire advocates a triple approach to the flood threat, that starts with prevention, including removing manmade structures in the floodplains of the 777km long Seine and other rivers, and planting trees and vegetation to act as a sponge.

“Flooding is a natural phenomenon; it becomes a catastrophe because we humans have put ourselves and our infrastructures in the wrong place, so we have to reconquer the major floodplains and get as much vegetation in there as possible,” Maire suggests. “This involves several regions, not just Paris.”

The second is educating local populations: “We have a central state administration, we don’t inform people, we don’t give them a part to play in controlling the crisis which means when something happens, the first thing they do is ring the emergency services. We saw this after the November [terrorist] attacks in Paris when the police telephone system collapsed because so many people rang to ask what was happening.

“You have to tell people straight: the disaster will happen but don’t worry, if you are prepared it doesn’t have to be so bad for you. We also need to encourage the kind of response we saw in recent flooding in places like Nemours where locals spontaneously helped evacuate people without waiting for the fire brigade.”

The third step, Maire says, is the “build back better” principle. A 2014 OECD report suggested rebuilding infrastructure after a centennial flood in Paris would cost at least €30bn. Maire says more studies are needed to draw up a Plan B for post-flood infrastructure to avoid recreating the same mistakes.

After 1910, planners sited the electrical substations and transformers that supply Paris in the floodplains. “We knew what had happened in 1910, we knew about the 100-year floods and we still built these things in areas of major flood risk,” Maire protests.

“The accepted logic of the after-catastrophe period is to get back to normal as quickly as possible, but we must rebuild more robustly. It will cost more, perhaps double, but it’s better than committing the same errors and replicating the same vulnerability.”

While the river Seine has now subsided from danger levels, it remains high due to the wettest spring in the Paris region since records began 150 years ago. Brossel says experts are still monitoring underground infrastructures such as foundations, pipes and tunnels, which can be threatened by increased pressure from the bloated water table.

“Everything looks like its back to normal, but we’ll be working on this for weeks to find out what we can learn from it,” Brossel says. “We remain modest, but we know what we have to do and everyone learned something from the recent flood even if it was 6.10 metres and not the 8.62 metres we know we will have to face.”

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