London floods are the latest sign that big cities are unprepared for climate change

(CNN) – Cars stranded in the streets turned into rivers. Bus passengers rescued by raft. Submerged train stations, causing road chaos.The familiar scenes of a flooded city were repeated in London over the weekend, when heavy rains left parts of the British capital under water.

The fact that two London hospitals turning away non-emergency patients after flooding over the weekend was a brutal reminder that even some of the world’s richest cities are dangerously ill-prepared for the kind of extreme weather that is becoming more common and more severe. due to climate change.

Climate and infrastructure experts have been warning for years that London, like many other big cities, is not prepared for climate change, with large parts of the city built on a floodplain and a Victorian drainage system that is not capable. to withstand this type of heavy rain.

“It is very worrying that we have to close the emergency services of the hospitals because they have been flooded, certainly something must be done to ensure that critical infrastructure is not at risk,” said Liz Stephens, associate professor in the department of geography and environmental science from the University of Reading.

According to the London Metropolitan Authority, 17% of the city faces a high or medium risk of flooding, and more than a million Londoners live on a floodplain.

The city has a gigantic flood defense system on the River Thames to protect itself from rising tides, but barriers are of little help when it comes to flash floods caused by heavy rains, the kind that is becoming more common due to rising temperatures.

Footage from Sunday showed Londoners taken by surprise, wandering the flooded streets. Some even tried to drive away through the rising waters, something authorities advise against because of the high likelihood of cars being swept away or drivers being trapped.

The London Fire Brigade said on Monday it handled more than 1,000 flood-related emergency calls, and crews rescued people from their cars and helped them escape from their homes.

Although these images of people not taking risk seriously are concerning, Stephens said individuals are not at fault in this case.

“Our ability to map surface water flood risk is not particularly good,” Stephens said. He noted that UK surface water flood risk maps have not improved significantly since 2013, despite more precise technology being available and numerous reports have been published highlighting the increased risk.

Furthermore, the way to monitor and manage flood risk in the UK is extremely complicated, with different agencies responsible for different parts of the effort and no single agency in charge.

The Met Office, the UK’s national weather service, issued weather advisories for heavy rain and storms on Sunday, but Stephens said people may not immediately understand them.

“I think there was an amber warning indicating there could be severe impacts, but the amber warning covered a very large area of ​​south-east England,” Stephens said. “So really, as an individual, what would you do with that kind of information. If you don’t know that your property is at risk of flooding, and you have a full-scale flood warning, or not even a flood warning, a rain warning? intense, so I don’t think we should be surprised if people aren’t ready for it, “he said.

A report on the impacts of climate change in the UK, released last month by the government’s independent climate advisory group, the Committee on Climate Change, warned that the country was unprepared, stating that ” adaptation have not kept pace with the increasingly dire reality of climate risk. “

“The risk is always higher in the urban environment because we have paved surfaces, but we also rely on an old drainage infrastructure in London, we are talking about Victorian drains,” Stephens said.

Images like the ones that arrived from London on Sunday are becoming worryingly familiar.

Just two weeks ago, devastating floods from heavy rains swept across large parts of Western Europe, leaving more than 200 dead and thousands homeless. At the other end of the world, much of the central china Henan province was devastated by record rains last week, which killed at least 58 people, cut off power and forced more than a million people to relocate.

And although it is not possible to attribute a single event to climate change, heavy rains and floods are becoming more frequent. As Earth’s atmosphere warms, it can retain more moisture, which can lead to unprecedented rainfall. It may be that the total average rainfall in an area does not change, but the extremes are amplified, which can mean longer dry spells or more intense storms. When it rains heavily after a prolonged drought, soils are less able to absorb water and rain is more likely to cause flooding.

Urban areas are at higher risk of flash floods because the surfaces are covered with concrete, which means that the ground cannot absorb the water. According to the European Environment Agency, Paris, Thessaloniki, Bucharest and Barcelona are among the cities with more than three-quarters of their area “sealed”, which means they are at the highest risk of flooding.

Furthermore, many European cities have very old infrastructure and sewage systems cannot cope with the heaviest rains.

“Summer storms are nothing new, but it is becoming increasingly clear that the worsening impacts of flooding from heavy rains are having devastating effects here in the UK and across Europe,” said Jess Neumann, hydrologist at the University of Reading, in a comment to the Science Media Center. “The severity and frequency of the floods are a stark warning that we are not prepared to deal with climate change.”