This Is What Would Happen If London Flooded

TLDR: If the tube floods, we're obviously in big trouble.
Photo: Andrew Aitchison / Alamy Stock Photo

Humans are doing everything they can to make Earth an uninhabitable rock suspended in the middle of a boundless darkness. Until they succeed in that pollutant-driven, climate change mission, we're left to deal with the fallout, which – in London – means hotter, drier summers and warmer, wetter winters. With the increased chance of extreme weather, like heavy rainfall and heatwaves, the possibility of the capital flooding is now a conceivable one – if still fairly unlikely in the short-term.


Luckily, we have defences in place. Operational from 1984, the Thames Flood Barrier – a protection against extremely high tides and storm surges coming from the North Sea – can be closed and raised depending on when it's needed, and spans 3km, from Newham to Greenwich.

Sounds good, sure – but what would happen if this seemingly well-thought out infrastructure suddenly… didn't work? A terrifying thought, I know, so let's explore it.

Could this happen?

David Demeritt is a professor of geography at King's College London, and specialises in flood risk management and climate change. He told me the barrier is beginning to reach the end of its design lifetime, and would cost millions to upgrade. "With sea levels rising, it no longer provides the same protections it was designed for, because the risk is bigger," he says.

This isn't a controversial opinion. In March of this year, the Environment Agency's Chief Executive, Sir James Bevan, praised the city's defence measures, but pointed out that "what works so well now – and has done in the past – may not be enough in the future. Over the next 50 years, if we are going to give the country the best possible protection against flooding, we are going to need a different approach."

While this is a pressing fear, Jane Barraclough from the Environment Agency reassured me they're on it. "We're already planning for climate change – the Environment Agency builds climate change projections into the design of flood defences to make sure they are fit for the future," she said.


Still, what would happen if the defences failed?

The Thames River Barrier. Photo: Julio Etchart / Alamy Stock Photo

While the Environment Agency found it tricky to speak about hypotheticals, Demeritt was more than happy to. He told me the biggest concern in such a scenario is the Tube flooding. Not only is this likely were widespread flooding to occur for any reason, but the damage done would be substantial and long-lasting, since London's stations have taken no precautions against it.

"Your worst case would involve flooding of the underground stations, which would shut the network. Because the tunnels are deeper than in NYC, it would be messier and more difficult to clean out than after Hurricane Sandy," he said.

Hurricane Sandy was the most destructive hurricane of the 2012 Atlantic hurricane season, resulting in damages of around $70 billion (£53 billion). The storm surge hit New York City in October of 2012 and flooded streets and subway lines; it cut power in and around the city, and all ten subway tunnels in lower Manhattan were damaged. The Tube is obviously such a huge part of how London runs that this could theoretically cause absolute chaos were it to happen.

What about business and the knock-on effects worldwide?

In light of London's role in the many global supply chains that keep our economies going, there would undoubtedly be a knock-on effect, says Demeritt. Bangkok’s flooding in 2011 is a prime example of this; killing 815 people and lasting 175 days, the floods led to 65 of Thailand's 76 provinces being declared disaster zones.

Aside from ravaging the country's landscape, like Sandy, it cost it huge amount of money to bounce back from. The World Bank estimated 1,425 trillion baht (£32.7 trillion) in economic damages and losses. In fact, they suggested the disaster was the world's fourth costliest as of 2011 (this list included the 2004 Indian Ocean tsunami, Hurricane Katrina in 2005 and the Chilean earthquake in 2010).

Thailand was the second largest producer of hard disk drives, and supplied 25 percent of the world at the time. Post-flood, many of the factories that made these drives were ruined, which led directly to hard drive disk prices almost doubling across the world. That one market took two years to recover.

Of course, the UK's isn't exactly a leading figure in computer components; banking is its major industry. "I'd expect [the banking industry] to a) have a pretty robust business continuity strategy, and b) insurance that will tend to spread and buffer the economic costs of disruption," says Demeritt.

It seems that while the idea of London flooding is plausible – although not all that likely, thanks to our hero, the Thames Flood Barrier – the clearest losses would be an unprecedented amount of money and damage to industries and transport. Barraclough reiterated that if you really want to know more, Environment Agency offers free flood warnings – who knew.