London is prone to severe flooding, like the disastrous 1928 Thames flood that displaced thousands, and the notorious 1953 North Sea storm that killed over 2,000 people throughout Europe. By far the biggest event was 1953, and it's the biggest natural hazard to affect the UK sort of in the last 200 years. Since then, this region hasn’t experienced such catastrophic floods, mainly due to this: the Thames Barrier, a storm surge defense system that opened in 1984. The barrier, which stretches for a third of a mile across the Thames at Woolwich, is the largest structure of its kind in the world. So, how has the Thames Barrier protected London for this long? And in a world where flooding is more and more common, how will the Thames Barrier adapt to keep up? The Thames Barrier is unique. It's the first movable barrier ever built in the River Thames and protects the most populous part of London.

As the second largest movable barrier in the world, it’s made up of 10 steel gates that span 520 meters across this river. The outer four gates always have their barriers up and closed. And these central, larger six gates are left open most of the time to let ships pass through and for the river to flow naturally. So what triggers the closing of the rest of the barrier? Another storm batters the United Kingdom. Severe weather is not going away. The UK's environmental agency, which monitors the North Sea's tide levels, river flow, and weather, gathers data on a daily basis to determine whether to open or close the barrier. When the decision is announced, the gates can begin closing. It takes about 90 minutes to close all the gates, which can go as high up as 20m. And they’re designed to withstand over 9,000 tons of gushing water.

which is the equivalent of 
almost 118 large swimming pools. The gates remain closed for 
high tide for about four to five hours. Once the flood recedes, the gates are 
lowered to their resting position. The general idea is that the gates block 
the gushing water to protect the city. The Thames Barrier alone protects 1.42 million people, 320 billion 
pounds of residential properties. We had a very, very big storm in 
2013, Storm Xaver. No one died, and one of the reasons why 
that was was because of forecasting, but also as a direct result of these 
storm surge barriers being built. In the year of Storm Xavier, the barrier 
was closed 50 times. For perspective, in the entire decade of the 80s, it 
was closed a total of four times. The more the barriers open and 
close, the faster they deteriorate. And experts fear that climate change will 
disrupt tide predictability in the UK.

Sea level rise is the most certain and probably the most costly consequence of climate change. And we've already seen a 25 centimeter increase in sea level over the last 100, 120 years. To prepare for that getting worse, the UK put together the Thames Estuary 2100 plan: A plan to upgrade London’s flood defense systems that recognizes that we don’t actually know how bad climate change is going to get. And it was a very novel, very unique plan in that rather than sort of just a static adjustment to account for sea level rise, they actually took an adaptive approach and they said, look, we don't know exactly what the future holds. We're going to put a series of plans in place that can adapt. So we know we need a new Thames Barrier, but we don't know exactly when. We think we need a new barrier in 2070.

but if sea levels rise faster than normal, we 
can bring that plan forward. The Thames Estuary 2100 plan 
ultimately comes in three phases. From now until 2035, the main priority 
is to maintain what exists already, like the Thames Barrier, by ensuring it can 
still withstand the pressure of high tides. The plan acknowledges that we don’t yet know how 
much higher they’ll need to be raised, and leaves room for variability. After 2070, the third phase will again examine 
the effects of climate change on London; if water levels are increasing at alarming rates, more interventions like 
additional barriers may be added. The success of the Thames Barrier has 
inspired the creation of more than 50 additional flood barriers around the world, 
protecting millions of people from disaster. But according to experts, the most 
impressive part isn’t the Thames Barrier itself, but the UK government's 
willingness to adapt for the future.

And now countries all around the world are sort of copying that approach from small towns to big cities like New York, and taking this more sort of adaptive approach. And that was very much pioneered in London.

The giant metal walls keeping London above water

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