Not that far from London, the River Thames flows into the English Channel, and here, downstream of the city, the river is dramatically affected by tides. There can be a difference of as much as 22 feet in the level of the river between high and low tide. Normally, this isn’t a problem, but when rainfall upstream swells the Thames, the combination of changing tides and flood waters could be disastrous.
But the Thames Barrier, which was built in 1982, protects the city. With its alien-looking metal domes perched above the water, the barrier has become an iconic piece of London’s infrastructure. It features ten steel gates weighing 3,000 tons each that can be raised when needed to defend London from floodwaters.
The Thames Barrier uses the changing water levels to its advantage. When floodwaters are expected to clog the river, those ten steel gates are raised during high tide, keeping the tidal surge out of the city, and allowing the water from upstream to flow safely into the space normally occupied by the tidal waters. When the tide goes out, the barriers come down, and the water can flow safely into the sea.
This winter, with all the rain that's been pouring down on England, the barrier has been doing its work. It closed for a record fifty times this winter. The last time the Thames Barrier set a record for closures, in the winter of 2000-2001, it closed half that much—a relatively small 24 times.
This year, more closures have happened in February alone, with 28 for the month. Originally the barrier was designed to last until 2030, but the people that run it hope that a replacement won’t be needed until 2070. If you want to see it in person, (or are a really big Dr. Who fan) you can visit the barrier, though you will have to pay for admission. But it might be wise to wait until the rain lets up, just a little.