The Thames Barrier protects millions of people and billions of dollars worth of property in greater London from flooding. As a New Yorker who experienced Superstorm Sandy and its record storm surge first hand, I made a point to visit this crucial piece of engineering during a recent trip to the UK.
Completed in 1982 at the cost of £535 million (about £1.6 billion today), the barrier was built in response to the catastrophic North Sea Flood of 1953. Often called the worst natural disaster to hit the UK, the floodwaters claimed the lives of 307 people and caused widespread damage estimated at £50 million (£1.2 billion today).
According to the UK Met Office, the deadly flood was caused by the combination of a high spring tide and an intense extra-tropical storm in the North Sea. Together, they generated a storm surge of 18.4 feet above average sea level. Moving upstream during the overnight hours of January 31, 1953, the high water overwhelmed the existing floodwalls and inundated communities along the Thames Estuary with little or no warning.
Situated downstream of central London, the barrier consists of ten individual steel gates that span a section of the river that is 1700 feet wide. It is the second largest movable flood barrier in the world, after the Oosterscheldekering barrier in the Netherlands. The Netherlands were also hard hit by the 1953 storm, with over 1800 lives lost to floodwaters.
When a storm surge or an exceptionally high tide is expected, all of the individual gates of the Thames Barrier are closed creating a solid steel wall, approximately five stories high, across the river. While this protects London from flooding from the sea, the barrier can also be used to help reduce fluvial flooding caused by heavy rainfall. When a high amount of water is forecast to flow downriver, the barrier is closed just after low tide. This creates a volume of space behind the barrier – sort of like a temporary reservoir – for the extra water coming downstream to fill. Without the barrier, the incoming tide would take up this space and cause the river water to rise even higher and spill out of its banks.
To date, according to the UK Environment Agency, the Barrier has been closed 176 times since it became operational 34 years ago. Of these closings, 89 were to protect against tidal flooding and 87 were to help alleviate fluvial flooding. At the time it was built, it was only expected to be used 2 to 3 times per year.
Looking ahead, as the climate warms, heavy precipitation events in the UK are expected to increase and sea levels will continue to rise. This means the barrier will most likely be called into action even more often.
While there was debate about the feasibility and cost of building the barrier, as there is with any large government project, it has repeatedly proven itself to have been a worthwhile investment. It is expected to remain a viable flood defense tool through the 2060’s.
The Thames Barrier protects London from flooding. Credit: Melissa Fleming.