Thames Barrier & Information Centre
Rendel, Palmer and Tritton
- Original design
- Rendel, Palmer and Tritton, 1984
The 2017 programme is now past. We will be launching the 2018 programme in July.
The Thames Barrier is one of the largest movable flood barriers in the world.
It protects 125 square kilometres of central London from tidal surges. That’s1.25 million people, historic buildings, offices, power supplies, tube lines, hospitals and more. The Environment Agency runs and maintains the Thames Barrier as well as the capital’s other flood defences. These defences include floodgates like the Barking Barrier and raised river banks.
The Thames Barrier is also one of London’s most striking and famous landmarks. With its distinctive stainless steel piers it spans 520 metres across the Thames near Woolwich. The barrier, which became operational in 1982, has 10 steel gates that can be raised into position across the River Thames if a tidal surge is predicted. When raised, the main gates stand as high as a five-storey building and as wide as the opening of Tower Bridge. Each main gate weighs 3,300 tonnes.
The Barrier is basically a series of ten separate movable gates positioned end-to-end across the River Thames. Each gate is pivoted and supported between concrete piers that house the operating machinery and control equipment.
When we close the barrier we seal off part of the upper Thames from the sea. However, when we’re not using it, the six rising sector gates rest out of sight in curved recessed concrete sills in the riverbed. This means that boats and other river traffic can get through the piers most of the time. When our data forecast a high tidal surge we move the rising sector gates up through 90 degrees from the riverbed. We also bring the four falling radial gates down into the closed defence position. These gates are non-navigable and remain above the river. The ten gates form a continuous steel wall facing down river ready to stem the surge tide.
From bank to bank the Barrier spans about 520 metres. The four main steel-plated gates are massive. They’re over 20 metres high and each one weighs approximately 3,300 tonnes. Each gate can withstand an overall load of more than 9000 tonnes. There are two further gates of similar design, albeit smaller, with 31 metre navigation openings and four falling radial gates that have non-navigable openings next to the river banks that remain above the river.
The gates are moved into position by linkages from two hydraulic cylinders, which move the rocking beam. The linkages work in opposite directions. The rocking beam is raised by the pulling of the upper linkage and pushing of the lower linkage. A connecting link between the tip of the rocking beam and the gate arm transfers the beam movement and makes the gates rotate. The hydraulic cylinders, their associated linkages and rocker beams are located on both side of the gates. The gates can be moved by either side, they do not have to have both lifting, so there is always a back-up arm.
An individual gate can be closed in 10 to 15 minutes but to close the whole barrier for a flood defence closure takes approximately 1½ hours. This provides enough time to check the equipment and stops the potential of a reflective wave. The gates are closed in pairs from the outside into the centre. The ideal situation is for the gates to be closed just after low tide.
The gates are moved into an underspill position to speed up the time it takes to lower the gates after the tide has turned. This position allows a controlled amount of water to pass under the gates up the Thames. The gate can also be placed into a maintenance position. This allows the barrier staff to safety access and service the gates and keep them in good working order.