Thames Barrier Hydraulics Save the London from Flood

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Thames Barrier Hydraulics Save the London from Flood

Are you familiar with the Thames Barrier in London? You may be! Because the Thames Barrier is the World’s second-largest movable flood barrier located on the River Thames, London, United Kingdom. This moveable flood defense at the east of Canary Wharf has a structure of giant conch shells rising out of the water. The Thames Barrier started operation from 1984 onwards and this structure has a height of 20.1m and a length of 520m. This structure was built by Costain and is currently operated and maintained by the Environment Agency.

Why is Thames Barrier so crucial for London? In 1953, the North Sea flood hits London, killing over 300 people and also destroying more than 160,000 acres of farmland. This unique flood control structure was constructed to protect 48sq miles of London and 1.25 million people from floods, that are caused by high tides and storm surges. When it was developed, it was expected to smoothly function until 2030. But, now the studies state that this barrier will be operable till 2060/2070 when maintained properly.

When to operate the Thames Barrier? As mentioned, this huge infrastructure is operated and maintained by the Environment Agency with an aim to prevent the flood. The important factors that need to be considered for making decisions regarding when to close this barrier include the height of the tide, the height of the tidal surge, and the entering river flow. The information regarding potential tide surges will be forecasted from weather satellites, coastal stations, weather ships, and oil rigs to the Environmental Agency at least 36 hours in advance. Different mathematical computer models are also used for forecasting expected sea and river levels.


The construction of the Thames Barrier started in 1974 and from 1984 onwards this movable barrier is protecting Britain’s capital city from tidal flooding. This 520m long structure consists of 10 separate movable steel gates each with a hollow steel platted structure. This overall design includes four 61m and two 31m rising sectors, and four falling radial gates of 31m. Over 9000 tonnes of water load can be safely handled by these steel gates.

In non-flood conditions, the floodgates with circular segments will lie flat on the river bed. The curved recessed concrete cills will hold the floodgates in the riverbed. When the barrier is open, it will allow the free flow of water without any restriction and also the passage of water traffic. The lifting mechanism of the floodgate is controlled by hydraulics and it consists of components like hydraulic cylinders, rocker beam, and rocker link.


The Thames Barrier is operated only when there arises the risk of flood and it can have three operating positions; open, closed, and underspill position. When it is opened, the gate will be submerged in the riverbed and it can allow free passage of water traffic. Under closed position, the solid steel wall will prevent the upstream flow of water towards the capital. The gate will be closed just after the low tide or 4 hours before the incoming surge tide, and it takes approximately 75-90 minutes for closing all the floodgate. The underspill position will allow only a controlled flow of water through the gate.

The operators of the Environmental Agency will operate the floodgates of the Thames barrier from the nearby control building. This electrically driven floodgate is operated by three 140kW hydraulic power packs. Each of the movable gates will contain a separate lifting mechanism and hydraulic system. The two hydraulic cylinders inside the system will control the movement of the gate that is connected to the rocker beam with a rocker link. It is the pressurized hydraulic fluid that helps to extend and retract the cylinders independently to adjust the position of the floodgate as per the requirements.

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