How does the Thames Barrier protect London?

The Thames Barrier is the second largest movable flood barrier in the world and plays a major role in protecting the capital of England, London. While many people take the massive construction project for granted it has literally saved hundreds if not thousands of lives over the years and protected the centre of London from serious flooding. The barrier itself is located in the area of Silvertown in the London Borough of Newham (northern bank) stretching over to the southern bank in the New Charlton area in the London Borough of Greenwich.

Why is the Thames Barrier required?

It may not be common knowledge but London has over the years been very susceptible to significant storm surges generated by low pressure in the Atlantic Ocean. These storm surges can begin as far away as Scotland driving massive volumes of water into the English Channel and potentially up the Thames Estuary. On a number of occasions we have seen high tides coincide with substantial storm surges resulting in significant pressure on the water flowing out of the Thames. This is the signal for the Thames Barrier to be raised and potentially stop a disaster in the making.

The building of the Thames Barrier

The project began in 1974 and the particular areas of the river were chosen because of their underlying chalk bed which was able to support the massive barrier and the supporting towers. The project had been delayed from the 1960s when concerns were raised after the serious 1953 North Sea Flood which saw 307 people die when a massive tidal surge caused serious damage in England, Belgium, Denmark and France although the Netherlands took the brunt of the disaster with nearly 2000 deaths reported. This particular tidal surge saw sea levels rise by nearly 6 m above the average causing massive inland surges which knocked out many towns and cities on the coast.

While the 1953 North Sea Flood did not directly affect London it brought about a serious review of the U.K.’s sea defences with London receiving particular attention. The last major flood to affect London was the 1928 Thames Flood which saw 14 people die with Westminster literally knee deep in water, such was the force of the tidal surge which rolled all of the way up the Thames into central London.

The construction itself is built across a 572 yard stretch of the Thames which is separated into four 200 feet lanes and two smaller shipping lanes with an additional four non-shipping lanes between the nine concrete piers and two abutments. The gates themselves are submerged underwater and when not in use lie flat on the riverbed to allow a clear path for shipping in the region. The sections of the gate themselves are hollow and made of 1.5 inch thick steel with the four large gates in the centre of the river, 220 feet long and 35 feet high (above local ground level) with each one weighing a massive 3500 tonnes. The two outer gates are 100 feet in length and also 35 feet high in order to keep the barrier level across the river.

While the majority of the project was finished in 1982 it was first used for defensive measures in 1983 and officially opened in 1984. The Thames Barrier was approximate 10 years behind schedule and cost £534 million with an additional £100 million spent on further river defences in the region.

How does the Thames Barrier work?

When not in use the Thames Barrier lies flat on the riverbed parked within a curved area specifically carved out the riverbed. Within approximately 30 minutes the Thames Barrier can be fully operational with the massive steel construction rising 90° from the riverbed to withhold a potential tidal surge and contain the natural flow of the Thames behind the immovable steel gate. There is also the potential to control any potential down surge from the Thames via an under-spill position which will allow the level of the river to be regulated before the gate is returned to its parked position.

Each time the Thames Barrier is raised the massive hydraulic pumps used to move the steel barrier are said to use in excess of £5000 worth of electricity within the 30 minute period. The length of the gate across the river is actually half the size of the Eiffel Tower and thankfully the gate has never been breached, with no tidal surge ever coming within 7 feet of the top of the gate.

What does the Thames Barrier give to London?

The Thames Barrier is literally the lifeline of London and when initially constructed it was estimated that it would work at full power and offer full protection for around 100 years. However, projections for sea level rises around the world have increased over the last few years with global warming taking effect and it is now estimated that the level of protection afforded to London will start to diminish after 2060.

Without the Thames Barrier the centre of London would be in serious danger especially when you consider that prior to 1990 the gates were closed on no more than two occasions per year on average. This figure increased to 4 times a year between 1990 and 2000 and has reached around 10 times a year today. It is also worth noting that in 2003 the barrier was closed for a record 14 consecutive tides although the most serious tidal surge of recent times occurred on 9 November 2007 when the barrier was closed two times in one day with weather data indicating a surge heading for the Thames which was comparable with that of the 1953 disaster.


While the Thames Barrier may well have to be updated or possibly replaced over the coming years it offers a massive degree of protection for London and the surrounding areas. In line with most major cities around the world, London is based around shipping and the Thames Estuary, which has left the capital susceptible to major flooding for hundreds of years.

The barrier was designed by Rendel, Palmer and Tritton with Charles Draper taking credit for the rotating gates which were revolutionary in their day. While it is difficult to estimate the potential damage to London if the Thames Barrier was not there, some analysts have suggested a cost figure as high as £20 billion if a major flood were to hit central London. The Thames Barrier does not receive an awful lot of press and many people in the more northern parts of the UK may not even be aware of the construction but many of those in and around the London area literally owe their life to this monumental barrier.

8 Responses to “How does the Thames Barrier protect London?”

  1. Yes, but how does the barrier contain the stopped water? Why does it not just overflow the non-raised banks and flood London – perhaps even sooner than if the dam was not there?

    • Yes, to maintain the water level in the Thames in the important areas when extraction and over population have their way. The water backs up against the dam as it flows down and so lets the level rise. A dam always makes the water level rise and dams are used to create reservoirs behind them. As the Barrier was designed and built while we were in a global cooling period (1945-75 + 10 years hiatus before the warming period began) and rising sea levels hadn't been cinsidered, it can't have been that. I am waiting for a reply which explains to me how a dam with no side containment can possibly work – how a dam can be used as flood prevention at all. I may have missed something here so I need a detailed explanation of how the dam prevents flooding. There is no such explanation in any of the many websites I have looked at (including the Environment Agency's), there is no such information.
      I await with interest a detailed explanation.

      • Mr. French

        The banks have been raised downstream because the water has come up seven feet below the top of the barrier which is well above land level and sea wall level.

  2. Interesting! A raised bank would have to be constructed all the way from the Barrier on both sides of the river to the Estuary and along its coast. This is a massive engineering task of which not a single mention can I find, nor remember being in the news. Please post pictures of this and let me know where they (the pics) are. I have carefully studied all the pictures I can find and the raising of the bank completely escapes me. Also there is no picture of the water level being very high ( higher than the normal banks on the upstream side), and 7' from the top of the Barrier gates. I would have thought this would be the most 'sexy' type of pic possible. Of course the Barrier is in the wrong place as all other storm-surge barriers have been constructed across the mouth of a river, or even the mouth of its Estuary where that is possible. Evidence amounting to proof, not words, is what I need.

  3. I have the exact same questions as M Smith. That's how I came to be here. I'm not one for conspiracy theories so I gather there must be and explanation to this but I'm yet to find one. If anyone can put forward some useful info it would be appreciated.


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