Detailed guide: The Thames Barrier

Environment Agency

March 25
08:02 2020

The Thames Barrier is one of the largest movable flood barriers in the world. The Environment Agency runs and maintains the Thames Barrier as well as Londons other flood defences.

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Photograph of the Thames Barrier

The Thames Barrier

Forthcoming scheduled closures

The Environment Agency operates the Thames Barrier every month for maintenance and testing, in addition to the annual test at a high spring tide.

The gates may begin closing and re-opening up to an hour before the times listed below:

  • Thursday 13 February 2020 10am to 12:30pm
  • Thursday 12 March 2020 9:05am to 11:35am
  • Monday 27 April 2020 9:50am to 12:20pm
  • Monday 11 May 2020 10:10am to 12:40pm
  • Tuesday 9 June 2020 9:50am to 12:20pm
  • Wednesday 8 July 2020 9:35am to 12:05pm
  • Thursday 6 August 2020 9:25am to 11:55am
  • Monday 7 September 2020 10:25am to 12:55pm
  • Sunday 4 October 2020 9:05am to 7:05pm

Annual full tide test closure

The annual test closure is a unique chance to come and see the Barrier and Gates in operation. During the test, the flood gates will rotate into the fully closed defence position to stop the high tide going upstream into London.

Click here for operational times and further details about the annual closure

Very occasionally, the Environment Agency may need to change or cancel a closure at short notice. Please call the Thames Barrier to check: 020 8305 4188.

Forecasting closures

The Environment Agency receives information on potential tidal surges from weather satellites, oil rigs, weather ships and coastal stations. They can forecast dangerous conditions up to 36 hours in advance, and will close the barrier just after low tide, or about 4 hours before the peak of the incoming surge tide reaches the barrier.

They get information from a range of mathematical computer models that forecast expected sea and river levels. This is supplemented by data from the Met Office and real-time information provided by the UK National Tidegauge Network. This hydrological and meteorological data is fed into the control room every minute from a wide network of tide, river, pressure and wind gauges.

The decision to close, or not, is based on a combination of 3 major factors:

  • the height of the tide (usually a spring tide) measured at the Thames Estuary
  • the height of the tidal surge, which naturally accompanies each tide
  • the river flow entering the tidal Thames, measured as it passes over Teddington Weir

Find up-to-date data for river and sea levels at the Thames Estuary and Teddington Weir.

The barrier has no individual trigger level for closure. The closing process is guided by a mathematical matrix that considers the river flow, tide and surge at the time. The final decision for closure lies with the Thames Barrier Duty Controller.

How the Thames Barrier works

The Thames Barrier spans 520 metres across the River Thames near Woolwich, and it protects 125 square kilometres of central London from flooding caused by tidal surges. It has 10 steel gates that can be raised into position across the River Thames. When raised, the main gates stand as high as a 5-storey building and as wide as the opening of Tower Bridge. Each main gate weighs 3,300 tonnes.

The barrier is closed under storm surge conditions to protect London from flooding from the sea. It may also be closed during periods of high flow over Teddington Weir to reduce the risk of river flooding in some areas of west London including Richmond and Twickenham.

The Thames Barrier will then remain closed over high water until the water level downstream of the Thames Barrier has reduced to the same level as upstream. This is a managed process to provide for different circumstances, and takes about 5 hours. The Thames Barrier is then opened, allowing the water upstream to flow out to sea with the outward-bound tide.

You can watch a video that shows how the Thames Barrier works:

a video of how the Thames Barrier works

Thames Barrier closures

The Thames Barrier has been closed 186 times since it became operational in 1982 (correct as of October 2019). Of these closures, 99 were to protect against tidal flooding and 87 were to protect against combined tidal/fluvial flooding.

Thames Barrier closures since 1983.

Thames Barrier closures since 1983.

If you have an enquiry about the Thames Barrier, or would like to receive a project pack, email:

The future of the Thames Barrier

The Thames Estuary 2100 plan sets out how flood risk will be managed in the Thames estuary to the end of the century and beyond. It also recommends what actions the Environment Agency and others will need to take in the short term (the next 25 years), medium term (the following 15 years) and long term (to the end of the century).

The plan is based on current guidance on climate change, but is adaptable to changes in predictions for sea-level rise and climate change over the century.

More information can be found on the Thames Estuary 2100 page .

Visiting the Thames Barrier

New Thames Barrier cafe and information centre

New Thames Barrier cafe and information centre

Information Centre

The Thames Barrier Information Centre is a small, informative exhibition about the past, present and future of the Thames Barrier. It explains the flood risk to London and the history and environment of the River Thames. There is a working model of the Thames Barrier, a film on the construction, a virtual technical tour film and interactive displays. Last entrance is 30 minutes before closing (see above opening times).

Please call 0208 305 4188 or 0208 854 8028 for information about disabled access.

Thames Barrier Caf and Information Centre closed until further notice

Following government advice regarding coronavirus, we have unfortunately had to close the Thames Barrier Caf and Information Centre until further notice.

Our car park remains open. However, the outside toilets and disabled lift will be locked while the caf and Information Centre are closed.

We will continue to update our website.

If you have any questions please email us at

Opening times

Date Open Last entrance to Information centre Closed
Spring and summer opening to be announced 10:30am 4:30pm 5:00pm
Thursday to Sunday 2 November 2020 to 28 March 2021 11:00am 3pm 3:30pm
Thursday to Sunday 29 March 2021 to 31 October 2021 10:30am 4:30pm 5:00pm

Amended opening hours because of events or bank holidays

  • Saturday 3 October 2020 - Caf closed (Information Centre remains open) due to preparations for Thames * Barrier Annual Closure on Sunday 4 October.
  • Sunday 4 October 2020, extended opening hours (to be confirme

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