The Thames Barrier

How the Thames Barrier works, and when it is scheduled to close.

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 London’s other flood defences.

You can follow us on Twitter @AlanBarrierEA or read our blog posts. or like our Facebook page

Photograph of the Thames Barrier
The Thames Barrier

Forthcoming scheduled closures

The Environment Agency operates the Thames Barrier every month for maintenance and testing. Once a year, they also test the barrier at a high spring tide (normally September or October). They may begin closing and re-opening the gates up to an hour before the times listed below.

  • Tuesday 20 February 2018 09:30am to 12pm
  • Thursday 22 March 2018 09:35am to 12:05pm
  • Thursday 19 April 2018 09:50am to 12:20pm
  • Thursday 3 May 2018 09:30am to 12pm
  • Monday 4 June 2018 10:35am to 13:05pm
  • Monday 2 July 2018 09:45am to 12:15pm
  • Wednesday 1 August 2018 10:10am to 12:40pm
  • Sunday 23 September 2018 6:25am to 4:25pm (annual full tidal test closure)
  • Thursday 11 October 2018 9:15am to 11:45am

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 182 times since it became operational in 1982 (correct as of February 2018). Of these closures, 95 were to protect against tidal flooding and 87 were to protect against combined tidal/fluvial flooding.

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

The Thames Barrier Information Centre is currently closed for refurbishment, which is due to be finished in June 2018.The re-opening date will be published on this page. For more information, call 0208 305 4188.

The Thames Barrier Information Centre is a small exhibition centre where you can learn how the Thames Barrier was designed and built, and how it works.

When the centre reopens in 2018, it will have an additional conference room and improved outdoor seating area, which will allow the Environment Agency to offer more availability for group talks and conferences. This new room will also allow additional cover for winter group talks.

Group talks

Once a month, you can pre-book onto guided group talks (PDF, 121KB, 1 page) at the Thames Barrier. Please note, due to security, there is no access onto the Thames Barrier structure itself. It is not suitable for children under the age of 5. This offer is not available to groups over 5 people.

Group talks are £6 per person and full payment is required in advance when you call to book your date. To book, email or call on 0208 305 4188.

You can also arrange larger group visits (for more than 5 people) by filling in this booking form (MS Word Document, 628KB) and emailing it to

Published 25 April 2014
Last updated 16 February 2018 + show all updates
  1. New dates for test closures added.
  2. Refurbishment of cafe delayed until June 2018.
  3. Numbers of closures updated.
  4. Two closures added to closure total.
  5. Correction to barrier closures.
  6. Information on the refurbishment of the Thames Barrier Information Centre and cafe.
  7. Data update 10 October 2017.
  8. Information about finding out if the Thames Barrier is closed via Floodline removed as service is no longer available.
  9. Thames Barrier Annual closure event information removed.
  10. New test closure dates, Cafe closing for refurbishment dates changed and warning to users of wheelchairs at the Annual Closure about access to river bank.
  11. Cafe opening at 9am on the Annual Closure day.
  12. Cafe opening times updated
  13. New information on Thames Barrier Annual Closure
  14. New times added for cafe and information centre.
  15. Taken out that the disabled lift is broken as now fixed.
  16. Information on disabled lift being out of order.
  17. New dates for Thames Barrier closures and group talks added
  18. Notice that the Information Centre will be closed between 30 October 2017 and 28 January 2018 for refurbishment.
  19. Updated opening times to cafe and Information Centre, new group talks dates added
  20. Tall ships dates and the 2017 Thames Barrier annual closure date added.
  21. Cafe opening times updated.
  22. Updated information on group talks
  23. New opening times added.
  24. New information added.
  25. November to March closure dates and information about the Open Day on 2nd October added.
  26. Updated closure dates.
  27. Special offers for Father's Day at the Information Centre.
  28. New group bookings added.
  29. New Thames Barrier Information Centre group talk dates, price list and booking form added.
  30. Notice of event at Information Centre.
  31. Annual closure times for 2016 added.
  32. Updated timetable for group talks.
  33. Visiting the Thames Barrier section has been updated.
  34. Details added about the annual closure.
  35. Details on the annual closure have been added.
  36. Updated closure times and group talk sessions.
  37. In summer 2015, the Information Centre is open 7 days a week during the school holidays.
  38. The test closure dates have been updated, and there is a new link to our blog posts.
  39. New information for group tours of the exhibition centre.
  40. New Barrier closure information.
  41. Updated planed closure dates
  42. Thames Barrier Information Centre prices from April 2015.
  43. Information on group talks added.
  44. Updated 'forecasting closures' section.
  45. Added new closure dates for 2015.
  46. First published.