Environmental management – guidance

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.

Photograph of the Thames Barrier
The Thames Barrier

Upcoming 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.

  • Wednesday 11 March 2015, 9:40am to 12:10pm
  • Tuesday 7 April 2015 9:25am to 11:55am
  • Thursday 7 May 2015 9:35am to 12:05pm
  • Thursday 4 June 2015 8:45am to 11:15pm
  • Monday 20 July 2015 10:00am to 12:30pm
  • Tuesday 18 August 2015 9:35am to 12:05pm
  • Sunday 27 September 2015 6:30am to 16:30pm (full annual test closure)
  • Monday 19 October 2015 10:45am to 1:15pm

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. You can find out if the Thames Barrier is currently closed by calling Floodline on 0345 988 1188 and using the quickdial code 011134.

Follow us on Twitter: @AlanBarrierEA

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.

The Environment Agency has closed the Thames Barrier 174 times since it became operational in 1982 (correct as of March 2014). Of these closures, 87 were to protect against tidal flooding and 87 were to alleviate river flooding. The frequency of closures has increased over recent decades:

  • In the 1980s there were 4 closures
  • In the 1990s there were 35 closures
  • In the 2000s there were 75 closures
  • In the 2010s there were 65 closures (as of March 2014)
Graph showing Thames Barrier closures since 1983
Thames Barrier closures since 1983

You can watch a video of how the Thames Barrier works:

a video of how the Thames Barrier works

If you have an enquiry about the Thames Barrier, or would like to receive a project pack, email: kslenquiries@environment-agency.gov.uk

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

It is open to the public from 10:30am to 5pm, Thursday to Sunday (last admission is at 4:30pm). Carers accompanying disabled visitors are admitted free of charge.

Find more information on prices for the Thames Barrier Information Centre - April 2014 - March 2015 (PDF, 76.1KB, 2 pages) .

Find more information on prices for Thames Barrier Information Centre - From April 2015 (PDF, 195KB, 2 pages)

Find more information on dates for group talks 2015 (PDF, 55.4KB, 1 page) .

You can also arrange group visits by filling in this booking form (MS Word Document, 209KB) and emailing it to: learningcentre@environment-agency.gov.uk.