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.
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.
- 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.
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
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:
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: email@example.com.
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
Please note that the disabled lift is currently out of action; it will be fixed as soon as possible.
The newly refurbished Thames Barrier Information Centre is now open. For more information call 0208 305 4188.
The centre has an additional conference room and improved outdoor seating area, which allows the Environment Agency to offer more availability for group talks and conferences. This new room has additional cover for winter group talks.
Thames Barrier price list
Thames Barrier conference rooms leaflet
Once a month you can pre-book onto guided tours 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.
We are now offering a group tour with afternoon tea
Group talks are £6 per person and full payment is required in advance when you call to book your date. To book, email firstname.lastname@example.org or call on 0208 305 4188.
You can also arrange larger group visits (for more than 5 people) by filling in this email@example.com emailing it to