Thames Flood Barrier

Lonely Planet review

The sci-fi looking Thames Flood Barrier is in place to protect London from flooding, and with global warming increasing the city's vulnerability to rising sea levels and surge tides, the barrier is likely to be of growing importance in coming years. Under construction for a decade and completed in 1982, the barrier consists of 10 movable gates anchored to nine concrete piers, each as tall as a five-storey building.

The silver roofs on the piers house the operating machinery to raise and lower the gates against excess water. They make a surreal sight, straddling the river in the lee of a giant warehouse. Just opposite on the north bank of the Thames is the seven-hectare Thames Barrier Park.

The reason London needs such a flood barrier is that the water level has been rising by as much as 60cm per century, while the river itself has been narrowing; in Roman times it was probably around 800m wide at the site of today's London Bridge while now it's barely 250m, with constant pressure to develop the foreshores. The Thames tide rises and falls quite harmlessly twice a day, and once a fortnight there's also a stronger 'spring' tide. The danger comes when the spring tide coincides with an unexpected surge, which pushes tons of extra water upriver. The barrier has been built to prevent that water pouring over the riverbanks and flooding nearby houses. Some 300 people were drowned on the east coast and the Thames Estuary in 1953 when the Thames burst its banks. Today environmentalists are already talking about a bigger, wider damming mechanism further towards the mouth of the river, before the current barrier comes to the expected end of its design life in 2030.

The barrier looks best when it's raised, and the only guaranteed time this happens is once a month, when the mechanisms are checked. For exact dates and times, ring or check the website of the Thames Barrier Information Centre (www.environment-agency.gov.uk).

If you're coming from central London, take a train to Charlton from Charing Cross or London Bridge. Then walk along Woolwich Rd to Eastmoor St, which leads northward to the centre. If you're coming from Greenwich, you can pick up bus 177 or 180 along Romney Rd and get off at the Thames Barrier stop (near the Victoria Pub, 757 Woolwich Rd). The closest tube station is North Greenwich, from where you can pick up bus 472 or 161.

Boats also travel to and from the barrier, although they don't land. From Westminster it's a three-hour round trip; from Greenwich it takes just one hour. From April to October direct services run by Thames River Services (www.westminsterpier.co.uk) leave Westminster Pier on the hour from 10:00 to 15:00 (leaving Greenwich from 11:00 to 16:00 ), passing the O2 (Millennium Dome) along the way. From November to March there's a reduced service from Westminster between 10:40 and 15:20 . See the website for exact times.