St Petersburg is under threat from the sea; its new flood barrier will protect it for centuries.
In certain weather conditions over 5km of water could surge through the Gulf of Finland, into Neva Bay, and swamp St Petersburg.
Thanks to a £1.8bn major infrastructure project to construct a 25.4km barrier across Neva Bay that threat is receding day by day. By the end of next year the city should be protected for centuries to come.
The barrier consists of a 6.5m high embankment running from Bronka in the south to Gorskaya in the north. Two major navigation channels − known as S1 and S2 − are each protected by huge steel gates that can be closed quickly when a surge is threatened.
Flow and movement
Water flow between Neva Bay and the Gulf of Finland is also aided by six sluices up to 300m wide and equipped with their own steel gates that can be shut to keep out a surge wave.
Running along the top of the barrier is a six lane motorway that is the latest link in the St Petersburg ringroad. This highway crosses the smaller navigation via a lift bridge that can be raised 9m to allow local shipping to pass beneath. At navigation S1 the road disappears into a 2km long, 26m deep tunnel under the navigation channel.
Completion of the scheme, which started in 1979 but was halted for 15 years by the end of the Soviet era, is scheduled for the end of 2010.
St Petersburg flood barrier: Saving the Saint