St.Petersburg Dam - South section (Saint Petersburg)

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The Saint Petersburg Flood Prevention Facility Complex (Russian: Комплекс защитных сооружений Санкт-Петербурга от наводнений), unofficially the Saint Petersburg Dam, is a 25-kilometer complex of dams for flood control under construction near Saint Petersburg, Russia, from Lomonosov to Kronstadt and Sestroretsk. It is intended to protect Saint Petersburg from storm surges.

The dam is being constructed across the Gulf of Finland, with the island of Kotlin (Kronstadt) at its center. It extends for 25.4 kilometers and stands eight meters above water level. It has two large openings for shipping, which can be closed when floods threaten. Construction began in 1980 and stalled in the political and economic upheavals of the 1990s. The main benefit that most people cite is not flood control but for traffic, as it will complete a ring road around Saint Petersburg.

Saint Petersburg suffers from frequent floods (289 in recorded history), some being natural disasters. It is on drained marshlands, isles and lowlands in the estuary of the Neva River, where flooding is common. Flow from Lake Ladoga is significant and the Neva's current is rapid, but flooding is generally caused by water backing up the Neva from its outlet, the Gulf of Finland. Most rivers flood in periods of exceptionally high flow, but the Neva typically floods in late autumn.

In the early literature, high winds from the Gulf of Finland were frequently given as the cause of Neva flooding, but scientists now understand the more complex hydrometeorological chain of events behind it. A low-pressure region in the North Atlantic moves onshore, giving rise to cyclonic lows on the Baltic Sea. The low pressure of the cyclone draws greater-than-normal quantities of water into the virtually land-locked Baltic. As the cyclone continues inland, long low-frequency seiche waves are established in the Baltic. When the waves reach the narrow and shallow Neva Bay, they become much higher, ultimately breaching the Neva embankments.

The worst such flood occurred in November 19, 1824, when the water level rose 4.21 meters above normal. The playwright Alexander Griboyedov wrote, "The embankments of the various canals had disappeared and all the canals had united into one. Hundred-year-old trees in the Summer Garden were ripped from the ground and lying in rows, roots upward." When the waters receded 569 people were dead, with thousands more injured or made ill - more than 300 buildings had been washed away. The 1824 inundation is the setting for Alexander Pushkin's famous poem, The Bronze Horseman (1834). Other disastrous floods took place in 1777 and 1924. The most recent flood occurred on 18-October 19, 1998, when the water level rose to 2.2 meters.

For years, prominent scientists and statesmen of imperial Russia developed various plans for flood protection, and the Soviet Union implemented the idea. The flood of 1955 finally made it clear that Saint Petersburg needed a protection dam. Many options were considered before the Soviet government decided on a 25.4-kilometer complex of 11 dams, including a six-lane highway on the top.

In 1978 the project was officially approved and two years later construction began. However, work stopped for over 15 years due to lack of funds, and to environmental protests. In 2003 construction resumed and in 2005 it received a boost with the announcement of a new manager and a large increase in financial aid. It is believed that the President Vladimir Putin - a native of Saint Petersburg - was personally involved in finding a solution. Thanks to the pressure at federal level, the project is now due for completion in 2008.