Author(s): Rosa R. Mikhailenko
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Keywords: Hydraulic system; Flood warning system; Manoeuvring; Damage assessment
Abstract: St. Petersburg is located in the end point of the largest in Europe water system, which has a strategic value for the economic and social city development. The low-lying area of the delta of the Neva River is open to floods, and their frequency is increasing. The city has suffered more than three hundred floods since its foundation in 1703. The most specific features of St. Petersburg are abundance of water and lots of historic monuments of great value. St. Petersburg is often called “Venice of the North” and, like Venice, it has a role of world on the list of UNESCO. St. Petersburg Flood Protection Barrier (FPB), designed for 100 years of defence of the city from floods, is in the completion stage now. Nowadays it is important to develop a reliable system of multifunctional use of the Barrier to make it nature-friendly, not conflicting with the environment and use the FPB as a part of St. Petersburg integrated water management system. The FPB across Neva Bay at some 20-25 km from the city is a complicated hydraulic system, which consists of more than 30 constructions including 6 large sluice complexes, 2 wide navigation openings equipped with steel gates, each controlled separately, 11 dams, 7 bridges, a tunnel, etc. In normal situations the gates will be fully open to allow the free exchange of water. That is why most of the impacts of the completed Barrier will be negligible, but some changes in the environment after completion of the FPB cannot be excluded and have to be taken into account together with such considerable impacts on ecological state of Neva Bay and the Gulf of Finland, such as waste water and industrial discharges, oil pollution, etc. The changes in water quality as a result of the Barrier construction are minimal. The main functions of the Barrier are to protect St. Petersburg against catastrophic floods and improve ecological condition in Neva Bay and the Eastern part of the Gulf of Finland by means of water flow management using water gates manoeuvring. The Barrier can only adequately fulfil its task in combination with a reliable flood warning and risk assessment system. The main function of the system is to predict the flood threat early enough to close the flood gates before the flood wave arrives in St. Petersburg, and to make detailed predictions of hydraulic conditions for operation of the gates. This will increase the safety of navigation and reduce the risk of a collision in the navigation opening, which may damage the structure or block the gates. The Geographic Information System (GIS) for flood warning and economic and ecological damage assessment evaluates possible risks. The flood gates in the C-1 opening, the main of the 2 navigation sluices, are rather sensitive to high speed of water level rise and to high waves, the forecast system will help to determine the moment when these gates have to start closing. It will also help to optimise the timing of closing the sluices to keep the water levels in Neva Bay low enough not to flood the city.
Year: 2007