A flood barrier, surge barrier or storm surge barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, levees (also known as dikes), and other constructions and natural geographical features.
Surge barriers allow water to pass under normal circumstances but, when a (storm) surge is expected, the barrier can be closed. The means of closing can consist of various forms of gates.
Flood barriers around the world
The Delta Works in the Netherlands is the largest flood protection project in the world. This project consists of a number of surge barriers, the Oosterscheldekering being the largest surge barrier in the world, 9 kilometres (5.6 mi) long. Other examples include the Maeslantkering, Haringvlietdam and the Hartelkering.
The Thames Barrier is the world's second largest movable flood barrier (after the Oosterscheldekering and the Haringvlietdam) and is located downstream of central London. Its purpose is to prevent London from being flooded by exceptionally high tides and storm surges moving up from the North Sea. It needs to be raised (closed) only during high tide; at ebb tide it can be lowered to release the water that backs up behind it.
In 2009 the United States Army Corps of Engineers started construction of an ambitious project that aimed to prevent storm surges from flooding the city by 2011. The IHNC Lake Borgne Surge Barrier on the confluence of these waterways is the largest in the United States. The new Seabrook floodgate prevents a storm surge from entering from Lake Ponchartrain. The GIWW West Closure Complex closes the Gulf Intracoastal Waterway to protect the west side of the city. This complex is unique in that it contains the world's largest pumping station, necessary to pump out rainwater that is discharged in the protected side of the canal during a hurricane.
The Eider Barrage is located at the mouth of the river Eider near Tönning on Germany’s North Sea coast. Its main purpose is protection from storm surges by the North Seas. It is Germany’s largest coastal protection structure.
St. Petersburg Dam
The Saint Petersburg Dam (officially called the Saint Petersburg Flood Prevention Facility Complex) is a 16 km (9.9 mi) barrier separating the Gulf of Finland from Neva Bay to protect the city of Saint Petersburg, Russia from coastal flooding. The Soviet Union started construction of the barrier in 1978 and it was completed and made operational in 2011.
The New Bedford Harbor Hurricane Barrier protects the city of New Bedford, Massachusetts, with a mostly immovable barrier of stone and fill. It has three land and one marine door for access in calm seas.
The US Army Corps of Engineers also owns and operates the hurricane barrier at Stamford, CT.