A sea barrier (also known as a storm surge barrier) is a structure at the mouth of a river or inlet that can be closed against coastal storm surge or high tides to help prevent flooding.
Sea barriers help protect coastal cities from flooding caused by storm surge or high tide. Modern versions feature moveable sea gates, which stay open most of time to accommodate tidal action, ship navigation, marine life and estuary ecosystems. The gates close during storms and high-water events to protect against waves and prevent surges from moving up inlets, rivers and estuaries to cause flooding.
In the Netherlands, Delta Works is a series of 13 sea barriers and dams that defend against storms on the North Sea. Other well-known works include the Thames Barrier (London), Eider Barrage (Tonning, Germany), St. Petersburg Dam, MOSE project (Venice) and Marina Barrage (Singapore). In the United States, storm surge barriers include those in New Orleans, New Bedford, and Providence.
The Lower Mainland has not used sea barriers of the kind installed in some international port cities.
In the City of Surrey, the Nicomekl and Serpentine Rivers are controlled by “sea dams” that were constructed in the early 1900s. Regulated as dikes under the Dike Maintenance Act, these flood control works span a cross-section of both rivers to minimize the flooding that could result during high tide and coastal storms. They also support agricultural access to freshwater that would otherwise be unsuitable due to natural brackish conditions. Other municipalities in the Lower Mainland are considering the use of sea barriers for flood management.