The Thames Barrier is the world's second-largest movable flood barrier (after the Oosterscheldekering in the Netherlands) and is located downstream of central London, United Kingdom. Operational since 1982, its purpose is to prevent the floodplain of all but the easternmost boroughs of Greater London from being flooded by exceptionally high tides and storm surges moving up from the North Sea. When needed, it is closed (raised) during high tide; at low tide it can be opened to enhance the river's flow towards the sea.
