Editing Thames Barrier (section)

===Operations===
The barrier was originally designed to protect London against a very high flood level (with an estimated [[return period]] of one hundred years) up to the year 2030, after which the protection would decrease, while remaining within acceptable limits.<ref>{{cite web |url=http://www.environment-agency.gov.uk/homeandleisure/floods/105205.aspx |title=Managing flood water: The future |author=<!--No author named.--> |publisher=Environment Agency |url-status=dead |archive-url=http://webarchive.nationalarchives.gov.uk/20090606062958/http://www.environment-agency.gov.uk/homeandleisure/floods/105205.aspx |archive-date=6 June 2009 |access-date=25 November 2009 }}</ref> At the time of its construction, the barrier was expected to be used 2–3 times per year. By the mid-2000s it was being operated 6–7 times a year.<ref>{{cite report |author=World Heritage Centre |date=May 2007 |title=Climate Change and World Heritage |chapter-url=https://whc.unesco.org/en/series/22/ |publisher=[[UNESCO]] |chapter-format=PDF |location=Paris |chapter=Predicting and Managing the Impacts of Climate Change on World Heritage |page=29 |url-status=live |archive-url=https://web.archive.org/web/20200715032811/https://whc.unesco.org/en/series/22/ |archive-date=2020-07-15}}</ref> In the 2010s, the barrier was generally (as a median) closed twice a year but the average is still 6–7 due to the extreme of 50 times in 2013–14.

This defence level allowed for long-term changes in sea and land levels as understood at that time (c. 1970). From 1982 until 19 March 2007, the barrier was raised one hundred times to prevent flooding. It is also raised monthly for testing,<ref name="ThamesWeb2007">{{cite web |url=http://www.thamesweb.com/news_story.php?news_id=144 |title=Thames Barrier Clocks 100 Closures |author=<!--No author named.--> |date=19 March 2007 |website=ThamesWEB |publisher=Thames Estuary Partnership |url-status=unfit |archive-url=https://web.archive.org/web/20081223120826/http://www.thamesweb.com/news_story.php?news_id=144 |archive-date=2008-12-23}}</ref> with a full test closure over high tide once a year.<ref name="bbc-test-closure" />