Editing Thames Barrier (section)

==History==
===Background===
Flooding in London has been a problem since [[Roman Britain|Roman]] times.<ref name=":1">{{cite journal |last=Kendrick |first=Mary |author-link=Mary Kendrick |date=1988 |title=The Thames Barrier |journal=Landscape and Urban Planning |volume=16 |issue=1–2 |pages=57–68 |doi=10.1016/0169-2046(88)90034-5|bibcode=1988LUrbP..16...57K }}</ref> In 1954, the Waverley Committee, established to investigate the serious [[North Sea flood of 1953]] which affected parts of the [[Thames Estuary]] and parts of London, recommended that "as an alternative to raising the banks, the possibility and cost of erecting a structure across the Thames which could be closed in a surge should be urgently investigated".<ref>
{{cite hansard |title=Coastal Flooding (Committee's Report) |url=https://api.parliament.uk/historic-hansard/written-answers/1954/jun/03/coastal-flooding-committees-report |house=House of Commons |date=3 June 1954 |volume=528 |column_start=104 |column_end=5W |speaker=[[David Maxwell Fyfe, 1st Earl of Kilmuir|D. Maxwell Fyfe]] |position=[[Home Secretary]] |hansard=Written Answers (Hansard)}}</ref> A number of designs were put forward, from a huge road viaduct with two 500 foot (150 m) [[sluice gate]]s crossing the Thames at [[Crayford]]ness to flap gates lying on the [[river bed]] and floated up by [[compressed air]].<ref name=":0">{{cite book |last1=Gilbert |first1=Stuart |last2=Horner |first2=Ray |title=The Thames Barrier |year=1984 |publisher=T. Telford |location=London |isbn=978-0-7277-0182-4 |oclc=11594001}}</ref>{{page needed|date=March 2021}} By 1965, when the [[Greater London Council]] (GLC) took over responsibility, two major schemes were under consideration, costed at £24 million and £41 million respectively (£500 million and £800 million at 2020 prices).<ref name=":0"/>{{page needed|date=March 2021}}

In 1966, Sir [[Hermann Bondi]] was asked to take an independent view of the situation. He considered the estimated construction costs and the probability of a flood and of damage if the barrier was not built. He strongly recommended that a barrier should be built in order to avoid the catastrophe of flooding central London, and a site was agreed at Woolwich.<ref name=":0" />{{page needed|date=March 2021}}

The barrier protects central London against a [[storm surge]], caused when a deep depression forms to the north of Scotland and progresses across the [[North Sea]] and south-easterly towards southern Scandinavia. When such a surge coincides with a high [[spring tide]], the high winds associated with the depression can funnel the water up the [[Thames Estuary]] and cause surges of up to 3.5 metres (11.6 feet). The planners assessed that in the absence of a barrier, such a surge could inundate 45 square miles (117&nbsp;km<sup>2</sup>) of land, put hospitals, power stations and the [[London Underground]] out of action and cause damage estimated in 1966 at £2 billion<ref>''The Thames Barrier: The Background and Basic Engineering Requirements''. D Ayres Director of Public Health Engineering, GLC. 1983. Paper presented to a meeting of the Institution of Mechanical Engineers, 8th June 1983</ref> (about £50 billion at 2020 prices). The barrier was designed to provide a flood defence capable of resisting a once in 1000 year surge tide at a base date of 2030.

===Design and construction===
[[File:Thames Barrier - simple operation diagram.png|thumb|right|upright=1.2|Diagram showing how the gates work, though the barrier actually rises further than this to allow water to "underspill" under the barrier in a controlled fashion]]

The concept of the rising sector gates was devised by (Reginald) Charles Drapeer. In 1969, from his parents' house in Pellatt Grove, [[Wood Green]], London, he constructed a working model. The novel rotating cylinders were based on the design of the [[Tap (valve)|tap]]s on his [[gas cooker]]. The barrier was designed by Rendel, Palmer and Tritton for the [[Greater London Council]] and the concept tested at the [[Hydraulics Research Station]], Wallingford.<ref name=":1" /> The site at New Charlton was chosen because of the relative straightness of the banks, and because the underlying river [[chalk]] was strong enough to support the barrier.

The Thames Barrier and Flood Prevention Act, authorising construction, was passed in 1972. In 1974, the GLC placed the two major construction contracts. Civil construction was undertaken by a [[Costain Group|Costain]]/[[Royal BAM Group|Hollandsche Beton Maatschappij]]/[[Tarmac Group|Tarmac Construction]] consortium.<ref name=":0" />{{page needed|date=March 2021}} A separate contract for the gates and operating machinery was placed with the Davy Cleveland Barrier Consortium, formed by Davy McKee Ltd of Sheffield and [[Cleveland Bridge & Engineering Company|Cleveland Bridge UK Ltd]].<ref>{{cite web |url=https://www.gracesguide.co.uk/Davy_Cleveland_Barrier_Consortium |title=Davy Cleveland Barrier Consortium |author=<!--No author named.--> |date=30 July 2019 |website=Grace's Guide |url-status=live |archive-url=https://web.archive.org/web/20201124201649/https://www.gracesguide.co.uk/Davy_Cleveland_Barrier_Consortium |archive-date=2020-11-24}}</ref><ref name=":0" />{{page needed|date=March 2021}}

Work began at the barrier site in 1974 and progressed in two phases. The southern piers (9 to 6) were built first, with river traffic diverted to the north side, then traffic routed through the completed southern spans whilst the north side piers (1 to 5) were built. During construction of the piers, precast concrete sills were built in a [[cofferdam]] on the north side of the river and floated out and sunk between the piers to form the gate recesses, with access tunnels at the upstream and downstream ends.<ref>{{cite web |url=http://www.environment-agency.gov.uk/homeandleisure/floods/38355.aspx |title=Engineers and main contractors for the building of the Thames Barrier |author=<!--No author named.--> |publisher=Environment Agency |url-status=dead |archive-url=http://webarchive.nationalarchives.gov.uk/20090205134525/http://www.environment-agency.gov.uk/homeandleisure/floods/38355.aspx |archive-date=5 February 2009 |access-date=13 March 2021 }}</ref>

The gates of the barrier were fabricated in sections at Cleveland Bridge's [[Darlington]] works and assembled at [[Port Clarence]] on the [[River Tees]].<ref>{{cite journal |last=Horner |first=R. W. |date=July 1979 |title=The Thames Barrier Project |journal=The Geographical Journal |volume=145 |issue=2 |pages=242–253 |doi=10.2307/634390 |jstor=634390|bibcode=1979GeogJ.145..242H }}</ref>{{rp|251}} The gates, gate arms and rocking beams were transported from the Tees to the Thames by barge and lifted into position by two very large floating cranes operated by Neptun of Hamburg (now part of [[Smit International]]).<ref>Manufacture and Installation of the Barrier Gates and Operating Machinery – P F Harvey, Davy Cleveland Barrier Consortium – Institution of Mechanical Engineers – Paper presented at a meeting on 8th June 1983.</ref> The mechanical and hydraulic machinery was built by Davy Loewy, Henry Berry and Vickers and trial assembled in Davy's Darnall works. Delays to the civil works required changes to the construction and installation sequence, but commissioning was relatively uneventful and the first trial operation of all the gates together was carried out on 31 October 1982.<ref>{{cite news |last=Clayton |first=Hugh |date=4 November 1982 |title=All 10 gates being raised at the Thames barrier |url=https://www.thetimes.com/tto/archive/frame/article/1982-11-04/3/1.html |work=The Times |page=3 |access-date=2021-03-12}}</ref>

In addition to the barrier, the flood defences {{convert|11|mi|order=flip}} down river were raised and strengthened. The barrier was officially opened on 8 May 1984 by Queen [[Elizabeth II]].<ref name=Guardian>{{cite news |title=Better way to turn the tide |newspaper=[[The Guardian]] |date=9 May 1984 |page=2 |url=https://www.newspapers.com/image/259609689/}} {{subscription required|via=Newspapers.com}}</ref> The barrier cost £{{Format price|461000000}} (£{{Format price|{{Inflation|UK-GDP|461000000|1984}}}} now).<ref name=Guardian />{{Inflation/fn|UK-GDP}} Total construction cost was around £535 million (£2.4 billion at 2024 prices)<ref name="EnvironmentAgencyMay2024">{{Cite web |url=https://www.gov.uk/government/news/the-thames-barrier-protecting-london-and-the-thames-estuary-for-40-years |title=The Thames Barrier – protecting London and the Thames Estuary for 40 years |author1=<!--No personal author name given.--> |date=2024-05-08 |department=Environment Agency |website=[[GOV.UK]] |type=Press release |url-status=live |archive-url=https://web.archive.org/web/20240508014811/https://www.gov.uk/government/news/the-thames-barrier-protecting-london-and-the-thames-estuary-for-40-years |archive-date=2024-05-08}}</ref> with an additional £100 million for river defences.{{citation needed|date=December 2024|reason=Additional river defences not mentioned in Environment Agency press release}}

Built across a {{convert|520|m|ft|adj=on}} wide stretch of the river, the barrier divides the river into four {{convert|61|m|ft|adj=on}} and two approximately 30-metre (100&nbsp;ft) navigable spans. There are also four smaller non-navigable channels between nine concrete piers and two abutments. The flood gates across the openings are [[circular segment]]s in cross section, and they operate by rotating, raised to allow "underspill" to allow operators to control upstream levels and a complete 180 degree rotation for maintenance. All the gates are hollow and made of steel up to {{convert|40|mm|in}} thick. The gates are filled with water when submerged and empty as they emerge from the river. The four large central gates are {{convert|20.1|m|ft}} high and weigh 3,700 [[tonne]]s each.<ref>{{cite web |url=http://www.environment-agency.gov.uk/static/documents/Leisure/Thames_Barrier_2010_project_pack.pdf |title=The Thames Barrier Project Pack 2010 |publisher=Environment Agency |url-status=dead |archive-url=http://webarchive.nationalarchives.gov.uk/20101216014218/http://www.environment-agency.gov.uk/static/documents/Leisure/Thames_Barrier_2010_project_pack.pdf |archive-date=16 December 2010 |access-date=18 October 2011 }}</ref> Four radial gates by the river banks, also about 30 metres (100&nbsp;ft) wide, can be lowered. These gate openings, unlike the main six, are non-navigable.{{citation needed|date=November 2021}}

===Predictions for operation===
A Thames Barrier flood defence closure is triggered when a combination of high tides forecast in the North Sea and high river flows at the [[tidal limit]] at [[Teddington Lock]] indicate that water levels would exceed {{convert|16|ft|m}} in central London. Though Teddington marks the [[Normal Tidal Limit]], in periods of very high fluvial flow the tidal influence can be seen as far upstream as [[East Molesey]] on the Thames.<ref>{{cite news |last=de Castella |first=Tom |url=https://www.bbc.com/news/magazine-26133660 |title=How does the Thames Barrier stop London flooding? |work=BBC News |date=11 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20200608223429/https://www.bbc.com/news/magazine-26133660 |archive-date=2020-06-08}}</ref>

{{wide image|Thames Barrier, London, England - Feb 2010.jpg|900px|The barrier from [[Silvertown]] on the north bank of the river during normal operation, looking across to [[New Charlton]]}}
{{clear}}

===Barrier closures and incidents===
{| class="wikitable sortable" style="text-align:right; float:right; margin:0 0 1em 1em;"
|+ Closures per season (Sept–May) and&nbsp;flooding source 
|-
! Season 
! Tidal
! Combined <br> tidal/ <br> fluvial
! Total<br><ref name="GOV.UK-Guidance">{{cite web |url=https://www.gov.uk/guidance/the-thames-barrier |title=The Thames Barrier |author1=<!--No personal author name given.--> |department=Environment Agency |website=GOV.UK |date=25 April 2014 |orig-date=last updated 5 September 2024 |url-status=live |archive-url=https://web.archive.org/web/20241113154040/https://www.gov.uk/guidance/the-thames-barrier |archive-date=2024-11-13}}</ref>
|-
|1982–83
|1
|0
|1
|-
|1983–84
|0
|0
|0
|-
|1984–85
|0
|0
|0
|-
|1985–86
|0
|1
|1
|-
|1986–87
|1
|0
|1
|-
|1987–88
|0
|0
|0
|-
|1988–89
|1
|0
|1
|-
|1989–90
|1
|3
|4
|-
|1990–91
|2
|0
|2
|-
|1991–92
|0
|0
|0
|-
|1992–93
|4
|0
|4
|-
|1993–94
|3
|4
|7
|-
|1994–95
|2
|2
|4
|-
|1995–96
|4
|0
|4
|-
|1996–97
|1
|0
|1
|-
|1997–98
|1
|0
|1
|-
|1998–99
|2
|0
|2
|-
|1999–00
|3
|3
|6
|-
|2000–01
|16
|8
|24
|-
|2001–02
|3
|1
|4
|-
|2002–03
|8
|12
|20
|-
|2003–04
|1
|0
|1
|-
|2004–05
|4
|0
|4
|-
|2005–06
|3
|0
|3
|-
|2006–07
|8
|0
|8
|-
|2007–08
|6
|0
|6
|-
|2008–09
|1
|4
|5
|-
|2009–10
|2
|3
|5
|-
|2010–11
|0
|0
|0
|-
|2011–12
|0
|0
|0
|-
|2012–13
|0
|5
|5
|-
|2013–14
|9
|41
|50
|-
|2014–15
|1
|0
|1
|-
|2015–16
|1
|0
|1
|-
|2016–17
|2
|0
|2
|-
|2017–18
|3
|0
|3
|-
|2018–19
|3
|0
|3
|-
|2019–20
|9
|0
|9
|-
|2020–21
|2
|4
|6
|-
|2021–22
|7
|0
|7
|-
|2022–23
|2
|0
|2
|-
|2023–24
|2
|11
|13
|-
|2024–25
|0
|0
|0
|-
! Totals
|'''119'''
|'''102'''
|'''221'''
|}

{{As of|2024|May}}, there have been 221 flood defence closures.<ref name="GOV.UK-Guidance" /> The barrier was closed twice on 9 November 2007 after a [[North Sea flood of 2007|storm surge]] in the North Sea which was compared to the one in 1953.<ref>{{cite news |author=<!--No author named.--> |date=9 November 2007 |title=North Sea flood tide fears recede |url=http://news.bbc.co.uk/2/hi/uk_news/england/7086175.stm |work=BBC News |url-status=live |archive-url=https://web.archive.org/web/20200630014628/http://news.bbc.co.uk/2/hi/uk_news/england/7086175.stm |archive-date=2020-06-30}}</ref> The main danger of flooding from the surge was on the coast above the Thames Barrier, where evacuations took place, but the winds abated a little and, at the Thames Barrier, the 9 November 2007 storm surge did not completely coincide with high tide.<ref>{{cite web |url=http://www.pol.ac.uk/home/news/2007-11stormsurge.html |title=Surge of 9 November 2007-11-09 |author=<!--No author named.--> |date=9 November 2007 |department=[[Proudman Oceanographic Laboratory]] |publisher=[[Natural Environment Research Council]] |url-status=unfit |archive-url=https://web.archive.org/web/20120221223805/http://www.pol.ac.uk/home/news/2007-11stormsurge.html |archive-date=2012-02-21}}</ref>

On 20 August 1989, hours after the [[Marchioness disaster|''Marchioness'' disaster]], the barrier was closed against a spring tide for 16 hours "to assist the diving and salvage operations".<ref name="maib-marchioness-3">{{cite report |url=https://www.gov.uk/maib-reports/collision-between-aggregates-dredger-bowbelle-and-passenger-vessel-marchioness-on-the-river-thames-england-resulting-in-marchioness-sinking-with-loss-of-51-lives |title=Report of the Chief Inspector of Marine Accidents into the collision between the passenger launch ''Marchioness'' and MV ''Bowbelle'' with loss of life on the River Thames on 20 August 1989 |date=5 June 1990 |publisher=[[Department of Transport]], [[Marine Accident Investigation Branch]] |section=Part III |format=PDF |access-date=12 March 2021}}</ref>

The barrier has survived 15 boat collisions without serious damage.<ref name=telegraph-20140218>{{cite news |last=Hanlon |first=Michael |author-link=Michael Hanlon |url=https://www.telegraph.co.uk/news/weather/10646439/The-Thames-Barrier-has-saved-London-but-is-it-time-for-TB2.html |url-access=subscription |title=The Thames Barrier has saved London – but is it time for TB2? |newspaper=The Telegraph |location=London |date=18 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20161112091127/http://www.telegraph.co.uk/news/weather/10646439/The-Thames-Barrier-has-saved-London-but-is-it-time-for-TB2.html |archive-date=2016-11-12}}</ref>

On 27 October 1997, the barrier was damaged when the [[dredger]] MV ''Sand Kite'' hit one of the piers in thick fog. As the ship started to sink she dumped her 3,300-tonne load of aggregate, finally sinking by the bow on top of one of the barrier's gates, where she lay for several days. Initially the gate could not be closed as it was covered in a thick layer of gravel. A longer-term problem was the premature loss of paint on the flat side of the gate caused by abrasion. The vessel was refloated in mid-November 1997.<ref name="maib-sand-kite">{{cite report |url=https://www.gov.uk/maib-reports/contact-made-by-dredger-sand-carrier-sand-kite-with-the-thames-flood-barrier-river-thames-england-resulting-in-flooding-and-partial-sinking-of-vessel |title=Report of the Inspector's Inquiry into the collision of MV ''Sand Kite'' with the Thames Flood Barrier on 27 October 1997 |date=April 1999 |publisher=[[Department of the Environment, Transport and the Regions]], [[Marine Accident Investigation Branch]] |format=PDF |access-date=12 March 2021}}</ref>

The annual full test closure in 2012 was scheduled for 3 June to coincide with the [[Thames Diamond Jubilee Pageant|Thames pageant]] celebrating the [[Diamond Jubilee of Elizabeth II]]. [[Environment Agency]] said the pageant provided "a unique opportunity to test its design for a longer period than we would normally be able to", and performance under conditions of "a higher water level upstream than downstream"; also that the "more stable tidal conditions … in central London … will help the vessels taking part".<ref name="bbc-test-closure">{{cite news |title=Thames Barrier test closure to be on Jubilee pageant day |date=6 March 2012 |work=BBC News |url=https://www.bbc.com/news/uk-england-london-17266139 |url-status=live |archive-url=https://web.archive.org/web/20210313032146/https://www.bbc.com/news/uk-england-london-17266139 |archive-date=2021-03-13}}</ref>

===Ownership and operating authority===
The barrier was originally commissioned by the [[Greater London Council]] under the guidance of Ray Horner. After the 1986 abolition of the GLC it was operated successively by [[Thames Water Authority]] (dissolved 1989) and then the [[National Rivers Authority]] until April 1996 when it passed to the [[Environment Agency]].

===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" />

===Past proposals for development===
Released in 2005, a study by four academics contained a proposal to supersede the Thames Barrier with a more ambitious 16&nbsp;km (10&nbsp;mi) long barrier across the Thames Estuary from [[Sheerness]] in [[Kent]] to [[Southend-on-Sea]] in [[Essex]].<ref>{{cite news |last=Leake |first=Jonathan |date=9 January 2005 |title=Ten mile barrier to stop London flood |url=https://www.thetimes.com/uk/science/article/ten-mile-barrier-to-stop-london-flood-svs2r99x8xq |url-access=subscription |work=The Sunday Times |url-status=live |archive-url=https://web.archive.org/web/20210312210221/https://www.thetimes.co.uk/article/ten-mile-barrier-to-stop-london-flood-svs2r99x8xq |archive-date=2021-03-12}}</ref>

In November 2011, a new Thames Barrier, further downstream at Lower Hope between [[East Tilbury]] in Essex and [[Cliffe, Kent|Cliffe]] in Kent, was proposed as part of the [[Thames Hub integrated infrastructure vision]]. The barrier would incorporate [[Tidal power|turbines to generate renewable energy]] and include road and rail tunnels, providing connections from Essex to a major new [[Thames Estuary Airport]] on the [[Isle of Grain]].<ref>{{cite web |title=Thames Hub: An Integrated Vision for Britain |publisher=Foster+Partners, Halcrow, Volterra |url= http://www.halcrow.com/Thames-Hub/PDF/Thames_Hub_vision.pdf |archive-url=https://web.archive.org/web/20111110074451/http://www.halcrow.com/Thames-Hub/PDF/Thames_Hub_vision.pdf |url-status=dead |archive-date=10 November 2011}}</ref>

In 2019 architects [[Lifschutz Davidson Sandilands]] and marine engineers Beckett Rankine launched a proposal for a pedestrian and cycle bridge located next to the Thames Barrier; the scheme, called the Thames Barrier Bridge, was promoted as the only location in east London where a low-level opening bridge across the Thames could have relatively moderate opening spans of about {{cvt|60|m}}.<ref>{{cite magazine |last=Horgan |first=Rob |date=3 June 2019 |title=Thames Barrier Bridge proposal revealed |url=https://www.newcivilengineer.com/latest/thames-barrier-bridge-proposal-revealed-03-06-2019/ |url-access=limited |magazine=New Civil Engineer |url-status=live |archive-url=https://web.archive.org/web/20210129121044/https://www.newcivilengineer.com/latest/thames-barrier-bridge-proposal-revealed-03-06-2019/ |archive-date=2021-01-29}}</ref><ref>{{cite news |last=Waite |first=Richard |date=3 June 2019 |title=Lifschutz Davidson Sandilands reveals Thames Barrier bridge plans |url=https://www.architectsjournal.co.uk/news/lifschutz-davidson-sandilands-reveals-thames-barrier-bridge-plans |work=Architects' Journal |url-status=live |archive-url=https://web.archive.org/web/20210313000533/https://www.architectsjournal.co.uk/news/lifschutz-davidson-sandilands-reveals-thames-barrier-bridge-plans |archive-date=2021-03-13}}</ref><ref>{{cite web |title=Thames Barrier Bridge |publisher=Lifschutz Davidson Sandilands, Beckett Rankine |url= https://www.thamesbarrierbridge.com/ |access-date=11 June 2019}}</ref>