Misplaced Pages

#829170

51-464: The Thames Barrier is a retractable barrier system built to protect the floodplain of most of Greater London from exceptionally high tides and storm surges moving up from the North Sea . It has been operational since 1982. When needed, it is closed (raised) during high tide; at low tide, it can be opened to restore the river's flow towards the sea. Built about 2 miles (3.2 kilometres) east of

102-488: A 1-in-1000-year event. The Environment Agency was examining the Thames Barrier for its potential design life under climate change, with early indications being that subject to appropriate modification, the Thames Barrier would be capable of providing continued protection to London against rising sea levels. A UK Environment Agency review in 2023 said that new climate models showed heightened risk of flooding, implying

153-551: 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 km) of land, put hospitals, power stations and

204-491: A need for raised defences upstream of the Thames Barrier by 2050, but that the Thames Barrier was expected to continue to operate until 2070. A decision on the best option for adapting to sea level rise to 2100 will be taken by 2040. As of 2024 concerns exist that climate change is occurring faster than previously expected. Flood barrier The Delta Works in the Netherlands is the largest flood protection project in

255-451: A new barrier to be looked into immediately. The Environment Agency responded that it did not plan to replace the Thames Barrier before 2070, as it was designed with an allowance for sea level rise of 8 mm (0.31 in) per year, which has not happened in the intervening years. At the time, the barrier was around halfway through its designed lifespan. The standard of protection it provides will gradually decline over time after 2030, from

306-749: A temporary barrier. A reinforced concrete wall is an example of a permanent barrier. Sandbags have traditionally been used as temporary flood barriers. Cofferdam A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out or drained. This pumping creates a dry working environment so that the work can be carried out safely. Cofferdams are commonly used for construction or repair of permanent dams, oil platforms, bridge piers, etc., built within water. They also form an integral part of naval architecture . These cofferdams are usually welded steel structures, with components consisting of sheet piles , wales , and cross braces . Such structures are usually dismantled after

357-403: A unit, or prefabricated panels can be joined during erection. When partial cofferdams are used, it may be necessary to compensate for hydrostatic pressure on the deck by shoring the decks. With both complete and partial cofferdams, there is usually a large free surface in the spaces being pumped. Sometimes this can be limited by dewatering one compartment at a time, or in groups, taking into account

408-578: A working model. The novel rotating cylinders were based on the design of the taps 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. 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

459-672: A year. Released in 2005, a study by four academics contained a proposal to supersede the Thames Barrier with a more ambitious 16 km (10 mi) long barrier across the Thames Estuary from Sheerness in Kent to Southend-on-Sea in Essex . In November 2011, a new Thames Barrier, further downstream at Lower Hope between East Tilbury in Essex and Cliffe in Kent, was proposed as part of

510-591: 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 nearby Fox Point Hurricane Barrier protects

561-470: Is a proposed regional flood barrier system that would protect the harbor and the New York – New Jersey metropolitan region. The Ike Dike is a proposed flood barrier that would protect Houston, Texas. Flood barriers may be placed temporarily or permanently around individual buildings or at building entrances to keep floodwaters from entering those buildings. A wall constructed of sandbags is an example of

SECTION 10

#1732765052830

612-578: 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. The Saint Petersburg Dam (officially called the Saint Petersburg Flood Prevention Facility Complex)

663-429: Is done on the fittings inside the ship. This is more common in naval vessels where a cofferdam may fit several vessels of a class. The cofferdam is also used on occasion in the shipbuilding and ship repair industry, when it is not practical to put a ship in drydock for repair work or modernization. An example of such an application is the lengthening of ships. In some cases a ship is actually cut in two while still in

714-488: Is no opening to the interior of the vessel, or the interior is pressurised in this area. The air space is at the pressure of the water surface at the bottom of the chamber. Open top cofferdams allow surface access to the work area below the waterline, and are at atmospheric pressure. Openings through the hull to the interior of the ship are possible. Portable cofferdams can be inflatable or frame and fabric cofferdams that can be reused. Inflatable cofferdams are stretched across

765-480: Is submerged, flooded spaces cannot be dewatered until all openings are sealed or the effective freeboard is extended above the high water level. One method of doing this is to build a temporary watertight extension of the entire hull of the ship, or the space to be dewatered, to the surface. This watertight extension is a cofferdam. Although they are temporary structures, cofferdams for this purpose have to be strongly built, adequately stiffened, and reinforced to withstand

816-530: 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 2007 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

867-866: The Isle of Dogs , its northern bank is in Silvertown in the London Borough of Newham and its southern bank is in the New Charlton area of the Royal Borough of Greenwich . Flooding in London has been a problem since Roman times. 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

918-554: The London Underground out of action and cause damage estimated in 1966 at £2 billion (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. 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

969-580: 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. As of May 2024, there have been 221 flood defence closures. The barrier was closed twice on 9 November 2007 after a storm surge in the North Sea which was compared to the one in 1953. The main danger of flooding from the surge was on the coast above

1020-470: The Thames Hub integrated infrastructure vision . The barrier would incorporate 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 . In 2019 architects Lifschutz Davidson Sandilands and marine engineers Beckett Rankine launched a proposal for a pedestrian and cycle bridge located next to

1071-620: The "more stable tidal conditions … in central London … will help the vessels taking part". 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 . The barrier

SECTION 20

#1732765052830

1122-501: 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. On 20 August 1989, hours after the Marchioness disaster , the barrier was closed against a spring tide for 16 hours "to assist the diving and salvage operations". The barrier has survived 15 boat collisions without serious damage. On 27 October 1997,

1173-642: 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 60 m (200 ft). In a January 2013 letter to The Times , a former member of the Thames Barrier Project Management Team, Dr Richard Bloore, stated that it was not designed with increased storminess and sea level rises in mind, and called for

1224-440: The adjacent structure. There are two common types of dry chambers used in underwater ship husbandry. Open bottom cofferdams allow divers direct access to the enclosed hull area, system, or opening. The flange sides of the chamber secure and seal against the hull, acting as an airtight boundary. Open bottom cofferdams are typically used as diver work space for rigging or welding and ventilation for welding or epoxy cure, where there

1275-609: The banks, the possibility and cost of erecting a structure across the Thames which could be closed in a surge should be urgently investigated". A number of designs were put forward, from a huge road viaduct with two 500 foot (150 m) sluice gates crossing the Thames at Crayfordness to flap gates lying on the river bed and floated up by compressed air . 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). In 1966, Sir Hermann Bondi

1326-402: 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

1377-405: 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

1428-570: 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 / Hollandsche Beton Maatschappij / Tarmac Construction consortium. 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 UK Ltd . Work began at

1479-441: The beam strength loads on the ship induced by the load distribution. Small cofferdams are used for pumping or to allow salvors access to spaces that are covered by water at some stage of the tide. They are usually prefabricated and fitted around minor openings. Diving work on cofferdams often involves clearing obstructions, fitting, and fastening, including underwater welding, and where necessary, caulking , bracing and shoring

1530-554: The case of Avro Lancaster ED603 , which was recovered from the IJsselmeer in 2023 using a cofferdam, allowing for close examination of the wreckage, as well as to locate and repatriate the remains of its crew. A 100-ton open caisson that was lowered more than a mile to the sea floor in attempts to stop the flow of oil in the Deepwater Horizon oil spill has been called a cofferdam. A cofferdam over 1 mile long

1581-650: The city of Providence, Rhode Island . The US Army Corps of Engineers also owns and operates the hurricane barrier at Stamford, CT. The MOSE Project is intended to protect the city of Venice , Italy , and the Venetian Lagoon from flooding. The River Foss, York, UK has a barrier to control the inflow of fast moving water from the River Ouse that may overspill its banks upstream the Foss and flood surrounding properties. The New York Harbor Storm-Surge Barrier

Thames Barrier - Misplaced Pages Continue

1632-607: The confluence of these waterways is the largest in the United States. It protects the city from the Gulf of Mexico from flooding the area. The new Seabrook floodgate prevents a storm surge from entering from Lake Pontchartrain. 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

1683-460: The construction work is completed. The origin of the word comes from coffer (originally from Latin cophinus meaning 'basket') and dam from Proto-Germanic * dammaz meaning 'barrier across a stream of water to obstruct its flow and raise its level'). For dam construction, two cofferdams are usually built, one upstream and one downstream of the proposed dam, after an alternative diversion tunnel or channel has been provided for

1734-401: The contents of one or both of the compartments. The cofferdam would be kept empty at all times and the ship may have sensors within it to warn if it has begun to fill with liquid. If two different cargoes that react dangerously with each other are carried on the same vessel, one or more cofferdams are usually required between the cargo spaces. When all or part of the main deck of a sunken ship

1785-433: The engineering contractors can carry out their works. After the construction project is complete the sheet piles can then be removed and the area behind them rewetted. A cofferdam is a space between two watertight bulkheads or decks within a ship. It is usually a void (empty) space intended to ensure that the contents of nearly adjacent tanks cannot leak directly from one to the other which would result in contamination of

1836-600: The flat side of the gate caused by abrasion. The vessel was refloated in mid-November 1997. The annual full test closure in 2012 was scheduled for 3 June to coincide with the 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

1887-400: The geography of a dam site, in some applications, a U-shaped cofferdam is used in the construction of one half of a dam. When complete, the cofferdam is removed and a similar one is created on the opposite side of the river for the construction of the dam's other half. Cofferdams are used in ship husbandry to allow dry access to underwater equipment and to close underwater openings while work

1938-442: The hydrostatic and other loads that they will have to withstand. Large cofferdams are normally restricted to harbor operations. Complete cofferdams cover most or all of the sunken vessel and are equivalent to extensions of the ship's sides to above the water surface. Partial cofferdams are constructed around moderate-sized openings or areas such as a cargo hatch or small deckhouse. They can often be prefabricated and installed as

1989-499: The openings are circular segments 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 40 millimetres (1.6 in) thick. The gates are filled with water when submerged and empty as they emerge from the river. The four large central gates are 20.1 metres (66 ft) high and weigh 3,700 tonnes each. Four radial gates by

2040-609: The piers to form the gate recesses, with access tunnels at the upstream and downstream ends. The gates of the barrier were fabricated in sections at Cleveland Bridge's Darlington works and assembled at Port Clarence on the River Tees . 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 ). The mechanical and hydraulic machinery

2091-414: The river banks, also about 30 metres (100 ft) wide, can be lowered. These gate openings, unlike the main six, are non-navigable. 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 16 feet (4.9 m) in central London. Though Teddington marks

Thames Barrier - Misplaced Pages Continue

2142-404: The river flow to bypass the foundation area of the dam. These cofferdams are typically a conventional embankment dam of both earth- and rock-fill, but concrete or some sheet piling also may be used. Usually, upon completion of the dam and associated structures, the downstream coffer is removed and the upstream coffer is flooded as the diversion is closed and the reservoir begins to fill. Depending on

2193-406: The ships sinking and becoming impossible to repair. Several types of structure performing this function can be distinguished, depending on how they are constructed and how they are used. In civil and costal engineering applications cofferdams are usually made from interlocking steel sheet piles which are driven deep into the bed of the water source in order to create a temporary dam behind which

2244-559: The water, and a new section of ship is floated in to lengthen the ship. The cutting of the hull is done inside a cofferdam attached directly to the hull of the ship; the cofferdam is then detached before the hull sections are floated apart. The cofferdam is later replaced while the hull sections are welded together again. As expensive as this may be to accomplish, the use of a drydock might be even more expensive. Cofferdams are also used in some marine salvage operations. Cofferdams have been used to recover aircraft from water as well, as in

2295-767: 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

2346-404: 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. The barrier protects central London against a storm surge , caused when

2397-499: 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. In addition to the barrier, the flood defences 18 kilometres (11 mi) down river were raised and strengthened. The barrier

2448-544: Was built to permit the construction of the Livingstone Channel in the Detroit River. See main article at Stony Island . The museum battleships USS Alabama (BB-60) and USS North Carolina (BB-55) have had cofferdams since 2003 and 2018, respectively. This saves much money compared to towing and dry docking them after the tow and this also provides additional security so there is a low chance of

2499-408: 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, with a full test closure over high tide once

2550-567: Was officially opened on 8 May 1984 by Queen Elizabeth II . The barrier cost £461 million (£1.49 billion now). Total construction cost was around £534 million (£1.6 billion at 2016 prices) with an additional £100 million for river defences. Built across a 520-metre (1,710 ft) wide stretch of the river, the barrier divides the river into four 61-metre (200 ft) and two approximately 30-metre (100 ft) navigable spans. There are also four smaller non-navigable channels between nine concrete piers and two abutments. The flood gates across

2601-408: 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. 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. In the 2010s, the barrier

SECTION 50

#1732765052830
#829170