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Breaking Barriers. © ILO/Naveed Akram.
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 IGO License. To view a copy of this license, visit creativecommons.org/licenses/by-nc-nd/3.0/igo/deed.en_US.
The above photo has been shot with the Samsung SMART CAMERA NX20, which has been provided by Samsung Electronics. Co., Ltd.
Continuing our tourist trip to Cairns on our last full day in Australia we visited the Great Barrier Reef. This shot was taken from a glass bottomed boat taking a tour over the coral. Obviously this was taken through glass so the quality isn't that great but hopefully you still get an impression of the coral and the seabed.
The Churchill Barriers are a series of four causeways in Orkney with a total length of 1.5 miles. They link the Mainland in the north to South Ronaldsay, via Burray, and the two smaller islands of Lamb Holm and Glimps Holm.
The barriers were built in the 1940s primarily as naval defences to protect the anchorage at Scapa Flow, but now serve as road links, carrying the A961 road from Kirkwall to Burwick.
On 14 October 1939, the Royal Navy battleship HMS Royal Oak was sunk at her moorings within the natural harbour of Scapa Flow by the German U-boat U-47. Shortly before midnight on 13 October U-47, under the command of Günther Prien, had entered Scapa Flow through Kirk Sound between Lamb Holm and the Orkney Mainland. Although the shallow eastern passages had been secured with measures including sunken block ships, booms and anti-submarine nets, Prien was able to navigate the U-47 around the obstructions at high tide. He launched a torpedo attack on the Royal Navy battleship while it was at anchor in Scapa Flow. The U-47 then escaped seaward using the same channel by navigating between the block ships.
In response, First Lord of the Admiralty Winston Churchill ordered the construction of several permanent barriers to prevent any further attacks. Work began in May 1940 and was completed by September 1944. The barriers were officially opened on 12 May 1945, four days after the end of World War II in Europe.
The contract for building the barriers was awarded to Balfour Beatty, although part of the southernmost barrier (between Burray and South Ronaldsay) was sub-contracted to William Tawse & Co. The first Resident Superintending Civil Engineer was E K Adamson, succeeded in 1942 by G Gordon Nicol.
Preparatory work on the site began in May 1940, while experiments on models for the design were undertaken at Whitworth Engineering Laboratories at the University of Manchester.
The bases of the barriers were built from gabions enclosing 250,000 tons of broken rock from quarries on Orkney. The gabions were dropped into place from overhead cableways into waters up to 59 feet deep. The bases were then covered with 66,000 locally cast concrete blocks in five-ton and ten-ton sizes. The five-ton blocks were laid on the core, and the ten-ton blocks were arranged on the sides in a random pattern to act as wave-breaks.
A project of this size required a substantial labour force, which peaked in 1943 at over 2,000.
Much of the labour was provided by over 1300 Italian prisoners of war who had been captured in the North African Campaign, and were transported to Orkney from early 1942 onwards. As the use of POW labour for war effort works is prohibited under the Geneva Conventions, the works were justified as "improvements to communications" to the southern Orkney Islands.
The prisoners were accommodated in three camps, 600 at Camp 60 on Little Holm and the remaining 700 at two camps on Burray. Those at Camp 60 built the ornate Italian Chapel which survives and has become a tourist attraction.
They had made a barrier of ice-blocks around the hole they had sawn up in the ice.
Knivsåsens stenbrott (Dalby stenbrott)
A car can be seen on the road on the Churchill Barrier. There is more Online Info about the Churchill Barriers at www.undiscoveredscotland.co.uk/eastmainland/churchill/
Their original purpose was to prevent any further U-Boat incursions into Scapa Flow during the Second World War.
Mike Rowe, from the television series "Dirty Jobs", was at the Stamford Hurricane Barrier in October 2006, for the barrier's yearly maintenance. The barrier normally sits flat on the ocean floor. It is only raised during storm surges to protect the harbor.
The main job is to identify anodes in need of repair and replace them. There are approximately 550 anodes that protect the metal gate from erosion. The zinc has an electrical charge that attracts the corrosion. They decide when to change the anodes by comparing a new anode to a used one. When the used anodes appear to have less than 50% left, they replace them.
The barrier is about four feet wide and goes down for six levels. Inside, it is filled with cubicles (about 17 across) with six anodes each. Each cubicle is covered with muck from the bottom of the harbor. The sediment and decay are hosed down to the next level. Fish, eels and other creatures can be found living in the sediment.
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The Thames Barrier prevents the floodplain of most of Greater London from being flooded by 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 approximately 3 km (1.9 mi) due east of 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.
Design and construction
The concept of the rotating gates was devised by (Reginald) Charles Draper. 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 taps on his gas cooker. The barrier was designed by Rendel, Palmer and Tritton for the Greater London Council and 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 the barrier. Work began at the barrier site in 1974 and construction, which had been undertaken by a Costain/Hollandsche Beton Maatschappij/Tarmac Construction consortium, was largely complete by 1982. The gates of the barrier were made by Cleveland Bridge UK Ltd at Dent's Wharf on the River Tees.
In addition to the barrier, the flood defences for 11 miles down river were raised and strengthened. The barrier was officially opened on 8 May 1984 by Queen Elizabeth II. 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 (570 yd) 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 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.[6] Four radial gates by the riverbanks, also about 30 metres (100 ft) wide, can be lowered. These gate openings, unlike the main six, are non-navigable.
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 weir indicate that water levels would exceed 4.87 metres (16.0 ft) 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.
During the barrier's entire history up to April 2019, there have been 184 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.[9] 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.
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, the barrier was damaged when the dredger MV Sand Kite, operating in thick fog, hit one of the Thames Barrier's piers. 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.
The annual full test closure in 2012 was scheduled for 3 June to coincide with the Thames pageant celebrating Queen Elizabeth II's Diamond Jubilee. Flood risk manager Andy Batchelor said the pageant gave the Environment Agency "a unique opportunity to test its design for a longer period than we would normally be able to", and that the more stable tidal conditions in central London that resulted would help the vessels taking part.
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 and then the National Rivers Authority until April 1996 when it passed to the Environment Agency.
Future
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. At the time of its construction, the barrier was expected to be used 2–3 times per year. It is now being used 6–7 times per year.
This defence level included long-term changes in sea and land levels as understood at that time (c. 1970). Despite global warming and a consequently greater predicted rate of sea level rise, recent analysis extended the working life of the barrier until around 2060–2070. 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 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 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 the Thames Hub integrated infrastructure vision. The barrier would incorporate hydropower turbines to generate renewable energy and include road and rail tunnels, providing connections from Essex to a major new hub airport on the Isle of Grain.
In January 2013, in a letter to The Times, a former member of the Thames Barrier Project Management Team, Dr Richard Bloore, stated that the flood barrier was not designed with increased storminess and sea level rises in mind, and called for a new barrier to be looked into immediately. The Environment Agency responded that it does not plan to replace the Thames Barrier before 2070, as the barrier was designed with an allowance for sea level rise of 8 mm per year until 2030, which has not been realised in the intervening years. The barrier is around halfway through its designed lifespan. The standard of protection it provides will gradually decline over time after 2030, from a 1 in 1000 year event. The Environment Agency are examining the Thames Barrier for its potential design life under climate change, with early indications being that subject to appropriate modification, the Thames Barrier will be capable of providing continued protection to London against rising sea levels until at least 2070.
In June 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 circa 60m.
Naturally, there is a strong barrier along both sides of the pier ~ safety first!!
Stay Safe and Healthy Everyone
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I went to the Thames Barrier for the first time on Saturday afternoon - it was a lovely bright and bracing winter's day, Joy was at the ballet with her mum and sister, and my geeky poring over maps suggested that the sun was going to set in just the right direction for this stretch of river (fellow geeks, check this site out www.gaisma.com/en/location/london.html).
Whacked on the polariser and waited. Actually, I took lots of photos, but my tele shots of different parts of the barrier just weren't that interesting. Unlike the sky, and the water...
Continuing our tourist trip to Cairns on our last full day in Australia we visited the Great Barrier Reef. This shot was taken from a glass bottomed boat taking a tour over the coral. Obviously this was taken through glass so the quality isn't that great but hopefully you still get an impression of the coral and the seabed.