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Churchill Barriers
Scapa Flow, Orkney Isles, Scotland, UK
Churchill Barriers
associated engineer
Sir Frederick Arthur Whitaker
date  May 1940 - May 1945
UK era  Modern  |  category  Coast Protection  |  reference  HY483009
ICE reference number  HEW 1984
photo  © and licensed for reuse under this
The four Churchill Barriers are solid road causeways that link Orkney’s mainland via the islets of Lamb Holm and Glimps Holm to Burray and South Ronaldsay. They were constructed during World War II to protect the Royal Navy’s fleet anchored in Scapa Flow, Orkney. Their construction cut off the tidal flow to the North Sea, changing the coastal regime.
The natural harbour of Scapa Flow, north of John O’Groats, was ideal as the wartime fleet anchorage for the Royal Navy in both world wars. However, the four main channels on the eastern side of Scapa Flow were known to be vulnerable to attack by enemy submarines and torpedoes.
In 1915, engineer William Halcrow (1883-1958, knighted 1944) was invited to consider building permanent barriers across these channels but in the event, sunken blockships and anti-submarine netting proved a more expedient solution. After the end of World War I in 1918, 74 German ships were interned in Scapa Flow and they were scuttled in June 1919 on the orders of their German commanding officer Rear Admiral Ludwig von Reuter (1869-1943).
Some of the original blockships were later removed or had been moved by the sea. Their defence inadequacies were exposed in October 1939 when a German U-Boat found a way round them in Kirk or Holm Sound, the deepest and fastest flowing of the channels. It torpedoed HMS Royal Oak, the last battleship to be built at Devonport Dockyard in Plymouth, and escaped by the same route. A total of 833 lives were lost, and the site is now an official war grave.
This event occurred only six weeks after the start of World War II (1939-45) and prompted the construction of permanent barriers across the four channels. The barrier scheme was authorised by First Lord of the Admiralty, later Prime Minister, Winston Churchill (1874-1965) after a personal visit to the site in March 1940 — hence the name.
The causeways were designed by the Admiralty's Civil Engineer-In-Chief Frederick Arthur Whitaker (1893-1968, knighted 1945) to absorb a through tidal current of 4-5 knots per hour. Whitaker supervised construction, which was carried out under the direction of H.B. Hurst, who was succeeded by C.K. Johnstone-Burt, Herbert Chatley (1871-1955) and J.A. Seath. Preparations on site commenced in May 1940, and during that summer limited experiments were conducted on models in the Whitworth Engineering Laboratories at the University of Manchester.
The widest and deepest channel is the northernmost, between East Mainland and Lamb Holm, where the foundations of Barrier No.1 were laid in fast-flowing tidal waters up to 18m deep. Each barrier has a core of rubble-filled gabion baskets flanked by 5.1 tonne concrete blocks below the water line. For Barrier Nos.1, 2 and 4 these are in turn overlaid by 10.2 tonne blocks, with the outer layer placed in random fashion to break the force of the waves. Barrier No.3 (Weddel Sound) is less exposed and has 5.1 tonne blocks throughout.
The four barriers total some 2.4km in length and contain about 254,000 tonnes of rubble overlaid by 66,000 concrete blocks. The rock was quarried locally and the blocks were fabricated in timber moulds at casting yards in St Mary’s (mainland) and on Burray. The gabions were dropped into place from aerial cableways. There were five of these, two over Kirk Sound — four were driven electrically and one was powered by steam.
The barriers did not rise above the waters until 1942-3. The scheme cost some £2m and was completed in September 1944. The official opening by First Lord of the Admiralty Albert Victor Alexander (1885-1965) was on 12th May 1945, four days after VE Day.
A relaxed interpretation of the Geneva Convention, describing the project as "improvements to communications” rather than war works, allowed the labour force to be augmented substantially by around 1,300 Italian prisoners of war from early 1942 onwards. At its peak in 1943, more than 2,000 people were at work on the project.
The sites of the accommodation camps, rubble quarries, concrete casting yards and the associated railways are still traceable. A chapel on Lamb Holm, built by the Italians from two Nissen huts and scraps of available materials, is now a popular visitor attraction.
Though built as defensive structures, the barriers were finished too late to feature in World War II but remain in use as causeways carrying the A961 road linking the islands. Their existence has altered the wave and current system in Scapa Flow, resulting in the development of sand dunes along the eastern side of the southern barrier (No.4) between Burray and South Ronaldsay. Over the years, concern has been raised about the safety of driving over the barriers in bad weather, particularly Barrier No.2 between Lamb Holm and Glimps Holm.
In October 2011, Orkney Islands Council bought the Churchill Barriers from the Ministry of Defence for a "nominal sum". The sale gives the council ownership of the road network and the seabed beneath the barriers. Discussions of potential options include proposals for a marine energy project harnessing tidal flows below the structures to generate renewable energy.
Resident engineer (1940-2): E.K. Adamson
Resident engineer (1942-5): G. Gordon Nicol
Contractor: Balfour Beatty & Co Ltd
Sub-contractor (part of barrier No.4): William Tawse & Co
Aerial cableways: John M. Henderson & Co Ltd
Research: ECPK
"60 Years On – The Churchill Barriers Re-Visited" by Geoffrey Stell
in Panel for Historical Engineering Works Newsletter, No.106, Institution of Civil Engineers, June 2005
reference sources   CEH SHI

Churchill Barriers