Mulberry harbour
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A Mulberry harbour was a type of temporary harbour developed in World War II to offload cargo on the beaches during the Allied invasion of Normandy.
The Mulberry harbours were two prefabricated or artificial military harbours, which were taken across the English Channel from Britain with the invading army in sections and assembled off the coast of Normandy as part of the D-Day invasion of France.
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[edit] Background
The Dieppe Raid of 1942 had shown that the Allies could not rely on being able to penetrate the Atlantic Wall to capture a port on the north French coast, thus the Mulberries were created to provide the port facilities necessary to offload the thousands of men and vehicles, and tons of supplies necessary to sustain Operation Overlord and the Battle of Normandy. The harbours were made up of all the elements one would expect of any harbour: breakwater, piers, roadways etc.
[edit] Development
The actual proposer of the idea of the Mulberry Harbour is disputed, but among those who are known to have proposed something along these lines is Hugh Iorys Hughes, a Welsh civil engineer who submitted initial plans on the idea to the War Office, Professor J. D. Bernal, and Vice-Admiral John Hughes-Hallett.
At a meeting following the Dieppe Raid, Hughes-Hallett declared that if a port could not be captured, then one should be taken across the Channel. This was met with derision at the time, but in a subsequent meeting with Churchill, the Prime Minister declared he had surmised a similar scenario using some Danish Islands and sinking old ships for a bridgehead for an invasion in World War I. The concept of Mulberry Harbours began to take shape when Hughes-Hallett moved to be Naval Chief of Staff to the Overlord planners.
A trial of the three eventual competing designs was set up, with tests of deployment including floating the elements, in Solway Firth, Scotland. The designs were by Hugh Iorys Hughes who developed his 'Hippo' piers and 'Crocodile' bridge units on the Conwy Morfa, using 1000 men to build the trial version; the Hamilton 'Swiss Roll' which consisted of a floating roadway; and a system of flexible bridging units supported on floating pontoons designed by Allan H Beckett. The tests revealed various issues (the 'Swiss Roll' would only take a maximum of a 7 ton truck in the Atlantic swell). However the final choice of design was determined by a storm during which the 'Swiss Roll' was washed away and the 'Hippos' were undermined; Beckett's floating roadway (subsequently codenamed Whale) survived undamaged. Beckett's design was adopted and manufactured under the management of J. D. Bernal and Brigadier Bruce White, under the orders of Sir Winston Churchill.
The proposed harbours called for many huge caissons of various sorts to build breakwaters and piers and connecting structures to provide the roadways. The caissons were built at a number of locations, mainly existing ship building facilities or large beaches like Conwy Morfa around the British coast. The works were let out to commercial construction firms including Robert McAlpine, Peter Lind & Company & Balfour Beatty who all still operate today. On completion they were towed across the English Channel to the Normandy coast at only 5 mph (8 km/h). The Mulberry Harbours cost more money to build than the Eurostar Channel Tunnel.
[edit] Deployment
By June 9, just 3 days after D-Day, two harbours codenamed Mulberry 'A' and 'B' were constructed at Omaha Beach and Arromanches, respectively. However, a large storm on June 19 destroyed the American harbour at Omaha, leaving only the British harbour which came to be known as Port Winston at Arromanches. While the harbour at Omaha was destroyed sooner than expected (due to it not being securely anchored to the sea bed), Port Winston saw heavy use for 8 months—despite being designed to last only 3 months. In the 100 days after D-Day, it was used to land over 2.5 million men, 500,000 vehicles, and 4 million tonnes of supplies providing much needed reinforcements in France.
A complete Mulberry harbour was constructed out of 600,000 tons of concrete between 33 jetties, and had 10 miles (15 km) of floating roadways to land men and vehicles on the beach. Port Winston is commonly upheld as one of the best examples of military engineering. Its remains are still visible today from the beaches at Arromanches, and a section of it remains embedded in the sand in the Thames Estuary, accessible at low tide, about 100 m off the coast of the military base at Shoeburyness.
[edit] Harbour elements and code names
Below are listed brief details of the major elements of the harbours together with their associated military code names.
[edit] Corn cob
'Corn cobs' were block ships that crossed the channel either under their own steam or that were towed and then scuttled to create sheltered water at the five landing beaches of 'Sword', 'Juno', 'Gold', 'Omaha', and 'Utah'. Once in position the "Corn Cobs" created "Gooseberries".
[edit] Gooseberry
The sheltered waters created by the Corn Cob block ships. Two of the "Gooseberries" grew into "Mulberries", the artificial harbours.
[edit] Mulberry
Mulberry was the code name for the artificial harbours. These were the "Gooseberries" which metamorphosed into fully fledged harbours. There were two harbours, Mulberry 'A' and Mulberry 'B'. The 'Mulberry' harbours consisted of a floating outer breakwater called "Bombardons", a static breakwater consisting of "Gooseberries" and reinforced concrete caissons called "Phoenix", floating piers code named "Whale" and the pier heads code named "Spuds". These harbours were both of a similar size to Dover harbour.
[edit] Mulberry 'A'
The Mulberry harbour assembled on Omaha beach at Saint-Laurent-sur-Mer for use the American invasion forces. Mulberry 'A' was so badly damaged by the Channel storms of late June 1944 that it was considered to be irreparable and its further assembly ceased.
In American use the Mulberry harbour was thought of as a disposable item and only intended for use for a few weeks. The result of this being in their haste to construct it they failed to securely anchor the completed harbour to the sea bed, which is why Mulberry A was destroyed in the storm and Mulberry B survived.[citation needed]
[edit] Mulberry 'B'
The Mulberry harbour assembled on Gold beach at Arromanches for use by the British and Canadian invasion forces.
[edit] Golden Arrow
'Arrow' the code name for the port at Arromanches and 'Golden' a reference to the Gold beach sector.
[edit] Bombardon
Large floating breakwaters fabricated in steel that were anchored outside the main breakwaters that consisted of Gooseberries (block ships) and 'Phoenix' (concrete caissons). During the bad storms at the end of June 1944 these broke loose, and possibly caused more damage to the harbours than the storm itself.
[edit] Phoenix
Reinforced concrete caissons constructed by civil engineering contractors around the coast of Britain, collected and sunk at Dungeness, the Cant and Selsey Bay, and then later re-floated and towed across the channel to form the "Mulberry" harbour breakwaters together with the "Gooseberry" block ships.
[edit] Whale
The dock piers were code named "Whale". These piers were the floating roadways that connected the "Spud" pier heads to the land. The roadways were made from purpose made torsionally flexible bridging units that had a span of 80 ft. mounted on pontoon units of either steel or concrete called "Beetles".
[edit] Beetle
Beetles were pontoons that supported the "Whale" piers. They were moored in position using wires attached to 'Kite' anchors.
[edit] Spud piers
The pier heads or landing wharves at which ships were unloaded. Each of these consisted of a pontoon with four legs that rested on the sea bed to anchor the pontoon, yet allowed it to float up and down freely with the tide.
[edit] Associated code names
[edit] Pluto
Pipe Line under the Ocean. Although 'Pluto' was not in itself an integral part of Mulberry, it was a vital part of the invasion technology. 'Pluto' consisted of four pipe lines, each 70 miles long, laid from the Isle of Wight to Cherbourg to supply fuel to the invading forces.
[edit] Further reading
- J.Evans, R.Walter, E.Palmer, 'A Harbour Goes To War: The Story Of Mulberry And The Men Who Made It Happen'. Publisher - South Machars Historical Society (2000), ISBN 1-873547-30-7
- Stanford, Alfred B., Force Mulberry: The Planning and Installation of the Artificial Harbor of U.S. Normandy Beaches in World War II, New York: William Morrow & Co., 1951 - details the design, assembly and construction of the American artificial harbor (Mulberry A) at Omaha Beach. Much of this book deals with the 108th Seabees, the unit which was responsible for construction of the Mulberry. Stanford was deputy commander of harbor during the invasion.
- Hartcup, Guy, Code Name Mulberry: The planning, building and operation of the Normandy harbours, David & Charles (Publishers) Ltd, 1977 - This book covers the background to Mulberry Harbours as part of Operation Overlord, the prototypes, the testing and development, the building (including contributions of suppliers) plus the installation and running. A book that covers the whole project very well.
- Institution of Civil Engineers, The Civil Engineer at War, vol 2. Docks and Harbours, 1959 - This is a collection of papers read at a symposium. They include a number of detailed plans and calculations contributing towards the final designs. Included are estimations of extracting power from waves by floating and stationary breakwaters.
