Mulberry Harbor - Arromanches

To supplement supply from landing craft on the beach, the British invented and built a pre-fabricated harbor, which they towed into place and assembled on the coast of France.  Two harbors were actually made, one at Arromanches for the British and another on Omaha Beach for the Americans.  A storm largely destroyed the Omaha Beach harbor, but the one at Arromanches was repaired and continued to function into the autumn of 1944, even after a number of ports had been captured.  Remains of the harbor are still visible, and there is a wonderful museum the town of Arromanches explaining it.

Design was begun in 1942 in reaction to the Dieppe Raid, when it became apparent that the Germans would keep French ports well defended.  In addition, in the Mediterranean the Germans showed their willingness and skill at destroying ports before their capture.  Winston Churchill was an eager proponent of the Mulberry Harbor concept.  Despite Churchill's enthusiasm, final construction of the pre-fabricated components was a rush job in the spring of 1944.  Assembly in Normandy began just a few days after D-Day.


Mulberry from Longues Battery

From Atop the cliffs to the west, you can make out the shape of the artificial port.  A rectangular shaped area was protected by blockships and pre-fabricated caissons.

This is the view from just outside the museum.  In the distance, you can see the remains of the caissons that protected the harbor.  On the beach, you can see the remains of the floats of the pontoon bridges, which came ashore in this vicinity.

Behind the protection of these breakwaters (foreground), bridges on pontoon bridges were built out to piers where ships could be offloaded (center and background).


These are the large concrete structures floated, towed really, across the Channel, then flooded so they would sink and form a barrier to high waves.  Unfortunately they were designed only for flooding, not for being pumped out, so they were immovable once sunk.  They were also liable to being swamped, so later version had a steel top despite the wartime shortage of steel.  Some of the caissons mounted anti-aircraft guns or barrage ballons.  Although the Luftwaffe had sustained heavy losses by this point in the war, the Mulberry Harbor was an inviting target.  In addition to here at Arromanches, casissons and blockships were used elsewhere to ease debarkment across beaches without the system of bridges and piers.  Floating devices known as bombardons were also placed further out than the caissons in the hope of protecting the harbor, but they were generally considered to be a failure.

Also towed across the Channel were the bridges and pontoons.  Maximum towing speed was just three knots.


The pontoons were anchored, stongly at Arromanches, not so strongly at Omaha Beach.  The bridging sections were designed to be flexible to account for the waves, and they were cabled together.  

This is one of the remaining bridging sections.  The round surface that you can see at the corner is where they sat on the pontoon.  The rounded surface allowed for the flex that was inevitable from waves and from vehicles passing.

Because of tides, a special floating piece was required at the end.  There were two bridges out to the pier, one for empty traffic going to the pier, one for full traffic coming to the beachhead. 

Most pontoons were made of concrete to conserve steel.  Some pontoon sections, like the one at left, were more securely attached to the bottom.  These steel pontoons were rigged to float up and down with the tides through poles that sat on the bottom.  The middle bridge span you can see is different than the ones on either side.  It is built to telescope, or expand and contract to account for tides and the movement of vehicles.


These are some of the remains of the pontoons.

There were seven platforms making up the piers.  They could be connected with expandable bridges and rectangular floats.


LST Unloading

This is a section designed for unloading LSTs, vehicles which would ordinarily beach themselves to debark directly onto the beach.  On the Mulberry Harbor, a flating wedge was designed for the LST to beach itself and unload from its bow.  In addition, the LST could be unloaded from its side, making for a much quicker operation.  Two LSTs could be unloaded in less than an hour.  And unlike a beached LST, one unloading at Mulberry would not have to wait many hours for the tide to allow them to leave, which could take six hours.

Like the pontoon bridge, the platforms of the piers were designed to move up and down with the tide on poles that rested on the bottom.  This meant that the ships, the platforms, and the bridges were always at the same level, insuring that the harbor could be used around the clock.


Some platforms were used for unloading Liberty ships.  Cranes were used.  Too late, it was determined that conveyor belts might have been more efficient.  The small vessel in the water is a DUKW, an amphibious truck.  A surprising percentage of the cargo was transported to shore by DUKW.


Also part of the logistics effort was 'PLUTO', a pipeline under the Channel made of lead, rubber, and steel - designed to bring fuel to the Allied troops.

Despite the efficiency of the Mulberry Harbor, the majority of men and materiasl arriving in France were deposited the old fashioned way, on the beach.  Because of this, and the failure of the Mulberry at Omaha Beach following the gale, some people question the wisdom and usefulness of the Mulberry Harbor.  However, it did give the Allied command the confidence to make a landing away from a major port, in an areas which were much less well defended. 

Copyright 2010 by John Hamill

Back to D-Day