Arromanches-les-Bains is the site of the famous Mulberry B Artificial Harbour and home to the D-Day Museum, better known as the Musée du Débarquement, Arromanches, which focuses on the astounding piece of engineering that still dominates the seascape today.

There were two Mulberry Harbours. Mulberry A at Omaha Beach, didn’t last long. A violent storm on 19th – 21st June destroyed much of it and it had to be abandoned, leaving Mulberry B (aka Port Winston) to handle the lion’s share of supplies for the allied forces in Normandy.

The Cunning Plan

Planning for D-Day started in March 1943, although it had been known since Jan 1942 that there would be an invasion, and the Allies, especially the USA, were already building up their men and materials in preparation. The problem was ships.

Flat-bottomed landing ships couldn’t deliver the assault forces and then go on to deliver the continuous stream of weapons, vehicles, men, fuel, armaments and equipment needed to sustain them in battle. That would have to be done by ordinary cargo ships. Thankfully, the USA was beginning to outstrip merchant ship losses to U-boats in the Atlantic with their Liberty Ship programme. The problem was that ordinary deep-keeled merchantmen needed a port to unload, and there weren’t any of those on the coast of Europe. Nor were any likely to become available quickly even if captured. The Germans would do all they could to sabotage them. So, the Allies had to build their own port. As Lord Louis Mountbatten said: “If we can’t capture a port we must take one with us.”

The coast of Normandy can be unforgiving to the unprepared.

Hmmm, not easy! I spent most of my teens & twenties sailing the Atlantic coast of France and those waters are tricky with a capital T! The tidal range is enormous. The Spring tide last Monday (6th) at Arromanches was 6 metres (almost 20ft)¹, and with all that water rushing out of the English Channel and then rushing back 6 hrs later, you can imagine what the currents are like – even inshore in the Baie de la Seine it can be as high as 3-5 knots. Then add weather; high winds, rough seas, wind against tide. The coast of Normandy can be unforgiving to the unprepared.

So, the plan starts with breakwaters, to afford ships large and small some protection and sheltered water. The allies decided to build breakwaters with floating ‘Bombardons’, scuttled ships and concrete ‘Phoenix’ caissons.

Bombardons were 200 ft concrete & steel tubes with a x-section in the shape of a cross. Three blades of the 2,000 ton Bombardon were below the water so the fourth made it look like a floating wall. They were strung together with fifty foot gaps between them and anchored to the bottom. Twenty-four bombardons would make up a mile of breakwater – and that was their function, to flatten out the wave movement. Bombardons and scuttled blockships were allocated to all the D-Day beaches. The breakwaters of the two Mulberry harbours at Arromanches (Gold) and Saint Laurent-sur-Mer (Omaha) were made up of blockships and Phoenix caissons scuttled 2 kilometres offshore.

At the end of May 1944, 55 old warships and cargo ships were gathered in Loch Linnie, Scotland where they were prepared for scuttling, with explosives and concrete ballast. Then they set off with an escort to join the gathering fleet for D-Day. Meanwhile on 4th June, 146 giant concrete ‘Phoenix’ caissons of varying sizes, which had been constructed in secrecy over the previous 9 months and then sunk to hide them, were refloated and began their slow (4 knots) journey to Normandy, towed by 85 tugboats.

You’ve got to admit, that is spectacular planning and organisation on a grand scale, and we haven’t even talked about the piers!

Again, all this has to work across a huge tidal range. So a great deal of testing was involved in designing the wharves and piers heads needed to unload a large share of the estimated 38-40,000 tons of supplies needed daily. 

Essentially the system works around huge wharf units fixed in position on four legs like an oil rig, and allowed to float up and down with the tide. This type of wharf is called a “Spud” wharf, but the wharf units in the Mulberry harbours were called Loebnitz wharves². These are connected to the shore by a flexible roadway up comprising 80 ft bridging spans on floating concrete pontoons (“Beetles”). The causeways could be up to a kilometre long in order to place the wharves in water deep enough to allow a fully laden cargo ship alongside at low tide.

There were several causeway & wharf platforms (piers) at Mulberry B to allow for unloading offshore. The east pier was the pier for unloading tanks, bulldozers, artillery and other military vehicles from LSTs (Landing Ship Tank). It had one causeway because all the traffic was self-driving.

The main wharf was made up of seven platforms, allowing up to seven ships at a time to be unloaded. This was the general supplies wharf (food, medicines, clothes, materials, equipment, etc). This had two 1.2 kilometre floating causeways so a continuous stream of empty trucks could drive out on one, load up, and return to shore on the other.

To the west of the main wharf there is the pier for ammunition barges, and west of that, an interesting pier called a ‘Swiss Roll‘. It was a floating road surface, which in trials had proved capable of handling light vehicles up to 7 tons.

What’s left at Arromanches now?

Well, the striking thing about the little town of Arromanches is the seascape. You can still clearly see twenty or so of the Phoenix caissons forming the semicircular breakwater out to sea, and piled up on the beach, a set of concrete Beetle pontoons that supported one of the causeways 75 years ago.

The Phoenix caissons came in different sizes, up to 70m long, to fit different parts of the breakwater. There’s only one example of the largest Phoenix caissons (No. 36), standing slightly by itself in the middle of the semicircle. It is around 20 m high and is thought to weigh as much as the Eiffel Tower – 7,000 tonnes.

The D-Day Museum

The museum is in prime position on the waterfront, looking out over the remains of Mulberry B. It is a small building so, once you take out the space needed for a small library, a shop and a cinema, there are not many exhibits on display.

However, its centrepiece is a set of educational working models in front of the panoramic windows looking out to sea. These explain what you are looking at out there, and how the port worked.

What else?

I rather liked seeing the Napier Sabre engine from a crashed Hawker Typhoon that was shot down by German anti-aircraft fire near Arromanches. They are impressive engines. There’s an intact version of the later Sabre III engine in the RAF Museum in London. The Typhoon was a ground attack aircraft that harried the German forces trying to hold back the invasion. In front of the engine is a replica of the rockets they fired.

Outside the museum there are some interesting items, including a Mk III 5.5″ field gun, a searchlight and Ack-Ack gun from a Phoenix caisson. There is also a standard 80 ft section of the causeway bridge span designed by Major Alan Beckett, and a memorial to his design genius.

Early on in the planning stage Churchill had, in a few words, identified one of their biggest problems – keeping the causeways in place. “Piers for use on beaches: – They must float up and down with the tide. The anchor problem must be mastered – let me have the best solution worked out. Don’t argue the matter. The difficulties will argue for themselves,” he wrote. Alan Beckett rose to the occasion, designing the roadway spans, Beetle pontoons and a new kind of “kite” anchor to hold them in place.

Visiting Arromanches

There is more than one element (the museum) to visiting Arromanches, so you might want to spend a few hours there². 

You should take time to walk down onto the beach if the tide is out, and inspect the Beetle pontoons close up.

You  should walk or drive up to the east cliffs where there are panoramic views of the Mulberry B breakwater caissons, and Arromanches 360, a cinema showing a 360° documentary about D-Day and the first 100 days of the Normandy campaign. 

Arromanches can get pretty busy, particularly with coach parties and school groups. We visited on a weekday at the beginning of April and it was hard to move in the museum (and very hard to take photos) where there was a continuous stream of French (mostly) and English school groups passing through. It’s great that so many school kids get a chance to explore WW2 history, and I’m totally not complaining about it. When I asked the staff if there are any quieter days to visit, they said “only the weekend”! So my advice would be to go early on a Saturday or Sunday in the summer season.

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¹ The highest range at Arromanches can be as much as 8 metres.

² These wharves were based on a dredger designed & manufactured by Lobnitz and Co in Renfrewshire, who then made the Mulberry version.

³ There are a number of eateries in the town centre. We rather liked the grand old style of the Hôtel de Normandie for lunch. Parking can be expensive. If you go out of season you may be able to find places to park for free in the backstreets.

Declaration: I was on a self-driving press trip as a guest of the Normandie and Calvados tourist offices. Museum entry was complementary.

 

Further reading…

• The D-Day Center (who loaned me their map) has some great content on visiting Normandy.
• Mulberry Harbour Info focuses on the trials & development of Mulberry components in Scotland
• Combined Operations has a quite detailed post on the Mulberry harbours.
• HKSW has some really good drawing of Mulberry components, inc a good one of Bombardons