How the Storm That Destroyed D-Day Harbor Inspired Innovation

By L. Douglas Keeney

June 19, 1944, a formidable Atlantic storm strengthened and started to move toward the coastline of France. With a dark wall bearing furious winds and thundering waves twenty-feet high, it swept across the D-Day beaches of Normandy, casting about like matchsticks the 1,000-ton concrete caissons that formed the perimeter of a temporary harbor built off Omaha Beach.

When the storm subsided and daylight creased the sky June 22, the damage was a sight to see. Mulberry Harbor was gone.

The 75 concrete caissons called “Phoenixes” that had been linked together to form the breakwater was an indecipherable, half-sunken mash of concrete and steel. The floating pontoons and the flexible steel roadways six miles in length that had connected the piers to the beaches were tangled up like so much steel wool. Where tens of thousands of men had streamed ashore across floating coastal causeways there was only a coastal junk pile. Salvageable parts, including a caisson that was an impressive 60-feet wide by 60-feet tall and 200-feet long, weighing 6,000 tons, were simply towed down to the British beaches and used to reinforce their Mulberry Harbor also known as Port Winston. June 22, D-Day + 16, the harbor that had served Omaha Beach, was no more.

What emerged, however, was an idea—an idea so elegant that in years to come it would help open the Gulf of Mexico to oil exploration, allow the Navy to build temporary piers on the bare beaches surrounding Vietnam, and would make it possible for the Air Force to update an air base critical to Strategic Air Command near Thule, Greenland. What all ocean-based operations had in common was a susceptibility to the wave fronts generated by storm surges. The problem was that one could never predict wave heights and in the battle between Man-made structures and the ocean, the ocean invariably won. Leon DeLong, an engineer then on Omaha Beach, saw the twisted wreckage of the Mulberry and envisioned a pier that could be elevated before a storm hit thus allowing waves to sweep harmlessly beneath it. DeLong’s idea would become known as a “jack-up” pier or, in the case of offshore oil exploration, a “jack-up” oil rig. Massive jacks would grip the sides of steel legs and lift up above the waterline a platform or a pier. The idea was an instant success and height was scarcely a problem. Oil rigs in the Gulf of Mexico used DeLong’s invention and platforms were jacked-up 40 feet above the water; in the Atlantic, the Air Force radar stations called Texas Towers were jacked up 77 feet (DeLong thankfully walked away from this ill-fated project; Tower Four would collapse and take with it 28 men after rogue waves pummeled an already weakened structure).

Jack-ups were never used exactly as DeLong envisioned them—they were never used to quickly elevate a structure as a storm approached—but the mechanics were solid and the cost savings versus conventional construction techniques for piers and platforms were pronounced. Thus it was that from the tragedy of the D-Day tempest would emerge an idea that would ease the burdens of the Cold War and the Vietnam War, and help open the Gulf to exploration.


L. DOUGLAS KEENEY  is a military historian and researcher, and the author of 15 Minutes: General Curtis Lemay and the Countdown to Nuclear Annihilation. He is the cofounder of The Military Channel on which he hosted a series called On Target. He has since appeared on The Discovery Channel, CBS, and The Learning Channel and is the author of ten books of military history.

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