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Flow models of San Francisco Bay

Dutch scientists Olivier Hoes, Rolf Hut and Fedor Baart came to San Francisco to discover what happened to the three Alcatraz inmates who set out in a raft made of raincoats into the treacherous waters of San Francisco Bay on the night of June 11, 1962. Using state-of-the art, hydraulic software, coastal engineer Olivier Hoes created one of the most sophisticated flow models of San Francisco Bay ever built.

1. alcatraz-currents-1

The actual San Francisco bay is very shallow. It’s just 4 or 5 meters deep. But in the center, it is about 20 or 30 meters deep. Every time when the tide is going in or out there’s one big valley of water flowing in and out.

Rolf Hut realized if they could use 3D computer modeling to forecast future bay conditions – they could also use 3D modeling to look into the past.

2. AlcatrazCurrents-4

3. AlcatrazCurrents-3

The GIFs 2 and 3 above predict how a raft would probably be carried leaving Alcatraz. These show the paths of 50 virtual rafts launching from Alcatraz on the night the escape. What the Dutch scientists discovered from these flow models is the first scientific proof the inmates could’ve survived.

The study of the Dutch scientists revealed that the timing was crucial to get to the shore on the other side and that it actually depended enormously on when they left. To escape and survive, the inmates would have had to launch during a narrow window between 11:30pm and 12 midnight. If they did, the findings suggest the inmates could have ridden the outgoing tide to an unexpected place. For decades, common wisdom said that the escapees headed for the land mass nearest Alcatraz: Angel Island. But the Dutchmen think this would’ve been a fatal mistake. Based on the currents, that trajectory would have swept the men out to sea.

4. AlcatrazCurrents-1

5. AlcatrazCurrents-2

To tackle the mystery of what happened to Morris and the Anglins – the Dutchmen used old tidal charts to build a 3D model that recreates the currents from the night of the escape.

A deep underwater canyon cuts right in front of Horseshoe Bay. It creates a narrow, 300-foot-wide wall of water flowing in and out through the golden gate.

Secrets of the Dead: The Alcatraz Escape, premieres nationally Tuesday, March 29 at 9 p.m. on PBS (check local listings).



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