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Hydrodynamics, Or When To Escape From Alcatraz

Hydrodynamics, Or When To Escape From Alcatraz

New research reveals insights into 50-year-old escape attempt.

Wednesday, December 17, 2014 - 13:15

Chris Gorski, Editor

(Inside Science) -- At the annual meeting of the American Geophysical Union, currently underway in San Francisco, scientists are presenting research on everything from climate change to comets, and tsunamis to space weather. They're even using the tools of their trade to examine a prison escape from half a century ago.

The same techniques that can be used to forecast what could happen to San Francisco Bay as sea level rises in the coming decades can also be used to study tidal and current flow in the past. In the process, the scientists working on the project attempted to flesh out a famous prison escape. On the evening of June 11, 1962, three prisoners, Clarence Anglin, John Anglin and Frank Morris, disappeared and were never found. The inmates built rafts out of prison-issue raincoats and an adhesive, and then they left the island. One oar and a few small items from the prisoners were found on Angel Island, north of Alcatraz, but the escapees were never spotted.

The FBI stated that the prisoners probably drowned, but might have reached Angel Island. An episode of the television program "Mythbusters" examined the plausibility of the escape with a raincoat raft, and found that the tides made a direct path to Angel Island very unlikely.

Today, I met three European scientists who developed a model that suggests that where the prisoners headed probably depended on what time they shoved off from Alcatraz. The FBI report about the escape may have made some incorrect conclusions, they said.

I spoke to Olivier Hoes, from the Delft University of Technology in the Netherlands, and Fedor Baart and Gennadii Donchyts, both from Deltares, a research institute also in the Netherlands.

Their project started in a completely different direction. They were looking at what might happen in the San Francisco Bay area under different sea level rise scenarios. (They found that many of the islands will likely flood in the future.) But then, they realized they could use the same technique to look backward, and investigate the prison escape. 

Their work showed that the currents from the outgoing tide were so strong at the long-assumed time of departure, about 10 p.m., that the raft would have gone west toward the Golden Gate Bridge, and not north toward Angel Island. They may have drifted straight out to the ocean. If the prisoners left a bit later, they might have caught the tidal currents out toward the bridge, and then been able to reach shore when the tide slowed.

What the prisoners probably could not have done, they said, was row straight for Angel Island. The tides would have made that very unlikely. The simulations suggested that the best time to launch would have been 11:30 p.m., as that would have resulted in the prisoners landing near the Golden Gate Bridge, and also in debris washing up at Angel Island later.

However, Hoes said that we don't know how well the prisoners knew the tides and made plans to take advantage of them.

Hoes told me that their work might help make hydrodynamic simulations part of forensic investigations in the future. Baart suggested that their model could potentially help investigators figure out what happened in disappearances of boats and aircraft, although the constraints of the prison escape, with its well-defined starting point, was important to their success with this project.

To watch an animation based on the researchers' model, please follow this link to a simulation of where the raft likely would have gone, based on the time of departure. 

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Chris Gorski

Chris Gorski is an Editor for Inside Science and runs the Sports beat. Follow him on twitter at @c_gorski.