Here, in its entirety, is the incredibly moving, just-released, Tom Hanks-narrated, 11-minute documentary of the largest-ever evacuation by boat in history.

In nine hours, boats streaming in from all over the Northeast evacuated 500,000 people trapped on Manhattan Island by the complete shutdown of all trains and bridges in the wake of the fall of the twin towers. (Compare that with history's second-biggest evacuation, of 339,000 soldiers and civilians from Dunkirk, in WWII, which took nine days.)

One of the things this event illustrates is that in cities present and future, redundancy is one of the keys to resilience. New York has long neglected its waterfront, and in the face of rising seas it is even occasionally seen as a liability . And yet without access to the water, a half million New Yorkers would not have made it home on 9/11.

This documentary was produced by Road2Resilience, part of an effort by the Center for National Policy to "build the reflexes and instincts necessary at every level of American society to respond quickly and wisely to future crises."

This post was originally published on Smartplanet.com