CBS News reports:

Only one of the 125, 10-ton steel floodgates on the 4,000-foot long Morganza Spillway in Louisiana was opened Saturday to prevent worse flooding downstream in New Orleans; a cautious first step to give everyone and everything a chance to flee.

“We’ll open one bay today. We’ll open one or two tomorrow and then we’ll open gates based upon the river conditions as they exist,” said Col. Ed Fleming, New Orleans district commander of the Army Corps of Engineers.

Here’s video of that one floodgate. It’s dramatic, particularly when you realize that it will release up to 10,000 cubic feet of water per second.