Hundreds gathered at the massive Bonnet Carre Spillway in St. Charles Parish on Sunday morning to watch as it was opened for the first time in four years.

At the opening ceremony, the U.S. Army Corps of Engineers (who provided the above video), praised the wisdom of “our forefathers” for creating the spillway more than 80 years ago.

The Corps uses it to ensure that the rising river doesn’t overwhelm the levees in and around New Orleans, said Wehr, who climbed into a crane shortly after 10 a.m. to ceremonially remove the spillway’s first 10 “needles”: 11-foot-long timbers about 8 inches by 12 inches in diameter.

The structure features 350 linear bays of 20 needles each. All told, 400 of the needles were removed Sunday, opening up 20 bays. The Corps will remove more timbers each day as needed to divert water from the rising river. Officials said 30 bays could be opened Monday, depending on the river’s speed and level.

When it’s completely open, the spillway is designed to divert 250,000 cubic feet of water per second away from New Orleans and the lower portion of the river. It’s unclear how many bays will ultimately open this year or how long they will remain open.