“This is why this system was built,” said Col. Ed Fleming, the Corps division commander in New Orleans. “It is in good shape.”

The Bonnet Carré was last opened in 2008, with peak flow at 160,000 cfs. That was the first time it was in use since 1997, and only 160 of its 350 bays were open.

Corps officials said they don't expect to open all the flood bays at either Bonnet Carré or Morganza.

Morganza has not been opened since 1973; it is triggered by a Mississippi flow of 1.5 million cfs at Red River Landing. The forecast is for a crest at 1.9 million cfs there.

At St. Francisville, La., high waters stopped the ferry service but officials opened the new John James Audubon Bridge ahead of time. The $409-million, 12-mile project was scheduled for completion late this year.