Officials will open the flood gates of the Morganza Spillway at one sparsely populated part of Louisiana to protect the bigger cities of Baton Rouge and New Orleans to the South.
The cresting Mississippi has already caused flooding in other states. The latest effort in Louisiana will flood farmland and homes. About 25,000 people and 11,000 structures could be in harms way, the Associated Press reported.
The U.S. federal government began creating the system for handling rising waters after a 1927 flood, said Maj. General Michael Walsh of the U.S. Army Corp of Engineers.
These are water control programs we've been putting together for decades, Walsh said, according to the Sulphur Daily News.
The bays of the spillway will be used at only 25 percent of their capacity during this stretch. About 150,000 cubic feet of water per second will flow through.