Nine gates of the Morganza Spillway are now open and Sunday afternoon, water was beginning to creep into low-lying areas in St. Landry Parish.
"Water is showing up in some areas, but nothing serious yet," said Jessie Bellard, parish government's director of administration.
"The Krotz Springs campground is covered. The water is coming in faster than we thought," said Bellard, who added that no serious problems are anticipated until later this week.
"They are telling us the levees should hold it," Bellard said.
In Melville, the town closest to the spillway, Police Chief John McKeel said the water is rising, but at a slow pace.
"Things are going pretty good right now. The real test will be Tuesday, possibly Wednesday," McKeel said.
A mandatory evacuation order is in place for most areas along the levee on the eastern side of the parish and Bellard said everyone has been notified.
"The evacuation went well. We are just about complete," said Bellard, though he added a number of people are refusing to leave.
One of those is Wayne Duplechain, who lives about eight miles outside Krotz Springs. Duplechain said his family has evacuated but he plans to stay and ride out the flooding.
He has three layers of sandbags stacked around his ranch-style, brick home and figures the water won't start lapping against them for seven or eight days.
"It's going to be slow-rising, so I'll get out if I have to," said Duplechain, who has a generator and boat ready if he has to get out in a hurry. "I'm not totally stupid. If it comes over the sandbags, I'm leaving."
The first of the 125 gates of the Morganza Spillway was opened at 3 p.m. Saturday, marking the first time in 38 years and only the second time in its history that the flood control structure has been utilized.
Another gate was opened later Saturday and two more Sunday.
While no more gates are expected to be opened today, Col. Ed Fleming, the U.S. Army Corps of Engineers' New Orleans district commander, said he expects to eventually open a fourth of the gates.
He said the openings will be done at a slow pace to prevent scouring, give residents the opportunity to evacuate and give animals a chance to escape the rising water.
Lt. Col. Joey Broussard with the Louisiana Department of Wildlife and Fisheries said animals seem to be getting the message, pointing out that deer, hogs and rabbits are already fleeing the rising water near the floodgates.
Opening the spillway sends hundreds of thousands of gallons of Mississippi River water into the Atchafalaya Basin.
The Mississippi is already in flood, breaking river-level records that have stood since the 1920s in some places.
Opening the spillway, while potentially threatening thousand of residents, businesses and camp owners, is designed to head off an even greater disaster by relieving pressure on levees from Baton Rouge to New Orleans.
The Associated Press contributed to this story.