KROTZ SPRINGS, La. — The knock on Wayne Duplechain’s door came at 8 a.m. Sunday — deputies telling him it was time to head for higher ground.

Duplechain and his family live about eight miles down the Acthafalaya River from Krotz Springs in an area of St. Landry Parish that was under a mandatory evacuation order one day after the U.S. Army Corps of Engineers began opening the Morganza spillway.

The opening diverts water from the Mississippi River — unusually high right now because of snow melt and heavy spring rains — into the largely rural area of the Atchafalaya Basin. It eases the flood threat for heavily populated metropolitan areas downriver, but it meant Duplechain had to start thinking about protecting his property.

And leaving.

“I’m going to pack my family up, but I’m going to try to come back,” said Duplechain, who said he believes St. Landry authorities ordered the evacuation too soon. Sandbags were piled 2 feet high around his house and he has a generator and a boat to escape in if the river gets too high. He thinks that possibility is several days away.

“The river isn’t going to get over the levee. It’s the backwater that’s going to get us,” he said. The backwater is from a swamp in his backyard that abuts a federal hunting reserve.

“It’s going to be slow-rising, so I’ll get out if I have to. I’m not totally stupid.”

Two massive spillway gates were opened Saturday and the Corps said it was opening two more Sunday. Wild hogs, rabbits and deer could be seen fleeing the moving water Sunday morning, Lt. Col. Joey Broussard of the state Wildlife and Fisheries Department said after a helicopter ride over the spillway.

“Water could start to flow into Krotz Springs in the next eight to 24 hours, and that’s an estimated guess as the water is moving very, very slowly.”

Opening the Morganza, and the earlier opening of the Bonnet Carre Spillway near New Orleans, were having the desired effect at New Orleans. The Mississippi was cresting there at 17 feet above sea level — lower than forecasts had predicted before the opening of the Morganza. The level is above flood stage but below the 20-foot threshold of protection afforded by levees.

Higher water makes the current faster and the river more difficult to navigate. The Coast Guard had warned that lower Mississippi River traffic might be closed at New Orleans if a key gauge there reached 18 feet.

“There’s almost no chance we will have any significant restrictions or closures,” Chis Bonura, spokesman for Port of New Orleans, said.

After a six-day closure of the vital commercial artery in 2008 because of a fuel spill, the port estimated that the national economy lost as much as $275 million a day.

Relief for New Orleans meant hardship for others.

Krotz Springs town clerk Suzanne Belleau said 500 to 700 residents live outside the town’s protective levees. They were subject to Sunday’s St. Landry evacuation order. She didn’t think the sheriff’s department would force people to leave.

“It’s mandatory, but if people choose to stay, they can stay,” she said.

Jake Nolan, 23, said National Guardsmen who knocked on his door Sunday advised him to keep white towels on hand and make sure he has access to the roof of his home if he stays — in case he needs to signal rescuers. That didn’t appear to be part of any official instructions, though Nolan, his wife and their three children didn’t plan on staying.

“I don’t want to be stuck here if the water does get bad,” he said.