KROTZ SPRINGS, La. – Deputies warned residents Sunday to evacuate as Mississippi River water, gushing from a floodgate for the first time in four decades, crept ever closer to communities in Louisiana’s Cajun country.

Most residents heeded the warnings and headed for higher ground, even in places where there hasn’t been a trickle, hopeful that the flooding engineered to protect New Orleans and Baton Rouge would be merciful to their way of life.

Many started clearing out days ago, and by Sunday some areas were virtually empty as the water from the Mississippi, swollen by snowmelt and heavy rains, slowly rolled across the Atchafalaya River basin. It first started to come, in small amounts, into people’s yards in Melville on Sunday afternoon and was expected to reach Butte LaRose before midnight. Butte LaRose is some 50 miles downstream from the Morganza spillway. The floodwaters could reach depths of 20 feet in the coming weeks, though levels were nowhere close to that yet.

The spillway’s opening diverted water from heavily populated New Orleans and Baton Rouge — along with chemical plants and oil refineries along the Mississippi’s lower reaches — easing pressure on the levees there in the hope of avoiding potentially catastrophic floods.

It will be at least a week before the Mississippi River crest arrives at the Morganza spillway, leaving most people uncertain how much damage their property will sustain.

“It’s the unknown, that’s the problem,” said Krotz Springs town clerk Suzanne Bellau. “Is it going to come into their homes or not? And the people who are leaving, what are they coming back to?”