MEMPHIS — The Coast Guard closed a stretch of the swollen Mississippi to barge traffic Friday in a move that could cause a backup along the mighty river, while police farther south in Memphis went door to door, warning thousands of people to leave before they get swamped.
Emergency workers in Memphis handed out bright yellow fliers in English and Spanish that read, "Evacuate!!! Your property is in danger right now."
All the way south into the Mississippi Delta, people faced the question of whether to stay or go as high water rolled down the Big Muddy and backed up along its tributaries, breaking flood records that have stood since the Depression.
Because of levees and other flood defenses built over the years, engineers said it is unlikely any major metropolitan areas will be inundated as the water pushes downstream over the next week or two, but farms, small towns and even some urban areas could see extensive flooding.
"It's going to be nasty," said Bob Bea, a civil engineer at the University of California at Berkeley who investigated levee failures in New Orleans after Hurricane Katrina in 2005.
How bad it gets depends on how well the flood protection systems have been built and maintained, he said.
The Coast Guard closed a five-mile stretch of the Mississippi to protect Caruthersville, Mo., and said barges could be banned for up to eight days. The fear was that the wake from big boats would push water over a floodwall and into the town of 6,700.
Lynn Muench, a vice president of the American Waterways Operators, an industry group, said the eight-day shutdown would have a multimillion-dollar effect on the barge industry and slow the movement of many products.
"It's just like if you took out every bridge going over the Mississippi what that would mean to railroad and vehicle traffic," Muench said.
In Tennessee, local authorities were uncertain they had legal authority to order evacuations and hoped the fliers would persuade people to leave. Bob Nations, director of emergency management for Shelby County, which includes Memphis, said there was still time to get out.
The river is not expected to crest until Wednesday.
About 950 households in Memphis and about 135 other homes in Shelby County were getting the notices, Shelby County Division fire Chief Joseph Rike said.
Farther south, parts of the Mississippi Delta began to flood, sending white-tail deer and wild pigs swimming to dry land, submerging yacht clubs and closing floating casinos.
Bea, the civil engineer, said he is concerned because some levees across the United States have been built with inferior dirt, or even sand, and have been poorly designed.
"The standards we use to build these things are on the horribly low side if you judge them by world criteria and conditions," he said. "The breaches, as we learned in New Orleans, are the killers."
How long the high water lingers, and how much damage it does to the earthen walls of the levees as it goes down, are crucial factors.
"The whole summer will have to be watched," said J. David Rogers, a civil engineer at the Missouri University of Science and Technology.
MONTPELIER, Vt. — Already at its highest level ever, Lake Champlain surpassed flood stage by 3 feet Friday, leaving hundreds of homes destroyed or damaged in a slowly unfolding catastrophe on island communities and the New York and Vermont sides of the 120-mile-long lake.
Teams from the Federal Emergency Management Agency will be in Vermont on Tuesday to begin assessing damage, said spokesman Dennis Pinkham. Authorities said it could be weeks before floodwaters recede.