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RENA LARA, Mississippi -- Water from the swollen Mississippi River poured over a century-old levee Thursday, flooding 12,000 acres of corn and soybeans despite farmers' frantic efforts to shore up the structure. Downstream, officials with the Port of New Orleans said the Coast Guard could close the river to ships as early as Monday, halting traffic on one of the world's busiest commercial waterways.

After swamping low-lying neighborhoods in Memphis, Tenn., earlier this week, the rising water is bringing misery to farms and small waterfront communities in Mississippi, Louisiana and Arkansas. The Corps of Engineers is considering whether to open the Morganza spillway, which would flood thousands of homes and acres of farmland along a 100-mile stretch in Louisiana but take the pressure off levees and help to protect Baton Rouge, New Orleans and the oil refineries in between. A decision is expected in the next several days.

In Bunche's Bend, in the northeastern corner of Louisiana, there was heartbreak in the voice of farmer Ted Schneider, 50, as he watched the muddy river creep into his 2,800 acres of soybeans.

"It's kind of discouraging to look out here and think about all that work and money and know it is all going to be gone in a few days," said Schneider, who has farmed the land since 1984.

Maintenance on the levee was abandoned years ago after a higher levee was built farther back, leaving a sliver of farmland in between vulnerable. Officials are confident that levee will hold, but that's small comfort to the farmers whose land is flooding.

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About 40 of them worked in recent days to stack 1,800 sandbags along the older levee's weakest points, but their efforts were no match for the river, which crested higher than originally forecast.

Farther south, other communities were keeping a close watch on their levees and taking action to shore up potential trouble spots. Sandbags were being placed along a portion of New Orleans' French Quarter riverfront, though the city isn't expecting a major impact from the flood.

Chris Bonura, a spokesman for the Port of New Orleans, said the Coast Guard plans to close a 190-mile stretch of river from Baton Rouge to the Gulf of Mexico when the water reaches the 18-foot level at a gauge in Carrollton, which could happen by Monday.

The mouth of the Mississippi would become crowded with ships with nowhere else to go, though some might be diverted to other ports.

Barges headed south from the nation's heartland to the Port of South Louisiana at Reserve, upriver from New Orleans, would be unable to reach grain elevators. Massive ships that carry U.S. corn, soybeans and other crops out of the country would be unable to move. Shipments of Venezuelan heavy crude oil that come in by tanker to a refinery in Chalmette would be locked out of the river, though most refineries on the river are fed by pipelines.

In the poverty-stricken Mississippi Delta, meanwhile, people waited uneasily to see how high the water would get. About 600 homes in the Delta have flooded in the past several days as the water has risen toward some of the highest levels on record.

"It's getting scary," said Rita Harris, 43, who lives in a tiny wooden house in the shadow of the levee in Rena Lara, a town of about 500. "They won't let you go up there to look at the water."

The flood crest is expected to push past the Delta by late next week.

Mississippi Gov. Haley Barbour urged people to get out if they think there is even a chance their homes will flood. Tributaries are also backing up because the Mississippi is so high there is no place for the water to go. He said there is no reason to believe a levee on the Yazoo River would fail, but if it did, water would flow over small towns.

"More than anything else, save your life and don't put at risk other people who might have to come in and save your lives," he said.

In Hollandale, one of the small rural towns in the Delta the governor warned might flood if the levee breaks, 62-year-old nursing home worker Geraldine Jackson fretted about what to do if she and her husband have to leave their red-brick house, where pieces of the roof have broken off and the white trim is peeling.

"I have relatives, but all my relatives live in the Delta, and the water's going to get them too," she said. "I'm just real messed up."

Swollen by weeks of heavy rain and snowmelt, the Mississippi River has been breaking high-water records that have stood since the 1920s and `30s. It is projected to crest at Vicksburg on May 19 and shatter the mark set there during the cataclysmic Great Flood of 1927. The crest is expected to reach New Orleans on May 23.

Even after the peak passes, water levels will remain high for weeks, and it could take months for flooded homes to dry out.

In southeast Missouri, where floodwaters were receding, residents of hard-hit towns were getting their first look at the damage.

The Southeast Missourian reported Thursday that streets in the town of Morehouse, where about 280 homes were damaged, were lined with piles of ruined couches, beds, clothing and carpeting. The stench of mold filled the air.

"Everything was ruined. Even if it didn't get wet, it got mold on it," said Melissa Massey, whose home had five inches of water in it for five days. "Mold is growing up the walls right now."