|Al Jazeera's John Terret reports from the Mississippi where people are fleeing the worst flooding since 1927
People and animals in their thousands sought higher ground to escape the flooding from the Mississippi River and its tributaries as water flowed over levees and the Coast Guard planned to halt traffic on one of the world's busiest commercial waterways.
Chris Bonura, a spokesperson for the Port of New Orleans, said on Thursday that the Coast Guard planned to close a 306km stretch of river from Baton Rouge to the Gulf of Mexico.
He said that this could happen by Monday.
In Louisiana, 12,000 acres of corn and soybeans were flooded. The US Army Corps of Engineers considered whether to open the Morganza spillway, which would flood thousands of homes and acres of farmland but help to protect Baton Rouge, New Orleans and the oil refineries in between.
The mouth of the Mississippi would become crowded with ships with nowhere else to go, though some might be diverted to other ports. Massive ships that carry US 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.
Meanwhile, in the poverty-stricken Mississippi Delta, 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.
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 latest round of flooding in what has been an extremely wet spring after a snowy winter in parts of the US Midwest will force the US Army Corps of Engineers to make more difficult decisions like it did earlier this week.
Earlier this week, the Army Corps blew up a levee that relieved pressure on towns upstream but inundated dozens of Missouri farms and tens of thousands of fertile acres.