John Terret reports from Memphis on the struggles to cope with the deluge's havoc.
The worst floods to hit the central United States in more than 80 years have swallowed up homes, roadways and farms, as the Mississippi River swelled to six times its normal width.
Thousands of people have been evacuated from their homes as record spring flooding wreaked havoc in Tennessee. The surge is expected to sweep all the way to Louisiana at the southern end of the river.
"We're looking at some pretty substantial flooding all the way from Memphis (Tenessee's capital) to Louisiana," said Tom Bradshaw, a meteorologist with the US National Weather Service.
Daryl Hissong was one of those forced from their homes in Memphis, after water levels reached rooftops across his neighbourhood.
He said authorities forecast it would take "about a month" until the waters fully recede.
Meanwhile, the US Army Corps of Engineers (USACE) deployed about 150 workers to patrol the city's levees day and night to check for potential problems.
"We are very confident that the levee system is up to the test," USACE spokesman Jim Pogue said.
Levees and natural bluffs have protected most of Memphis from serious flooding, but those living in the affluent neighbourhood of Mud Island were struggling to keep the waters at bay.
The floods are the biggest in the Mississippi Valley since 1937, and the river has risen above levels recorded at that time in some areas, Bradshaw said.
"What is helping us is that we have a lot of levees we didn't have back in 1937 and they're able to control the water a lot better, so you don't see the massive displacement of folks and literally washing away of towns that you did in the old days," Bradshaw said.
But it will still take weeks for the river levels to return to normal and there are plenty of homes which could be lost, particularly in the low-lying Mississippi Delta.
Martin Moss, who lives near Horn Lake, Mississippi, said the potential flooding was hard to take after three weeks of tornado warnings and severe thunderstorms which hit the area last month.
"I could use a break from all this," said Moss as he packed up his possessions and stored them in his attic.
In Louisiana, the US Army Corps of Engineers partially opened a spillway that diverts the Mississippi into a lake to ease pressure on the levees in greater New Orleans.
The Corps has also asked for permission to open a spillway north of Baton Rouge, Louisiana's capital, for the first time since 1973.
Officials have warned residents that even if it is opened, they can expect waters 1.5m to 7.6m deep over parts of seven parishes. Some of Louisiana's most valuable farmland is expected to be inundated.