The Mississippi River has risen to levels in Memphis not seen since the 1930s, swamping homes in low-lying neighbourhoods and driving hundreds of people from their homes.
Officials were confident levees would protect Memphis landmarks such as Graceland and Beale Street.
As residents in the Home of the Blues waited for the river to crest at a projected mark just short of the record set in 1937, officials downstream in Louisiana began evacuating prisoners from the state’s toughest jail and opened floodgates to relieve pressure on levees outside New Orleans.
In Memphis, authorities have gone door-to-door to 1,300 homes over the past few days to warn people to leave, but they were already starting to talk about a labour-intensive clean up, signalling the worst was probably over.
“I want to say this: Graceland is safe. And we would charge hell with a water pistol to keep it that way and I’d be willing to lead the charge,” said Shelby County Emergency Management Agency director Bob Nations.
Talking about the river levels, he later added: “They’re going to recede slowly, it’s going to be rather putrid, it’s going to be expensive to clean up, it’s going to be labour-intensive.”
The main Memphis airport was not threatened, nor was FedEx, which has a sorting hub at the airport that handles up to 2M packages per day.
Forecasters said it appeared that the river was starting to level out and could crest as soon early today at or near 14.6m, just shy of the all-time high of 14.8m. Forecasters had previously predicted the crest would come as late as tomorrow.
The river was moving twice as much water downstream as it normally does, and the Army Corps of Engineers said homes in most danger of flooding were in places not protected by levees or floodwalls, including areas near Nonconnah Creek and the Wolf and Loosahatchie rivers.
About 150 corps workers were walking along levees and monitoring the performance of pumping stations.
Levees in the Memphis area are 17.7m high on average, and the floodwalls downtown are 16.5m.
Because of heavy rain over the past few weeks and snowmelt along the upper reaches of the Mississippi, the river has broken high-water records upstream and inundated low-lying towns and farmland.
The water on the Mississippi is so high that the rivers and creeks that feed into it are backed up, and that has accounted for some of the worst of the flooding so far.
Because of the levees and other defences built since the cataclysmic Great Flood of 1927 that killed hundreds of people, engineers say it is unlikely any major metropolitan areas will be inundated as the high water pushes downstream over the next week or so.
Nonetheless, they are cautious because of the risk of levee failures, as shown during Hurricane Katrina in 2005.