Engineers will measure this flood by the depth of the Mississippi when it crests in Memphis, expected to be around 48 feet, and by the two million cubic feet per second of rushing floodwaters through the home of the blues.
The victims of this flood will measure it in what's lost -- submerged homes, gone possessions.
As people evacuate by the hundreds and search-and-rescue crews check the flood zone, four generations of Charles Hinkson's family took refuge at his house.
"We'll be on an island if it continues to rise. We're basically on an island now," Hinkson said. At his daughter's home, the floodwaters reached the roof Monday. Inside, they left their TV and furniture behind to make room for more important things to take, like a child's stuffed animal bear.
"I just want her to be happy. I just don't want her to feel like I feel, like everything has been ripped out from under you," Heather Hinkson-Davis said.
In Memphis, authorities have gone door-to-door to 1,300 homes over the past few days to warn people to clear out, but they were already starting to talk about a labor-intensive clean up, signaling the worst was likely over.
"Where the water is today, is where the water is going to be," Cory Williams, chief of geotechnical engineering for the Army Corps of Engineers in Memphis, told The Associated Press.
Exactly how many people heeded the warnings was not immediately clear, but more than 300 people were staying in shelters, and police stepped up patrols in evacuated areas to prevent looting.
Officials were confident the levees protecting the city would hold. Further down the river, outside New Orleans, floodgates were opened to relieve pressure on the levee system protecting the Crescent City. Lousiana's governor is urging residents to have a plan in case they need to get out.
La. Gov. urges residents to "prepare for the worst"
"Twenty-one parishes issued emergency declarations for this event. We expect that number to rise. Just like we say during hurricanes, hope for the best, prepare for the worst," Gov. Bobby Jindal (R) said.
The Mississippi River rose to levels not seen in Memphis since the 1930s, swamping homes in low-lying neighborhoods and driving hundreds of people from their homes. But officials were confident the levees would protect the city's world-famous musical landmarks, including Graceland and Beale Street, and that no new areas would have any serious flooding.
Aurelio Flores, 36, his pregnant wife and their three children were among 175 people staying in a gymnasium at the Hope Presbyterian Church in Shelby County. His mobile home had about 4 feet of water when he last visited the trailer park on Wednesday.
"I imagine that my trailer, if it's not covered, it's close," said Flores, an unemployed construction worker. "If I think about it too much, and get angry about it, it will mean the end of me."
Costly clean-up expected
Sun Studio, where Elvis Presley made some of the recordings that helped him become king of rock `n' roll, was not in harm's way. Nor was Stax Records, which launched the careers of Otis Redding and the Staple Singers. Sun Studio still does some recording, while Stax is now a museum. Graceland, Presley's former estate several miles south of downtown, was in no danger either.
Bob Nations Jr., director of the Shelby County Emergency Management Agency, expects an extensive clean-up once the river levels go down. "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 labor-intensive," he said.
Gov. Bill Haslam said late Monday that even though the river is approaching its crest, the flooding is far from over and water wouldn't recede in some neighborhoods for at least two weeks.
"It's not going to get a lot better for a while," Haslam said of the flooding in neighborhoods near the Mississippi's tributaries.
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 are 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.
With reporting by the Associated Press from Memphis, Tenn.