Mississippi River crests in Memphis

The Mississippi River has crested in Memphis at a height just centimetres short of the area's all-time record but still soaking low-lying areas with enough water to require a massive cleanup.

The soaking in Memphis was isolated to low-lying neighbourhoods, and forced hundreds of people from their homes, but no new serious flooding was expected. Officials trusted the levees would hold and protect the city's world-famous musical landmarks, from Elvis Presley's Graceland mansion to Beale Street, the famous thoroughfare known for blues music.

National Weather Service meteorologist Bill Borghoff says the river reached 14.58 metres at 2am on Tuesday (local time) and was expected to stay very close to that level for the next 24 to 36 hours. Reaching its high point means things shouldn't get worse in the area, but it will take weeks for the water to recede and much longer for inundated areas to recover.

"Pretty much the damage has been done," Borghoff said.

The crest is just shy of the record of 14.8 meters at Memphis reached during a devastating 1937 flood.

In many neighbourhoods, foul-smelling water approached the roofs of homes, and plastic bottles, garbage cans and rotting tree limbs floated on top. Residents said they've spotted snakes and fish in the water, while officials warned them of unseen bacteria.

Some greeted news of the river cresting with relief, but for others it was of little consolation. Rocio Rodriguez, 24, has been at a shelter for 12 days with her husband and two young children since their trailer park flooded.

Told by a reporter that the river had hit its high point, she said: "It doesn't matter. We've already lost everything."

Surrounding Shelby County and four others were declared disaster areas by President Barack Obama, which means that they'll be eligible for much-needed federal disaster aid. About 500 people were in shelters.

Bob Nations Jr, director of the Shelby County Emergency Management Agency, described on Monday what he expects to be slow and costly retreat by the high water: "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."

The slow-moving disaster was headed downstream to Mississippi and Louisiana, where residents were bracing themselves. Farmers downriver built homemade levees to protect their crops and engineers diverted water into a lake to ease the pressure on New Orleans levees. Inmates in Louisiana's largest prison were also evacuated to higher ground.

Meanwhile, Memphis declared that the city was open for business on Monday night. The local professional basketball team played a game as scheduled and a barbecue contest this weekend has been moved to higher ground.

"The country thinks we're in lifeboats and we are underwater. For visitors, its business as usual," said Kevin Kane, president and chief executive of the Memphis Convention and Visitors Bureau.

Besides Graceland, other popular Memphis sites were also spared, including Sun Studio, where Presley made some of the recordings that helped him become king of rock `n' roll and Stax Records, which launched the careers of Otis Redding and the Staple Singers.

The Mississippi River has broken high-water records upstream and inundated low-lying towns and farmland because of heavy rain over the past few weeks and melting snow. 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.