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The Ohio River, where it joins the Mississippi, was just centimeters below its forecast peak of 56 feet -- 16 feet above flood stage but well below the historic 61.72-foot peak of 2011, according to the National Weather Service.
Still, levee breaches in Alexander County, on the southern tip of Illinois, sent some residents fleeing and left others surrounded by water Saturday.
The river bulled through a levee in Thebes, Illinois, early Saturday, sending water rushing as far as six miles away from the Mississippi's usual banks, CNN affiliate KFVS reported
. Cities such as Miller City and Fayville were cut off, the station reported. But no injuries were reported.
"Everyone from those towns are accounted for," the station quoted Horseshoe Lake Fire Chief Michael Honey as saying. "Even the folks who chose to stay in their home and are now surrounded by water, authorities have made contact with them."
Illinois Gov. Bruce Rauner toured southern Illinois flooding Saturday and said the situation in Alexander County was among the worst he's seen.
"Some communities have actually been hit harder than the '93 flood," Rauner said Saturday, referring to the costly 1993 flood that saw parts of many communities along the Mississippi under water for months.
In Memphis, Tennessee, the Mississippi was expected to crest Friday well below record levels.
Still, by Saturday, flood waters had begun to approach structures on Mud Island, a peninsula jutting into the Mississippi River studded with upscale homes, apartments and a popular park.
The Shelby County, Tennessee, Office of Preparedness said Saturday that firefighters were going door-to-door, warning residents of the situation.
Memphis Chief Operating Officer Doug McGowen said the city government has been planning ways to deal with the flood for about a week, CNN affiliate WATN reported.
"We have all of our pumps that would take care of any flood waters in place, we have barriers in place. We learned a lot from the 2011 flood," he said.
In that flood, the river crested at 48.03 feet and inundated parts of the city's famed Beale Street and other neighborhoods, causing $2 billion in damage in Shelby County, Tennessee, alone, according to the National Weather Service.
The threat of significant flooding is forecast to persist through the week in parts of Missouri, Illinois, Kentucky, Tennessee, Arkansas, Mississippi and Louisiana, according to the National Weather Service.
The Mississippi is predicted to crest in Memphis on January 8; Greenville, Mississippi, on January 12; Vicksburg, Mississippi, on January 15; Natchez, Mississippi, on January 17; and Baton Rouge, Louisiana, on January 18, according to the agency's Saturday evening forecast
Flooding is also expected from the Arkansas and Ohio rivers and some tributaries.
In all, some 7 million people in 15 states were under threat of flooding, according to CNN meteorologists.
Cleanup in St. Louis County
In the St. Louis area, where the river crested Friday, some residents returned home and began the painstaking process of surveying the damage, cleaning up and salvaging whatever they could.
Several thousand people were forced to evacuate or suffered damage to their homes, hundreds of businesses also sustained damage, and hundreds of water rescues were conducted, Missouri Gov. Jay Nixon said.
The storms and floods killed 15 people in Missouri, officials have said. In Illinois, the death toll grew to nine with the discovery of an 18-year-old's body, according to Christian County Coroner Amy Calvert Winans.
On Saturday, President Barack Obama granted a request from Nixon for a federal emergency declaration to speed debris removal and relieve the strain of recovery costs in the St. Louis region.
Jason Peck of Eureka was one of those who returned home after the flood waters receded. He found that 3 to 4 feet of murky water had destroyed his basement and living room.
Eureka, a St. Louis suburb, is on the Meramec River, which empties into the Mississippi. The Meramec rose a record 35 feet in the last three days.
Recalling the damage to his son's room brought Peck close to tears.
"I didn't believe it was going to get like this," he told CNN.
His family had planned for the flooding, he said. They placed sandbags around the house and took other precautions. After midnight on Tuesday, however, the preparations appeared to be inadequate.
"We heard it was coming," he said of the flooding. "Then we heard some rushing water and went downstairs, and 3 o'clock is when it got real bad and (water) started shooting up through the drains."
Peck's son has not seen what's left of his bedroom. The family waited for an insurance adjuster. Peck said he has no flood insurance, but damage from a sewer backup may be covered.
"We have a lot of grossness in there," he said.
Nixon toured the city and was astonished by the devastation.
"I'm from this part of the state and, quite frankly, it's almost hard to believe," the Missouri governor said. "It's almost as if you're living on some other planet."