(CNN)The nightmare was only beginning for Matthew Rigney and his partner, Danielle Hall, when floodwaters swept her away from him and their four children Saturday in Middle Tennessee.
While Hall clung to a tree, the father held onto their children in their flooded house until two of them -- 7-month-old twins -- were swept out of his arms during the deadly flooding in the Waverly area, the family told CNN affiliate WZTV.
Now, the devastated couple, survivors of the flash flooding that killed at least 18 people, are planning the funerals of their babies, Rileigh and Ryan.
Remembering the babies as "happy," Hall told CNN affiliate WZTV on Monday, "They made our life complete."
CNN has tried unsuccessfully to reach the couple.
Dozens of residents were quickly overtaken by flash flooding brought on by Saturday's heavy rain. More than 270 homes were destroyed.
Mother had stepped outside for help
The family's ordeal began when a transformer blew around 6 a.m., waking them up. Before they were able to get up and leave, "water was coming in the house," Rigney told CNN affiliate WSMV.
Around the area, raging waters were pulling homes off their foundations, leaving cars and other debris strewn about, and washing away much of what was in its path.
Hall went outside to seek help, but "the water just took me," and "the only thing I could hang onto was a tree," she told WSMV.
Meanwhile, water was filling the home, trapping Rigney and their four children -- the oldest of whom is 5 -- in a back bedroom, WSMV reported.
Water hit, and 'that's when I lost them,' father says
Rigney tried to get out a window with his children, "but the water was coming in so fast, we couldn't even get out," he told WSMV.
He clung to them.
"And when the water hit and the room filled up, that's when I lost them -- I lost all of them," Rigney recalled to WSMV.
His two older daughters -- 5 and 1 -- surfaced, but the twins did not. "It was the worst experience I've ever had," he told WSMV.
As Rigney and the two older daughters struggled, a neighbor climbed onto their roof and pulled them to safety, WSMV reported.
Rileigh and Ryan Rigney, 7-month-old twins, were swept away in Saturday's flooding.
Mother says she clung to a tree for hours
Hall remained in the rushing water for hours, holding onto the tree.
"The whole time I held onto a tree, for six and a half hours, screaming that I had babies at the house that needed rescue," she told WZTV.
Hall eventually was rescued. "When I finally got saved, I was searching for (the four children), because I knew (Rigney) was alive. I didn't know (about) my babies," she told WZTV.
The twins were among those who died in the flooding, Humphreys County Emergency Management Agency spokesperson Grey Collier told CNN.
Photos: Deadly flooding in Middle Tennessee
People walk across a washed-out road in Waverly, Tennessee, on Sunday, August 22.
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Photos: Deadly flooding in Middle Tennessee
Cars that were swept up in floodwaters sit on the banks of Waverly's Blue Creek on Monday, August 23.
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Photos: Deadly flooding in Middle Tennessee
Dustin Shadownes of the Ashland City Fire Department is joined by a cadaver dog as he searches a Waverly creek for missing people on August 23.
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Photos: Deadly flooding in Middle Tennessee
John Curtis, co-owner of the Waverly Cash Saver grocery store, walks through his damaged store on Sunday, August 22.
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Photos: Deadly flooding in Middle Tennessee
Kalyn Clayton, 16, surveys the damaged kitchen of a Waverly home while volunteering with his church youth group on August 22.
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Photos: Deadly flooding in Middle Tennessee
A building is left in the middle of the road in Waverly.
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Photos: Deadly flooding in Middle Tennessee
Brian Mitchell, right, is joined by friend Chris Hoover while looking through his mother-in-law's damaged Waverly home on August 22.
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Photos: Deadly flooding in Middle Tennessee
Navy Haley helps remove belongings from a home while volunteering in Waverly.
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Photos: Deadly flooding in Middle Tennessee
Vehicles are submerged in Trace Creek as a result of the severe weather in Waverly.
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Photos: Deadly flooding in Middle Tennessee
Anthony and Vanessa Yates find their wedding wreath in their flood-damaged home in Waverly, Tennessee, on August 22. Vanessa was at home with her 4-month-old daughter when the floodwaters rapidly rose. They were rescued by Vanessa's brother-in-law, Alan Wallace, who paddled his kayak to their house.
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Photos: Deadly flooding in Middle Tennessee
Cars and debris are stacked high along Simpson Avenue in Waverly.
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Josh Whitlock and Stacy Mathieson look through what is left of their home after it burned down following flooding in Waverly.
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Authorities found the babies' bodies together, Rigney and Hall told WSMV.
The infants' funerals are scheduled for Wednesday and Thursday, according to WZTV.
Ryan "was my one and only boy that I prayed so hard for, and he always smiled -- that boy was the happiest baby I've ever seen in my life," Hall told WZTV.
As for Rileigh: "She was a diva. She was a drama queen. She had to have all the attention," Hall told WZTV.
Saturday rainfall totals reached 17.26 inches north of Centerville, in Hickman County; 17.02 inches in McEwen, in Humphreys County; and 13.76 inches near Dickson, in Dickson County, the National Weather Service in Nashville said.
The flooding on Saturday was caused by several storms training over the same area. Extreme rainfall rates are becoming more common because of human-caused global warming, scientists say.
