Charleston - A storm system dumped almost 230mm of rain on parts of West Virginia, trapping 500 people in a shopping centre when a bridge washed out, and dozens of other people had to be plucked off rooftops or rescued as waters quickly rose during the deluge.
At least 14 people are said to have died.
Greenbrier County Sheriff Jan Cahill on Friday described "complete chaos" in his county, which appeared to be the hardest hit.
"Roads destroyed, bridges out, homes burned down, washed off foundations," he said. "Multiple sections of highway just missing. Pavement just peeled off like a banana. I've never seen anything like that."
Water rescue teams were searching devastated areas.
"Today's just an accountability mission, trying to verify where everybody's at and follow up on missing person tips," he said. "It's really hard to navigate around because there's just a ton of debris. We've even had rescuers that had to be rescued."
The rains submerged homes and cars in dirty brown water and chewed up roads. Tens of thousands of people were without power at the peak of the storm.
Some areas are "probably looking at flooding that's going to be the worst in 100 years," Governor Earl Ray Tomblin's spokesperson Chris Stadelman said.
Eric Blackshire was one of the stranded at Crossings Mall, a mix of restaurants, stores and a hotel in Elkview, which is about 25km northeast of Charleston. Some had to sleep in their cars or at businesses overnight. Blackshire opted for a hotel room.
"It was kind of like a hurricane party. I guess you could call it a flood party. There were lots of beers being drank last night," he told The Associated Press.
He was able to get to safety on Friday when Pinch Volunteer Fire Department firefighters used a rope to guide people down a hillside. About 50 people had been rescued so far.
Kanawha County Sheriff's Office spokesperson Sergeant Brian Humphreys said a better solution was needed: "That's going to require, I think, some engineering efforts" - perhaps a temporary bridge.
An area near the West Virginia-Virginia border received at least 230mm of rain while other parts of the state had between 80mm and 120mm, National Weather Service hydrologist John Sikora said. While most of the rain had tapered off on Friday, there were still scattered showers, thunderstorms and river flood warnings.
Kanawha County officials reported at least 70 water rescues.
"We had swift water rescue teams out until late last night and back out again this morning literally rescuing people from rooftops and upper stories of houses," the governor's spokesperson said.
The heaviest rainfall was in Greenbrier County. At The Greenbrier, a luxury resort nestled in the mountains, the golf course was overrun by rushing waters. The course is scheduled to host a PGA tour event, The Greenbrier Classic, from July 4-10.
Prayers, not golf
"It's like nothing I've seen," owner Jim Justice said in a statement. "But our focus right now isn't on the property, golf course or anything else. We're praying for the people and doing everything we can to get them the help they need."
Professional golfer Bubba Watson was apparently visiting the resort and tweeted photos of entire holes underwater: "Prayers for @The_Greenbrier & surrounding areas. We are without power & it's still raining. Never seen this much rain! #WestVirginiaBeSafe."
The governor issued a state of emergency on Thursday for 44 counties in the state.
"I have authorised the deployment of up to 150 members of the West Virginia National Guard to assist local emergency responders as we continue to evaluate the situation today," he said in a statement on Friday.Across the state line, Virginia Governor Terry McAuliffe declared a state of emergency in Alleghany County and Covington. Three emergency workers were injured during a water rescue in Alleghany County, officials said.