Meanwhile, Hurricane Frances strengthened as it churned near islands of the northeastern Caribbean with ferocious winds.
The eight named storms this month — through Hermine — are a record, reports CBS News Correspondent Mark Strassmann.
In the city's hard-hit Shockoe Bottom district, dozens of cars that had been carried off by the raging floodwaters were strewn about the streets, which were caked with mud and scattered with bricks and other debris. Numerous businesses and apartments were flooded. A produce truck lay overturned. A brick building had collapsed onto several vehicles.
Residents and city officials described a scene of terror as floodwaters fed by a foot of rain swept through the low-lying area on Monday, reaching depths of up to 10 feet. Rescue crews helped lift passengers out the windows of a marooned bus, and panicked motorists raced to escape their cars as the floodwaters engulfed them.
City officials closed off 20 blocks of the Shockoe Bottom district — or about half of the historic area — near the James River, declaring them off limits until the buildings can be inspected to make sure they are safe.
Officials said that the damage would easily be in the millions of dollars but that it was too early to provide an estimate.
"The devastation to a lot of the businesses in Shockoe Bottom is overwhelming," said Gov. Mark R. Warner, who walked through the muddy streets. He said he would ask Washington to declare a state of emergency, making residents eligible for federal aid.
The storm surprised meteorologists, who had forecast no more than 4 inches of rain. But the system parked itself over the Richmond area for several hours. Northeast of the city, rural King William County received 14 inches, the National Weather Service said.
"This truly was an act of God," the governor said.
Most of the buildings in the low-lying district are two- and three-story brick structures, primarily warehouses and other commercial buildings converted to restaurants, nightclubs and loft apartments. A few buildings date from before the Civil War.
In the 19th century, the Shockoe Bottom district was a thriving industrial center of tobacco warehouses and factories, most of which was reduced to smoldering ruins after the city fell to Union troops in 1865. Abraham Lincoln walked through and surveyed the damage.
A floodwall built in the 1990s protects shops, restaurants and homes, but it was designed to hold back the James — not a sudden deluge from the sky.
On Monday, rushing water swept away cars and trucks and smashed them into buildings.
Luissa Alba, who was rescued from her apartment building by boat, said she saw one person trying to escape the rising floodwaters by clinging to a railroad trestle. A woman holding a child in each arm stood on top of her car, screaming for help, she said.
Alba, a 28-year-old graduate student, said that for some reason, she could not reach a 911 emergency dispatcher on her cell phone.
"It was ridiculous," she said. "We basically had to call friends who called 911 for us."
Andrea Hughes, who lives in a Shockoe Bottom apartment, said she watched from the roof of a flooded pizza restaurant where she works as a river of water pushed her car for more than a block. Her roommate, who also works at the restaurant, lost her car underneath a collapsed building.
"We're now jobless, car-less and possibly homeless," said Hughes, who was rescued by boat from the restaurant.
At least five people died in the storm. Two of them died in a creek in Richmond. In nearby Chesterfield County, rescuers pulled a woman's body from a submerged car Tuesday. Two other deaths occurred in Hanover County north of the city.
About 51,000 customers of Dominion Virginia Power had no electricity Tuesday, mostly in the Richmond area. A brick substation that fed the Shockoe Bottom area disintegrated, and utility officials did not know when they would be able to return power to the district's estimated 13,600 homes and businesses.
CSX Corp. shut down passenger and freight traffic through Richmond because the railroad tracks were under water. Many roads remained closed by high water.
A thin layer of mud covered desks and office equipment at the headquarters of American Health Care, which owns 17 nursing homes in Virginia. In one room, the floor gave way, and furniture and office equipment crashed into the basement. A water mark was visible 4½ feet high on the wall.
"I was the last to leave last night at about 6:30, and I looked outside and there was a man in a floating BMW just spinning around right outside the window," said Bill Anderson, an information technology consultant for the company.
Elsewhere, Hurricane Frances grew to a Category 4 storm with 140 mph wind Tuesday as it headed past Puerto Rico on a course that could bring it ashore in hard-hit Florida or somewhere else in the Southeast this weekend, the National Hurricane Center said. A hurricane warning was issued for the southeastern Bahamas.