COLUMBIA, S.C. — After a week of steady rain, showers tapered off Monday and an inundated South Carolina turned to surveying a road system shredded by historic flooding. And in a cruel twist, thousands of residents faced the prospect of going days without running water.

The governor warned communities downstream, near the low-lying coast, that they may still see rising water and to be prepared for more evacuations. More than 900 people were already staying in shelters and nearly 40,000 people were without water.

At least 11 weather-related deaths in two states were blamed on the vast rainstorm, with one of the latest coming when a motorist drove around a barricade and the sedan stalled in rushing waters. The driver drowned, but a woman who was riding in the car managed to climb on top of it and was rescued by a firefighter who waded into the water.

“She came out the window. How she got on top of the car and stayed there like she did with that water – there’s a good Lord,” Kershaw County Coroner David West said.

On Monday, the rains moved north into North Carolina and the mid-Atlantic states. The rainstorm is part of an unprecedented system that dumped more than a foot of rain across South Carolina and drenched several other states.

Sunday was the wettest day in the history of South Carolina’s capital city, Columbia, according to the National Weather Service.

The 16.6 inches of rain that fell on Gills Creek near downtown Columbia on Sunday was the rainiest day in one single spot in the United States in more than 16 years, among weather stations with more than 50 years of record-keeping.

The last time there was that much rain in one spot on a single day in the United States was Sept. 16, 1999, when 18.3 inches fell on Southport, North Carolina, during Hurricane Floyd.

“The flooding is unprecedented and historical,” said Dr. Marshall Shepherd, a meteorologist and director of the atmospheric sciences program at the University of Georgia.

He said the unique double punch of the upper level low – aided by a “river” of tropical moisture in the atmosphere from Hurricane Joaquin spinning far out in the Atlantic – gave the monster rainstorm its punch.

South Carolina Gov. Nikki Haley has said the deluge is the kind of storm seen only once in 1,000 years.

On Monday, she said 550 roads and bridges were closed across the state. All will have to be checked for structural integrity, which could take weeks or longer.

She said floodwaters will continue to rise in some areas as rainwater runs down the state toward the coast.

“This is not over. Just because the rain stops does not mean that we are out of the woods,” Haley said at a news conference.

Haley, a Republican, also thanked President Obama for a disaster declaration that frees up federal resources and for personally calling her Monday morning.

“He was extremely gracious and kind,” she said.

Haley said that nine people have died in the state since the storm started. Two other weather-related deaths were reported in North Carolina.

At least three people were killed Sunday in South Carolina, including a transportation worker who died overseeing work near downtown Columbia, a woman who was swept away in her SUV and the man who drove around the barricade Sunday night in the Lugoff community northeast of Columbia, the coroner said. McArthur Woods, 56, drowned after his car was inundated.