(CNN) The sprawling and soaked Houston metro area and other deluged towns in southeast Texas braced for devastating floods and pummeling rainfall on Sunday as Tropical Storm Harvey stalled over land and drenched dogged searchers and anxious residents.

A flash flood emergency was in effect for parts of the Houston area. National Weather Service and local officials are advising Houston-area residents to avoid traveling.

Three to 4 inches of rainfall were reported in the region in one hour's time. First responders investigated the report of a woman swept away in her vehicle by floodwaters.

"Stay put," the National Weather Service said.

"It's going to last four to five days," said Houston Mayor Sylvester Turner, who urged drivers to stay off the road. "This is Day One."

Hard-hit Rockport

Texans who rode out the most powerful hurricane to hit the United States in a decade ventured out on Saturday to see what was left of their neighborhoods in what was "now turning into a deadly inland event."

The first fatality was reported in the hard-hit coastal city of Rockport, where the person died in a house fire during the storm, Aransas County Judge Burt Mills said Saturday afternoon. "We didn't know about it until today," he said.

At least a dozen people were injured, Mills said.

With dire warnings of tornadoes, torrential downpours and days of flooding to come, broad swaths of southeast Texas were littered with uprooted trees, toppled signs, flagpoles that snapped like toothpicks and clusters of bricks peeled like scabs from walls and rooftops.

Additional fatalities were feared in Rockport, where an estimated 5,000 residents had stayed put for the storm that blasted ashore as a Category 4 around 11 p.m. ET Friday between Port Aransas and Port O'Connor, Aransas County Sheriff Bill Mills said.

A damaged home sits amid a flood on Saturday after Hurricane Harvey slammed Rockport, Texas.

Callers to the local emergency dispatch line told of walls and roofs collapsing on people across the city, where an official had warned those who opted to stick out the storm to write their Social Security numbers on their arms for body identification.

CNN meteorologist and severe weather expert Chad Myers warned residents of Houston to move to higher ground.

"The storm isn't moving, but the rain bands are moving like a pinwheel," he said. "You are going to get a pinwheel (Saturday night) that will wake up -- or you'll wake up with 12-18 inches of new rainfall on the ground."

Rockport home sliced in half from Hurricane Harvey.

Shortly after Harvey became a tropical storm, with sustained winds of 70 mph, Saturday afternoon, Gov. Greg Abbott told reporters that the state had more than 1,000 workers involved in search and rescue operations.

"There's been widespread devastation," Rockport Mayor Charles Wax told CNN late Saturday morning. He said emergency workers were going house to house to check on residents and assess damage.

"We've already taken a severe blow from the storm, but we're anticipating another one when the flooding comes," he said.

Photos: Hurricane Harvey slams Texas Photos: Hurricane Harvey slams Texas Downtown Houston is seen behind the flooded Buffalo Bayou a few days after Hurricane Harvey came ashore in August 2017. The Category 4 storm caused historic flooding. It set a record for the most rainfall from a tropical cyclone in the continental United States, with 51 inches of rain recorded in areas of Texas. An estimated 27 trillion gallons of water fell over Texas and Louisiana during a six-day period. Hide Caption 1 of 22 Photos: Hurricane Harvey slams Texas NASA astronaut Jack Fischer photographed Hurricane Harvey from the International Space Station. Hide Caption 2 of 22 Photos: Hurricane Harvey slams Texas Steve Culver comforts his dog Otis in the hurricane aftermath. Harvey destroyed most of his home in Rockport while he and his wife were there. Hide Caption 3 of 22 Photos: Hurricane Harvey slams Texas Houston police officer Daryl Hudeck carries Catherine Pham and her 13-month-old son, Aiden, after rescuing them from floodwaters. Hide Caption 4 of 22 Photos: Hurricane Harvey slams Texas A damaged home is seen in the Key Allegro neighborhood of Rockport. Hide Caption 5 of 22 Photos: Hurricane Harvey slams Texas A car is submerged by floodwaters on a freeway near downtown Houston. Hide Caption 6 of 22 Photos: Hurricane Harvey slams Texas Melani Zurawski cries while inspecting her home in Port Aransas, Texas. Hide Caption 7 of 22 Photos: Hurricane Harvey slams Texas A graveyard is flooded in Pearland, Texas. Hide Caption 8 of 22 Photos: Hurricane Harvey slams Texas Soldiers with the National Guard patrol Rockport, looking for residents trapped in their homes. Hide Caption 9 of 22 Photos: Hurricane Harvey slams Texas Evacuees are loaded onto a truck in Houston. Hide Caption 10 of 22 Photos: Hurricane Harvey slams Texas People push a stalled pickup through a flooded street in Houston. Hide Caption 11 of 22 Photos: Hurricane Harvey slams Texas Rockport residents return to their destroyed home. Hide Caption 12 of 22 Photos: Hurricane Harvey slams Texas Rescue boats fill Tidwell Road in Houston as they help flood victims evacuate the area. Hide Caption 13 of 22 Photos: Hurricane Harvey slams Texas People wait to be rescued from their flooded home in Houston. Hide Caption 14 of 22 Photos: Hurricane Harvey slams Texas Volunteers in Dallas organize items donated for hurricane victims. Hide Caption 15 of 22 Photos: Hurricane Harvey slams Texas When Harvey slammed the Texas coast and flooded much of Houston, volunteers sprang into action. Some came from as far away as the Florida Everglades, boats in tow, ready to rescue people trapped in their homes. Hide Caption 16 of 22 Photos: Hurricane Harvey slams Texas Larry Koser Jr. and his son Matthew look for important papers and heirlooms inside a flooded home in Houston. Hide Caption 17 of 22 Photos: Hurricane Harvey slams Texas Members of the National Guard rest at a furniture store in Richmond, Texas. Hide Caption 18 of 22 Photos: Hurricane Harvey slams Texas Volunteer rescue workers help a woman from her flooded home in Port Arthur, Texas. Hide Caption 19 of 22 Photos: Hurricane Harvey slams Texas This aerial photo shows flooded residential neighborhoods in Houston. Hide Caption 20 of 22 Photos: Hurricane Harvey slams Texas Tammy Dominguez and her husband, Christopher, sleep on cots at the George R. Brown Convention Center, where thousands of people were taking shelter in Houston. Hide Caption 21 of 22 Photos: Hurricane Harvey slams Texas An elderly patient waits to be rescued from the Gulf Health Care Center in Port Arthur. The facility was evacuated with the help of first responders and volunteers. Hide Caption 22 of 22

The storm was a Category 1 by late Saturday morning, packing winds of 75 mph before Harvey stalled during the afternoon. Some places even far inland were predicted to get as much as 40 inches of rain through Wednesday.

While the worst of the storm surge had ended by midday Saturday, the coastal flooding threat was due to increase as already-swollen rivers and bayous get pounded with heavy rain, CNN meteorologist Michael Guy said. Sea water pushed onto the shore also won't recede quickly, he said, meaning "this is going to be a long, ongoing flood event."

Abbott said the 210-mile-long corridor between Corpus Christi and Houston was expected to receive as much as 30 more inches of rain on top of the double-digit rainfall figures that had already fallen.

#Harvey made landfall at 10 PM CDT as a category 4 hurricane near Rockport, Texas, with max winds of 130 mph and min pressure of 938 mb. pic.twitter.com/98y5wpKmBw — NHC Atlantic Ops (@NHC_Atlantic) August 26, 2017

Harvey wielded the "highest potential to kill the most amount of people and cause the most amount of damage," Brock Long, director of the Federal Emergency Management Agency, had warned. He echoed forecasters who predicted Harvey would be leave areas "uninhabitable for weeks or months," echoing language last seen ahead of Hurricane Katrina in 2005

Here's where we stand:

Latest developments

-- Even after weakening upon landfall, Harvey was still a dangerous storm and "turning into a deadly inland event," the FEMA chief tweeted

-- Harvey could maintain tropical storm strength through late Sunday, then weaken into a tropical depression that hangs in the region through Thursday, the National Hurricane Center predicted.

-- Parts of southeastern Texas remained under a flash flood watch through Tuesday evening, the National Weather Service office in Houston said.

-- More than 300,000 customers on the Texas Gulf Coast had no power around 2 p.m. ET Saturday, the Electric Reliability Council of Texas said, amid reports of downed power lines and trees.

-- There were more than a dozen tornadoes spawned by the storm hit Texas on Saturday. The Houston office of the National Weather Service reported 12 twisters in its area. Harris County Sheriff Ed Gonzalez said deputies saw a possible tornado near Cypress Fairbanks, just outside Houston. There were no immediate reports of injuries. "We're seeing extensive damage to properties," he said.

-- Structural and building problems were reported in Rockport, Aransas Pass, and Port Aransas, Texas, said Tom Beal, a meteorologist with National Weather Service office in Corpus Christi.

-- Corpus Christi officials tweeted Saturday afternoon that evacuees could return "but be advised we are under a water boil advisory & limited wastewater usage due to outages at treatment plants."

-- Coast Guard helicopters rescued 15 people aboard three vessels in distress near Port Aransas on Saturday, according to Capt. Tony Hahn, commander of Coast Guard Sector Corpus Christi.

-- About 25% of oil and gas production in the Gulf of Mexico has been halted because of Hurricane Harvey, the Bureau of Safety and Environmental Enforcement announced Saturday evening.

-- President Donald Trump tweeted early Saturday that he's "closely monitoring" Harvey from Camp David, Maryland. Trump, who plans to visit the storm zone next week, has signed a disaster declaration for Texas.

Closely monitoring #HurricaneHarvey from Camp David. We are leaving nothing to chance. City, State and Federal Govs. working great together! — Donald J. Trump (@realDonaldTrump) August 26, 2017

Damage assessments underway

Firefighters who hunkered down in their station in Rockport as Harvey passed over the city of about 10,000 residents recounted a harrowing night.

The wind was "howling," said Roy Laird, assistant chief of the city's volunteer fire department. "We had probably 140-mph winds earlier."

For hours, Karl Hattman and his family listened to "what sounded like a freight train" roar outside their Rockport home. When the fury calmed, they headed out into the darkness to find many trees down, debris blocking their driveway and Hattman's vehicle damaged by flying roof tiles.

"It's my last one to ride out, I'll tell you that," Rockport resident tells CNN of staying during #HurricaneHarvey https://t.co/TT8xVqveD9 — CNN (@CNN) August 26, 2017

James Salazar is the captain of the volunteer fire department in Seadrift, Texas.

He rode out the storm and drove around Saturday to check on other residents. Salazar said he had some roof damage at his house, but it was not too bad. He said damage to the town could have been worse.

"As far as homes go, there are some with damage and some that are flooded. It could have been much worse," he said.

Taking shelter and bracing for rain

Reminder: Flash Flood Watch is in effect for SE TX this morning through Tuesday evening. 15 to 30 inch totals and with max 40 possible! pic.twitter.com/nmveAQIbT0 — NWS Houston (@NWSHouston) August 26, 2017

"This thing is turning into quite the marathon," Nick Gignac, of Corpus Christi, told CNN around 2 a.m. ET. "You expect these things to be a quicker flash-and-bang than they are. To be honest, the intensity still hasn't let up as the storm came in. Things were a little lighter than they are right now, and you expect it to get intense and let up. And things have not let up at all."

In San Antonio, about 950 people took refuge in shelters, Woody Woodward, a spokesman for the city fire department, told CNN, adding that there was still plenty of space for more people.

Ten critically ill babies in Corpus Christi were taken to a hospital in North Texas ahead of the storm, the Cook Children's Hospital in Fort Worth said in a statement.

"All our babies made it here safely," Dawn Lindley, a registered nurse with Children's Health Transport Team, told CNN. "The majority ... were premature and had ongoing issues. They were easily accommodated to the hospitals here to make sure they had continued care and the storm wasn't going to be a factor in how they recovered from their illnesses."