HOUSTON: Floodwaters reached the rooflines of single-story homes Monday and people could be heard pleading for help from inside as Harvey poured rain on the Houston area for a fourth consecutive day after a chaotic weekend of rising water and rescues.

The nation’s fourth-largest city was still mostly paralyzed by one of the largest downpours in U.S. history. And there was no relief in sight from the storm that spun into Texas as a Category 4 hurricane, then parked over the Gulf Coast. With nearly 2 more feet of rain expected on top of the 30-plus inches in some places, authorities worried that the worst might be yet to come.

Harvey has been blamed for at least three confirmed deaths, including a woman killed Monday in the town of Porter, northeast of Houston, when a large oak tree dislodged by heavy rains toppled onto her trailer home.

A Houston television station reported Monday that six family members were believed to have drowned when their van was swept away by floodwaters. The KHOU report was attributed to three family members the station did not identify. No bodies have been recovered.

Police Chief Art Acevedo told the Associated Press that he had no information about the report but said that he’s “really worried about how many bodies we’re going to find.”

According to the station, four children and their grandparents were feared dead after the van hit high water Sunday when crossing a bridge in the Greens Bayou area.

The disaster unfolded on an epic scale in one of America’s most sprawling metropolitan centers. The Houston metro area covers about 10,000 square miles, an area slightly bigger than New Jersey. It’s crisscrossed by about 1,700 miles of channels, creeks and bayous that drain into the Gulf of Mexico, about 50 miles to the southeast from downtown.

The storm was generating an amount of rain that would normally be seen only once in more than 1,000 years, said Edmond Russo, a deputy district engineer for the U.S. Army Corps of Engineers, which was concerned that floodwater would spill around two 70-year-old reservoir dams that protect downtown Houston.

The flooding was so widespread that the levels of city waterways have either equaled or surpassed those of Tropical Storm Allison from 2001, and no major highway has been spared some overflow.

The city’s normally bustling business district was virtually deserted Monday, with emergency vehicles making up most of the traffic.

Meanwhile, rescuers continued plucking people from the floodwaters — at least 2,000 so far, according to Acevedo, with many more still awaiting rescue.

Chris Thorn was among the many volunteers still helping with the mass evacuation that began Sunday. He drove with a buddy from the Dallas area with their flat-bottom hunting boat to pull strangers out of the water.

“I couldn’t sit at home and watch it on TV and do nothing since I have a boat and all the tools to help,” he said.

They got to Spring, Texas, where Cypress Creek had breached Interstate 45 and went to work, helping people out of a gated community near the creek.

“It’s never flooded here,” resident Lane Cross said from the front of Thorn’s boat, holding his brown dog, Max. “I don’t even have flood insurance.”

A mandatory evacuation was ordered for the low-lying Houston suburb of Dickinson, home to 20,000. Police cited the city’s fragile infrastructure in the floods, limited working utilities and concern about the weather forecast.

In Houston, questions continued to swirl about why the mayor did not issue a similar evacuation order.

Mayor Sylvester Turner has defended the decision and did so again Monday, insisting that a mass evacuation of millions of people by car was a greater risk than enduring the storm.

“Both the county judge and I sat down together and decided that we were not in direct path of the storm, of the hurricane, and the safest thing to do was for people to stay put, make the necessary preparations. … Can you imagine if millions of people had left the city of Houston and then tried to come back in right now?”

The Red Cross set up the George R. Brown Convention Center and other venues as shelters. The center, which was also used to house Hurricane Katrina refugees from New Orleans in 2005, can accommodate roughly 5,000 people.

In the Cypress Forest Estates neighborhood in northern Harris County, people called for help from inside homes as water from a nearby creek rose to the same level as their eaves. A steady procession of rescue boats floated into the area.

Harvey increased slightly in strength Monday as it drifted back over the warm Gulf of Mexico, according to the National Hurricane Center.

Forecasters expect the system to stay over water with 45 mph winds for 36 hours and then head back inland east of Houston sometime Wednesday. The system will then head north and lose its tropical strength.

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