HOUSTON—The largest tropical rainstorm to hit the continental U.S. is forcing tens of thousands of Texans from their homes, scattering them across the state and into overflowing evacuation centers as the mounting crisis strains resources and weary residents.

Early Wednesday, Tropical Storm Harvey made its second landfall just west of Cameron, La., the National Hurricane Center said. On Tuesday, it tore through Texas for a fifth straight day, having dumped more than 50 inches of rain on parts of the state in a new record for the contiguous U.S.

Texas officials said 30,000 people could be forced from their homes due to flooding and more than 725,000 people were under a mandatory evacuation order. A convention center equipped to hold 5,000 people was housing over 9,000 evacuees by midday Tuesday.

Houston Mayor Sylvester Turner late Tuesday ordered a curfew from midnight to 5 a.m. local time to help deter crime and keep the streets clear for first responders.

Harvey has been linked to as many as 13 deaths in Texas thus far, including reports from several local authorities. The fatalities include five people confirmed dead by the medical examiner in Harris County. Among those was a veteran Houston police officer who perished as he tried to drive to work. The Pasadena Independent School District also said that a family of six, including four students and two of their great-grandparents, were swept away by the floodwaters.

“I asked my daughter, is this the end of the world?” said 74-year-old Norma Brown, cradling two of her dogs in a Houston evacuation center after fleeing the flood on a neighbor’s boat. While waiting in the rain to get into the George R. Brown Convention Center downtown, Ms. Brown burst into tears, realizing she had likely lost her home in Dickinson, a badly flooded area southeast of the city.

President Donald Trump flew into Texas on Tuesday, meeting with Gov. Greg Abbott in Corpus Christi near where Harvey first made landfall. Mr. Trump praised Mr. Abbott and the state’s response to the storm.

The Pentagon said Tuesday it has identified as many as 30,000 troops to assist in a massive military response, and was awaiting a formal request for assistance from Mr. Abbott. The deployment would be in addition to National Guard units already working in the state.

“Texas is aware of what we’re planning for, and the capabilities that we’re planning,” Maj. Gen. James Witham, commander of the Air National Guard, told reporters at the Pentagon. “Texas just hasn’t asked for them yet.”

Mr. Abbott’s spokesman, John Wittman, said the state was working “hand-in-hand” with the Pentagon and “deployment of additional National Guardsmen will be announced at the appropriate time.”

President Donald Trump praised the response to Tropical Storm Harvey in remarks with Texas Gov. Greg Abbott on Tuesday during a survey of the storm's damage in Corpus Christi. Photo: Getty Images

As Harvey moved offshore Tuesday, the greater Houston area struggled to absorb the floodwaters.

In some areas, 4 feet of water fell in five days, shattering records and straining infrastructure. A bridge over Greens Bayou in Harris County collapsed, the sheriff’s office said. Up to 30% of Harris County has been flooded, a spokeswoman for the Harris County Flood Control District.

Water breached brimming levees and bayous, and officials were forced to release even more water from strained reservoirs into flooded neighborhoods.

Officials said Tuesday evening that the Addicks reservoir had begun overflowing and was causing additional flooding in nearby neighborhoods. The Barker reservoir is expected to overflow later this week.

At least 17,000 people stayed in Red Cross shelters across the Gulf Coast region on Monday night, according to the relief agency.

Joseph Shives and his family are among over 9,000 evacuees from Tropical Storm Harvey that have taken shelter at Houston’s convention center amid the city's flooding. They talk with WSJ about their ordeal and the uncertainty ahead. Photo/Video: Jeff Bush/The Wall Street Journal

By Tuesday morning, the blocks-long convention center had been transformed into a makeshift city, teeming with tired families lugging the last vestiges of their lives before Harvey hit.

By midday, 9,100 people and countless pets called the center home, nearly double its capacity, said MaryJane Mudd, a spokeswoman for the Red Cross.

Mayor Turner said that the city has opened the Toyota Center, home to the Houston Rockets basketball team, to help handle people who need shelter and reduce the population of people sheltering at the George R. Brown Convention Center.

People will still go to the convention center to seek help, the mayor said. The Toyota Center will not be a site for direct entry.

“I want to reduce that population” at the convention center, the mayor said at a press conference. “I don’t want it to become so large it becomes difficult.”

Local and state officials scrambled to coordinate a massive exodus to other Texas cities. Dallas, San Antonio and Austin prepared what they called “mega-shelters” to take in thousands of Houstonians—extending the flood’s impact across the state.

Officials in Brazoria County, south of Houston, said the levee at Columbia Lakes had breached and urged residents to flee the area. In Baytown, nearly 30 miles east of Houston, police urged residents to hang a white towel or sheet out of their window if they were trapped by rising water.

Weather forecasts offered glimpses of hope for the region, as the storm and rain headed eastward. But rescues from high water continued.

Houston Police Chief Art Acevedo said his officers had performed over 3,500 rescues so far and expected to continue with rescue missions for at least two more days before the city shifts to a recovery mode.

Amid reports of rising rivers and dwindling food supplies, some residents risked flight through watery roads.

Garson Li decided it was time to leave Sugar Land after he saw a two-hour line at his local Kroger supermarket. On Monday afternoon, he got into his Honda CR-V and rolled through foot-high water. Passing trucks pushed water over his hood. An hour outside of Houston on a small highway, he felt the water push him toward a ditch.

“My mentality was that if we can’t get out now, we might be in a situation where we run out of water and food,” said Mr. Li, who works as an auditor at an energy company. After five hours on the road, he made it to Austin where his girlfriend lives. “The route I took yesterday, it doesn’t exist anymore,” he said, “I am very lucky.”

Suman Sunkureddi was part of a stream of dazed and drenched evacuees who arrived in Atascocita just outside the city Tuesday, many of them with little or no belongings.

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Mr. Sunkureddi, 26, said he and a couple of friends had ignored warnings and remained at his family’s house near Lake Houston, in large part because his parents didn’t want to leave and because they never expected waters to reach them.

But Monday morning, his family woke up and it was already too flooded to get out. “We fought it, but it kept coming in,” he said of the floodwaters, which pushed past them into the home and rose steadily, driving them to the second floor and eventually up to the third.

After a long wait, a boat came to get them. His family left behind their home, a couple of new cars and everything else. None of it was covered by flood insurance, he said.

“Our houses were built for a century flood,” he said. “That was a 1,000-year flood.”

Mr. Sunkureddi was happy to find a bag of his belongings he had lost track of in the rescue. It was all he had left. He wasn’t sure where he was headed.

Many people like Mr. Sunkureddi ended up at the Houston convention center. By midmorning, thousands lay exhausted on Red Cross cots that jammed the venue floor, crates of stressed, barking dogs scattered among them.

When the cots were filled, people improvised. Two elderly women fashioned beds out of cardboard boxes and slept on the floor. Evacuees draped in garbage bags walked their dogs.

Shelter From the Storm Thousands of Houston-area residents evacuated to shelters as flood conditions persisted. Other Major flooding Minor flooding Open shelters High water along roads Flood gauges

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