(Adds details on record rainfall, breached levee, New Orleans, quotes from mayor)
HOUSTON, Aug 29 (Reuters) - U.S. President Donald Trump headed to Texas on Tuesday to survey the response to devastating Tropical Storm Harvey, the first major natural disaster of his White House tenure, as officials in Houston struggled to manage the record-breaking rains.
The slow-moving storm has brought catastrophic flooding to Texas, killed at least nine people, led to mass evacuations and paralyzed Houston, the fourth most-populous U.S. city. Some 30,000 people were expected to seek emergency shelter as the flooding entered its fourth day.
Officials in Harris County, where Houston is located, said reservoirs built to handle drainage water were beginning to overflow on Tuesday. They urged residents to evacuate as they released water to alleviate pressure on two dams, a move that would add to flooding along the Buffalo Bayou waterway that runs through the area.
Officials in Brazoria County, south of Houston, also called for immediate evacuations around a levee Columbia Lakes that had been breached by Harvey's floodwaters.
Some 3,500 people already have been rescued from high waters in the Houston area with police, firefighters and National Guard troops continuing to try to locate those marooned in high waters.
"Yesterday the focus was on rescue. Today it will continue to be on rescue," Houston Mayor Sylvester Turner told reporters.
The storm broke Texas rainfall records at one measuring site south of Houston, which recorded 49.32 inches (1.25 m) of precipitation since the storm's start. The rainfall is more than the region typically sees in a year and exceeds 48 inches (1.22 m) recorded in 1978.
Multiple looters had been arrested overnight, police said.
Harvey has roiled energy markets and wrought damage estimated to be in the billions of dollars, with rebuilding likely to last beyond Trump's four-year term in office.
TRUMP TO VISIT CORPUS CHRISTI, AUSTIN
Trump was headed first to Corpus Christi, near where Harvey came ashore on Friday as the most powerful hurricane to strike Texas in more than 50 years. He also was going to Austin, the state capital, to meet with officials, but Houston was not on his itinerary because much of it is impassable.
While much of the damage in Houston has been rain-related, the storm's winds picked up overnight, bending street signs and tearing at metal fences in the downtown.
Much of the Houston metropolitan area, where 6.8 million people live, remained underwater on Tuesday. Dangerous rescues went on through the night.
About 9,000 evacuees were staying at Houston's George R. Brown Convention Center and Turner said his office had asked the Federal Emergency Management Agency for assets to allow the city to shelter another 10,000 people.
"I'm just trying to stay strong," said Julio Gamez, 35, who evacuated to the center on Saturday night with his wife after floodwaters rose to within a foot (30 cm) of his roof. "Everything's gone. We've lost everything. But at least we're safe."
Other shelters were set up in Dallas, about 250 miles (402 km) to the north, for about 8,000 people, and Austin, 160 miles (258 km) west, to take in 7,000 people.
Television pastor Joel Osteen's sprawling Lakewood Church offered to accept flood-stranded residents a day after posting on its Facebook page that it was inaccessible due to severe flooding.
After a deluge of angry comments on social media, the church said on Twitter that it would take in people who need shelter.
LOUISIANA ALSO THREATENED
Harvey was expected to reach Louisiana early on Wednesday - one day after the 12th anniversary of Hurricane Katrina hit the state and killed 1,800 people.
New Orleans already has received almost 6 inches (15 cm) of rain from Harvey, Mayor Mitch Landrieu said in a statement. He urged city residents to shelter in place through the storm.
Among the most recent deaths from Harvey was a man who drowned on Monday night while trying to swim across flooded Houston-area roads, the Houston Chronicle quoted the Montgomery County Constable's Office as saying.
The slow-moving storm's center was in the Gulf of Mexico about 113 miles (183 km) southeast of Houston by midday Monday. It was likely to remain just off the coast of Texas through Tuesday night before moving inland over the northwestern Gulf of Mexico on Wednesday, according to the U.S. National Hurricane Center.
Since coming ashore, Harvey has virtually stalled along the Texas coast, picking up warm water from the Gulf of Mexico and dumping torrential rain from San Antonio to Louisiana.
Harvey was expected to produce another 6 to 12 inches (15-30 cm) of rain through Thursday over parts of the upper Texas coast into southwestern Louisiana, the National Weather Service said.
Schools and office buildings were closed throughout the area, with hundreds of roads blocked by high water and the city's two main airports shut.
The Gulf of Mexico is home to half of U.S. refining capacity. The reduction in supply led gasoline futures to hit their highest level in two years this week as Harvey knocked out about 13 percent of total U.S. refining capacity, based on company reports and Reuters estimates.
The floods could destroy as much as $20 billion in insured property, making the storm one of the costliest in history for U.S. insurers, according to Wall Street analysts.
(Additional reporting by Peter Henderson, Gary McWilliams, Ernest Scheyder and Erwin Seba in Houston, Andy Sullivan in Rockport, Texas, Jon Herskovitz in Austin, Steve Holland and Jeff Mason in Washington and David Gaffen in New York; Writing by Scott Malone and Jon Herskovitz; Editing by Chizu Nomiyama and Bill Trott)