HOUSTON - US President Donald Trump planned to visit Texas on Tuesday to survey the response to devastating Tropical Storm Harvey, the first major natural disaster of his White House tenure.

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.

It had also roiled energy markets and wrought damage estimated to be in the billions of dollars, with rebuilding likely to last beyond Trump's current four-year term in office.

"My administration is coordinating closely with state and local authorities in Texas and Louisiana to save lives, and we thank our first responders and all of those involved in their efforts," Trump told reporters at the White House on Monday.

Trump was scheduled to arrive on Tuesday morning in Corpus Christi, near where Harvey came ashore on Friday as the most powerful hurricane to strike Texas in more than 50 years. The president will later go to the Texas capital Austin to meet state officials, receive briefings and tour the emergency operation center, the White House said.

Flood damage in Texas from Hurricane Harvey may equal that from Katrina, one of the costliest natural disasters in U.S. history, an insurance research group said on Sunday.

In Texas, thousands of National Guard troops, police officers, rescue workers and civilians raced in helicopters, boats and high-water trucks to rescue the thousands stranded in the flooding, which transformed streets into rivers and caused chest-high water buildups in scores of neighborhoods.

In Cypress, Texas, Kayla Harvey, 26, was monitoring Facebook, finding where people were stuck and organizing friends with boats to go out and help. "This is just what we do for our community. We don't wait for someone to come and help we just go out and do it," she said.

Among those feared dead were six members of a family whose van sank into Greens Bayou on Houston's east side.

Virginia Saldivar told The Associated Press that her brother-in-law, Samuel Saldivar, was driving the van on Sunday, trying to deliver his parents and her four grandchildren to safety. He told her that he was crossing a bridge when a strong current in the floodwaters took the van.

It pitched forward over the bridge into a bayou. Saldivar was able to climb out of a window and urged the children, siblings aged 6 to 16, to escape through the back door, but they couldn't.

Houston emergency officials couldn't confirm the deaths.

Harvey was expected to produce another 18 to 33 centimeters of rain through Thursday over parts of the upper Texas coast into southwestern Louisiana, the National Weather Service said.

The Federal Emergency Management Agency director, Brock Long, estimated that 30,000 people would eventually be housed temporarily in shelters.

Reuters - Ap