HOUSTON — As people throughout this flooded region sought solace in places of worship on Sunday, some of them makeshift, the governor of Texas predicted that Hurricane Harvey’s economic toll would exceed Hurricane Katrina as the federal government’s costliest natural disaster.

“When you look at the number of homes that have been mowed down and destroyed and damaged, this is going to be a huge catastrophe that people need to come to grips with,” the governor, Greg Abbott, said on CNN’s “State of the Union.”

Harvey, Mr. Abbott said, had proven “far larger than Katrina, both geographically and population-wise.” He said he expected the storm’s ultimate cost to exceed the $120 billion that the federal government spent after Katrina devastated the Gulf Coast 12 years ago. In an interview with Fox News, he suggested that Texas could need up to $180 billion in federal aid.

Mr. Abbott’s forecast came as the Trump administration said that it wanted to tie a first burst of relief money to a measure that would raise the federal debt ceiling, probably inflaming a growing fight over the White House’s request for an initial aid package with a price tag approaching $8 billion. A majority of that money would go to the Federal Emergency Management Agency, and would soon be followed by a request for an additional $6.7 billion — initial payments to rebuild after a disaster as widespread as Harvey.

While the debate about Washington’s spending unfolded on Sunday talk shows, Texas was reckoning with the aftermath of the storm that made its first landfall on Aug. 25, ultimately dumping more than 50 inches of rain.

The authorities, who believe Harvey may be to blame for at least 50 deaths in Texas, sought the evacuation of more homes west of downtown Houston on Sunday, while to the east, close to the Louisiana border, the nearly 120,000 residents of Beaumont faced a fourth day without reliable and safe drinking water. The Environmental Protection Agency said on Sunday that more than 200 public water systems in the region were either shut down or under boil-water notices.

And in Crosby, Tex., the remaining six trailers of unstable chemicals at a flood-damaged plant were ignited intentionally on Sunday afternoon, a move that should end the immediate hazard there, officials said. In images posted on Twitter, smoke could be seen rising from the site.