(CNSNews.com) – Historic flooding, as much as 50 inches of rain, is expected to fall in the Houston area before the remnants of Hurricane Harvey finally move away by mid-week, forecasters say.

The Federal Emergency Management Agency has been there since last week, before the hurricane hit – and it expects to be there for years, not weeks or months:

“FEMA is going to be there for years, sir,” FEMA Director Brock Long told CNN’s “State of the Union” with Jake Tapper on Sunday.

“This disaster is going to be a landmark event. And we’re already in the stages. While we’re focused on response right now and helping Texas, you know, respond, we’re already pushing forward recovery housing teams.

“We’re already pushing forward forces to be on the ground to implement National Flood Insurance Program policies as well, and doing the inspections that we need. So, we’re setting up and gearing up for the next couple of years.”

Long said nearly 5,000 federal government employees are on site in Texas and Louisiana, “supporting all types of operations.”

Aside from search and rescue, “we’re supporting the mass care missions,” Long said. “We expect a huge mass care mission today of people flocking to shelters, if they can get to shelters.”

Long described President Trump as “extremely concerned, incredibly engaged.

Most of Trump’s 15 tweets over the weekend focused on the devastation in Texas.

“HISTORIC rainfall in Houston, and all over Texas. Floods are unprecedented, and more rain coming. Spirit of the people is incredible. Thanks!” Trump tweeted Sunday night.

“Major rescue operations underway!” he said in a second tweet.

The president announced via Twitter on Sunday morning that he was going to a Cabinet meeting via tele-conference to discuss the situation in Texas: “Even experts have said they’ve never seen one like this!” he wrote.

President Trump plans to go to Texas on Tuesday, but there are no details yet on where he’ll stop. From there, he’ll attend a political rally in Missouri.