Texas Gov. Greg Abbott said it will cost more than the $120 billion it took to help rebuild New Orleans following Hurricane Katrina to clean up the areas of Texas hit by Hurricane Harvey last week.

Abbott said on CNN's "State of the Union" Sunday the $7.9 billion Congress is going to consider next week is a "down payment" on the federal funding that's going to have to head toward southeastern Texas.

"It will not be," he said when asked if it was enough. "However it's very clear that the president has made it clear, congress is making it clear, this is just a down payment. Let's not compare it to Sandy. Let's compare it to Katrina.

"The population and geographic size is far larger than Katrina and, I think, Sandy combined. We have over 5 million people. It's the swath from Corpus Christi over to Beaumont. It will require even more than was funded for Katrina, which was $120 billion. In addition to that, we are trying to rebuild the state of Texas ourselves."

The storm will likely end up being the most costly recovery from a natural disaster in the nation's history, he said.

"When you consider the magnitude of the size of this storm, it's far larger than Katrina both geographically and population-wise," he said. "When you look at the number of homes mowed down and destroyed, damaged, this is a huge catastrophe. This will take years to overcome in challenge."

Abbott said there are areas where rescues are still taking place, but urged people to return to their homes in places where floodwaters have receded.

But, there is some concern about what exactly is in those waters. More than a dozen Superfund sites — places designated by the Environmental Protection Agency as polluted and in need of special cleanup — have been flooded by the storm.

However, Abbott said Texans should not wait to find out what's in those waters before returning home to clean up.

"What people need to do is just be very cautious in the way they respond. Do things like wear gloves, masks, clothing so your skin is not brushing up against what you're cleaning," he said. "People can go back to their homes and begin the rebuilding process like we have seen across the state of Texas and already, I'm so impressed with the work ethic of our fellow Texans about getting back and rebuilding the process."