Michael Brown, the former FEMA head who was in charge when Hurricane Katrina struck in 2005, told CNBC on Monday that he believes the economic impact from Hurricane Harvey will exceed that of Katrina.
By many estimates, Katrina caused upward of $150 billion in total economic damage with about of third of that coming from insured losses.
"We have no idea what the number is going to be [for Harvey]. But I think it's going to be much higher than Katrina," when considering the damage from the relatively quick Tropical Storm Allison in southeast Texas in 2001, Brown said on "Squawk Box."
Harvey, by comparison, has been lingering since it made landfall late Friday as a Category 4 storm in Rockport, Texas, before tracking northeast and swamping the Houston area with more than 20 inches of rain.
Many major refineries in the region were closed, sending gasoline futures higher on supply concerns and oil prices lower on worries about less crude being needed for refining.
The heavy rains from what's left of Harvey are expected to continue for several days and rivers are not expected to crest until later this week, so the flooding could get even worse.
Brown, who was in charge of the Federal Emergency Management Agency during the Republican presidency of George W. Bush, praised the current FEMA administrator, Brock Long, as a "great person to have in this position" to respond to the destruction from Harvey.
"[Long] was my representative to the National Hurricane Center when I was the [FEMA] director. He went on to be the emergency manager in Alabama," Brown said. "He's just that low-key, down-to-earth guy that you need in these kinds of high-pressure situations."
At a Monday morning news conference, Long said more than 450,000 people were expected to seek disaster assistance due to Harvey-related flooding. Long was confirmed as President Donald Trump's choice to lead FEMA in June.
Meanwhile, Harvey, the fiercest hurricane to hit the U.S. in 13 years, was being blamed for five deaths. Thousands of high-water rescues were conducted.
Brown told CNBC on Monday that he understands the political perils of instituting mandatory evacuations before storms like Harvey hit, but said Houston officials should have strongly encouraged residents in the path of the storm to leave the area.
In 2005, President Bush, while touring Katrina destruction, infamously praised Brown. "Brownie, you're doing a heck of a job," Bush said at the time. Brown quit his post shortly after that over what was viewed as a mishandling of the federal response to Katrina.