Among things he probably would have done differently, Chertoff told a Senate committee, was that Michael Brown, then director of the Federal Emergency Management Agency, would not have been put in charge of overseeing the relief effort.
Brown, who resigned under pressure shortly after the Aug. 29 storm devastated New Orleans, Louisiana, and much of the Gulf of Mexico coast, has accused Chertoff and officials of President George W. Bush's staff of ignoring his warnings on the day of the storm.
"It is completely correct to say that our logistics capability in Katrina was woefully inadequate. I was astonished to see we didn't have the capability most 21st century corporations have to track the flow of goods and services," Chertoff said, promising remedies by the start of the 2006 hurricane season in June.
Chertoff testified before the Senate Committee on Homeland Security and Governmental Affairs as a separate House of Representatives investigation concluded that thousands of Katrina's victims could have been spared through better planning and faster action.
The Senate committee purposely saved Chertoff for last so he could fill in some blanks, reports CBS News correspondent Sharyl Attkisson, who adds that the panel has used the previous hearings to build a Katrina timeline.
The House report, titled "A Failure of Initiative," was obtained by CBS News correspondent Thalia Assuras. Thefinds fault with Chertoff, for failing to activate a national plan to trigger fast relief, and with Homeland Security, for overseeing a bare-bones and inexperienced emergency response staff, Assuras reports.
Chertoff, one year on the job, acknowledged missteps. He called the storm "one of the most difficult and traumatic experiences of my life."
Just as the House report was drafted largely by members of Bush's Republican Party, both Republicans and Democrats criticized Chertoff during his testimony.
Republican committee Chairwoman Sen. Susan Collins said his agency's performance "must be judged a failure." She called it "late, uncertain and ineffective."
Sen. Joseph Lieberman of Connecticut, the panel's top Democrat, criticized Chertoff for going to Atlanta for a bird flu conference on Aug. 30, the day after the storm roared ashore, instead of rushing to the disaster scene.
"How could you go to bed that night (Aug. 29) not knowing what was going on in New Orleans?" Lieberman asked.
Under Chertoff's oversight, disaster workers "ran around like Keystone Kops, uncertain about what they were supposed to do or uncertain how to do it," Lieberman said.
"When I went to bed, it was my belief ... that actually the storm had not done the worst that could be imagined," Chertoff said.
Collins told Chertoff "I remain perplexed" about his decision to designate Brown to lead the Katrina response. The FEMA director had expressed skepticism about his agency's being put under the Homeland Security Department; traditionally, FEMA has been an independent agency.
Chertoff said there was "no reason to doubt his commitment" at the time.
"If I knew then what I know now about Mr. Brown's agenda, I would have done something different," Chertoff added.
The hearing was disrupted briefly by a member of the audience who loudly heckled Chertoff, apparently about this week's end of a FEMA program that paid for hotel rooms for hundreds of homeless evacuees.
"This is un-American," said the man, as Chertoff sat stoically. "They're being evicted."
Chertoff was subdued throughout the hearing, unlike the combative stance taken by Brown last week.
"There are many lapses that occurred, and I've certainly spent a lot of time personally, probably since last fall, thinking about things that might have been done differently," Chertoff testified.
Sen. Mark Dayton called FEMA's problems "just so dysfunctional, or nonfunctional, it's frightening."
The House investigative report said that, from Bush down to local officials, government agencies did little other than react to the catastrophic storm after the fact, even when faced with early warnings about its deadly potential.
"The preparation for and response to Hurricane Katrina should disturb all Americans," said the 520-page report, written by a Republican-dominated special committee.
"Passivity did the most damage," it said.
Nevertheless, the White House continues to, stating President Bush has full confidence in him and has not considered asking the homeland security secretary to step down after criticism of his performance on Katrina.
"Secretary Chertoff is doing a great job," White House press secretary Scott McClellan said Tuesday, answering a reporter's question about Chertoff. "The president appreciates his strong leadership. He is someone who is committed to doing everything he can to protect the American people and to continuing to take steps to make sure we are better prepared to respond to the threats that we face."