The resignation of US Federal Emergency Management Agency (FEMA) director Mike Brown has received a broad welcome.
The White House moved quickly to replace Mr Brown, installing a senior agency official with three decades of firefighting experience as acting director.
House Democratic Leader Nancy Pelosi said: "Michael Brown's departure from Fema is long overdue, and his resignation is the right thing for the country and for the people of the Gulf Coast states."
The resignation came three days after Mr Brown was sent back to headquarters from the Gulf area, where he had been the face of the government's disaster plan.
It also came a little more than a week after Mr Bush, on his first on-the-ground visit to the region after the storm, said: "Brownie, you're doing a heckuva job."
Some of Mr Brown's critics said his decision would put the focus on efforts to manage the aftermath of the disaster, including helping the thousands of people left homeless.
Republican Senate Majority Leader Bill Frist said he was pleased with the leadership now in place in what he described as a government-wide failure in responding to Katrina.
White House spokesman Scott McClellan praised Mr Brown's work but left out any reference to his contribution to the Katrina efforts. "The president appreciates Mike Brown's service . . . Mike has done a lot of great work on a number of hurricanes," he said.
Mr Bush named David Paulison as the acting head of Fema. Mr Paulison, a career firefighter from Miami, has led the US Fire Administration, a division of Fema and the Department of Homeland Security, since December 2001, according to a biography posted on Fema's website.