Experts say the consequences could be far more deadly in the event of a radiological or other terrorist strike.
"The nightmare that we all have is that, God forbid, there's a terrorist attack of some kind on a major American city that requires evacuation without warning," said Sen. Joe Lieberman, D-Conn.
"We need to be better prepared," Lieberman, the top Democrat on the Senate Homeland Security Committee, said on CNN's "Late Edition."
CBS News correspondent Sandra Hughes reports that after the Sept. 11 attacks, President Bush created the National Incident Management System, mandating that every urban area have an emergency management plan. Unfortunately, many cities lack the funds to practice for disaster.
President Bush has ordered the Homeland Security Department to review disaster plans for every major metropolitan area. Experts say the slow pace of evacuations in Houston and New Orleans show the need for changes to get people out of harm's way in a more urgent emergency.
"You have to accept the possibility that a major portion of the people will be left behind," said Roger Cressey, a former anti-terrorism official in the Clinton and Bush administrations. "You may have to write some of them off in far larger numbers than people realize."
Cressey said the answer is not simply giving local governments more money to improve emergency operation plans.
Lawmakers said they plan to address the issue.
"You would think four years after 9/11 with billions of dollars spent to improve our emergency preparedness that the response to Katrina would be far crisper, far better coordinated and not marred by failures at all levels of government," said GOP Sen. Susan Collins of Maine, who heads the Senate Homeland Security Committee.
Cressey said there must be plans in place to move the poor and disadvantaged. Thousands of them were left behind in New Orleans after Katrina.
At least two people have died as a direct result of Rita — a man in Texas hit by a falling tree during the storm and woman in Mississippi killed in a tornado spawned by Rita. And 23 people died during evacuation, when a bus carrying nursing home evacuees caught fire.
Experts said authorities must be prepared to turn two-way streets and highways into one-way evacuation routes with maximum traffic flowing out of the city. Many people fleeing New Orleans and Houston were stuck in traffic jams while the side of the highways leading into the city went virtually unused until the end of the evacuation.
"I think we need to fine-tune the planning so that contra-lanes are open earlier so that all the outgoing traffic can go on both sides of a freeway earlier than was done in Rita," said Sen. Kay Bailey Hutchison, R-Texas.
"I think that will be our added lesson for Rita from Katrina," she said on ABC's "This Week."