Nagin said that the city was sensitive to property rights issues; as a result, he said, he couldn't force people to leave.
But he and city officials made it clear there would be disincentives for those who stuck around past 8 a.m. today, when the mandatory evacuation and curfew take effect.
Under the curfew rules, anyone caught outside of their homes by police or National Guard troops will be arrested, Police Commissioner Warren Riley said.
Though a hurricane watch was issued for a swath of coast from east of Houston to the Florida-Alabama border, the National Hurricane Center's best guess involved landfall on the flat, marshy Cajun country west of New Orleans.
Many of the parish governments in this and other parts of southern Louisiana called mandatory evacuations Saturday.
In Lafourche Parish to the west, local officials, after speaking to state leaders, were resigned to the fact that their communities would be severely affected no matter where the storm went after Saturday night.
A number of residents, however, told The Times that they were going to ride out the storm at home.
"We understand there will be some portion of the population that's going to stay behind for whatever reason," said Brennan Matherne, spokesman for the parish. "We're going to make it clear to them that this is not a good place to be."
Across southern Louisiana, state and city officials were eager to demonstrate that they were doing a better job preparing for Gustav.
Nowhere was this more apparent than in New Orleans, where the botched response to Katrina altered the political landscape and sparked years of soul-searching on issues as diverse as racism, poverty and the state of the nation's infrastructure.
During Katrina, a number of seriously ill patients died in New Orleans' nursing homes and hospitals after flooding cut them off from the wider world. This time, those patients were being evacuated ahead of the storm.
During Katrina, citywide communications systems failed, and rescuers struggled to coordinate their efforts. Now, Riley said, New Orleans has a reliable backup system in case local radio towers go down.
After Katrina, many residents stayed for fear of abandoning pets, which were initially not allowed on boats and buses.
This time, volunteers registered them at the city's Amtrak station, the central departure point for evacuees. Animals were given paper collar tags that matched the bar codes of wristbands given to their owners, with the promise that they would be reunited with their owners in Shreveport.
New Orleans Fire Capt. Pete Lindblom -- who was directing evacuees at the train station Saturday -- spoke bluntly about the lessons local government learned from Katrina.
"I think everyone was shocked at the inability of the population to take care of themselves," he said. Today, he added, "the local politicians and government have bent over [backward]. They're putting forth as much effort as possible."
The evacuation had some glitches: One transportation contractor failed to deliver buses, and the system for tracking evacuees eventually melted down. But compared with the chaotic Katrina evacuations -- in which families waded and swam to the Superdome or were plucked from rooftops by helicopter teams -- it was a model of undramatic efficiency.
Gov. Jindal said it was likely that the system had helped move 10,000 people out of the city Saturday.
However, demographers estimated that 20,000 more of the city's neediest citizens remained.
Officials said the evacuation plan would continue for those still in town.
Some residents said they weren't going anywhere.
K.C. Kasim, 49, runs a popular 9th Ward gas station and grocery store. He stayed through Katrina, living in an apartment above the store.
He ended up rescuing nearly 30 people in his boat.
For Kasim, a native of Iraq, it was a life-changing experience.
After his neighbors learned about what he did, everything changed: A job that had been somewhat impersonal became something deeper. His customers respected him. They became friends.
"If there was a mayor of this area and he would run, he would win," said Eugene Jeanpierre, 66, a neighbor who sometimes helps out around the store.
On Saturday morning the place was bustling with people trying to get out of town.
Kasim, shielded from the hot sun by a baseball hat, was bagging up gas pumps as they went dry. By 9:30, he was all out.
He said he'd keep the store open for groceries until city officials called the curfew. He would stay through that, however, and stay even when the storm came.
"I'm not scared," he said. "If I'm going to die, I'm going to die."
Times staff writer Richard A. Serrano in Washington contributed to this report.