Then New Orleans residents were told Saturday that the partially repaired levee system may not hold up in a strong storm.
Many residents – who lived through Katrina – are already preparing to evacuate the city if Ernesto heads toward Louisiana.
Bari Landry, who lives in a New Orleans neighborhood that was heavily flooded by Katrina, said that after seeing Ernesto's possible storm tracks she decided to reserve a hotel room in Houston for Thursday through Saturday.
Lisa Alphonso was already packing her family's belongings for a potential evacuation.
"Just in case," Alphonso told CBS News correspondent Cynthia Bowers. "When they say go, we're gone."
Just a few miles south of New Orleans, St. Bernard parish took a direct hit from Katrina. One year later, few of houses are habitable, and as many as 14,000 people are still in government trailers — trailers that won't withstand any real wind.
"It would be almost a death sentence if they decide to stay in those locations with the approach of a Category 2 or 3 storm," Jack Stephens, St. Bernard parish's sheriff told Bowers.
Despite aggressive efforts to repair the system following the destruction of Hurricane Katrina, the head of the Army Corps of Engineers conceded Saturday that it isn't clear yet whether it could withstand a hurricane with a heavy storm surge this year.
Lt. Gen. Carl Strock said the agency was carefully tracking Tropical Storm Ernesto, which was in the Caribbean and projected to reach hurricane strength Tuesday. It was on track to enter the Gulf of Mexico, but it too early to tell whether it would strike the southern United States.
Strock was confident the Corps had done all it could to repair and reinforce 220 miles of levee walls, but he said many variables would determine whether the levees could withstand a major hurricane striking near New Orleans, as Katrina did Aug. 29, 2005.
"To pinpoint it to one thing and say 'yes' or 'no' is very difficult," said Strock.
Much would depend on where the hurricane made landfall, wind speed, rainfall and other factors, he said. The biggest concern would be water levels so high that they could cascade over the levee walls, weakening them to the point of breaching.
There's also concern in New Orleans that a new system of pumps installed in the city could make things worse, instead of better, reports CBS News correspondent Joie Chen.
Just days after Katrina hit, engineers launched an all-out effort to protect the city — an impressive flood-gate and pump- system built in a matter of months.
But it could actually make things worse for some homeowners, said Army Corps of Engineers' Col. Jeff Bedey.
The floodgates, set up at the mouths of three canals, are designed to keep Lake Pontchartrain from surging into the city. While the lake will be contained, new rainwater won't have anywhere to go.
A Corps of Engineers study said if the floodgates are used, up to five feet of water could overwhelm some neighborhoods.
Even worse, tests this week showed the pumps may not be working properly.
Homeowners like Matt McBride didn't know any of this when they began trying to put their homes — and lives — back together.
"I'm constantly questioning my decision to come back," McBride said. "I should have taken the insurance money and ran."
Gov. Kathleen Blanco said state officials were keeping an eye on Ernesto.
"It's critical we make the right call for the right reason," she said, cautioning that they want to ward off the chance of unnecessary evacuations.
Officials of the state, city and 14 parishes planned to talk by conference call, New Orleans Homeland Security chief Terry Ebbert said.
Mandatory evacuation in the parishes below New Orleans would kick in when the storm was 50 hours from the coast, Ebbert said. New Orleans would begin mandatory evacuation at the 40-hour mark.
New Orleans already has buses and trains under contract to evacuate people without the means to leave, he said.
Strock appeared with Blanco and Donald Powell, chairman of President Bush's Gulf Coast rebuilding office, on Saturday at a news conference to show off new protections since Katrina.
However, some of the most substantial work planned on the levee system won't be done for the next couple of years.
Col. Richard Wagenaar, who oversees the New Orleans district of the Corps, said the flood control system, which was breached in three places after Katrina, was equal to or better than it was when Katrina struck, but he said he and his staff had already begun making preparations for Ernesto.
Wagenaar said he would have to weigh all the risks in any decision to close the flood gates. When they are closed, it takes longer to pump rain water out of the city's low-lying areas, creating risks of rain flooding.
Blanco said that although she is not happy with the current strength of the levee system, she believes as much work as possible has been done in the year since Katrina.
"I will feel better when they are fully functional and complete, but it will take time," Blanco said. "We've gotten as far as we could get in one year."