New Orleans ? Mayor Ray Nagin unveiled a new evacuation strategy for New Orleans on Tuesday that relies more on buses and trains and eliminates the Superdome and Convention Center as shelters.

“There will be no shelter of last resort in the event of a major hurricane coming our way,” Nagin declared.

The mayor, facing a runoff election May 20, has been widely criticized for failing to get the city’s most vulnerable residents out of town as Hurricane Katrina approached.

The Superdome and the Convention Center became scenes of misery for days after the Aug. 29 hurricane as thousands of evacuees, many of them ill or elderly, languished with shortages of food and water.

The mayor announced the plan on the same day the American Society of Civil Engineers released a report critical of levee designs in the New Orleans area by the Army Corps of Engineers.

The report found evidence of designs based on outdated land-elevation data, which resulted in miles of levees that did not climb as high above sea level as they were supposed to, often missing the mark by 2 feet or more.

It has long been known that southern Louisiana has problems with sinking land, and the Corps had policies to address changing elevations that were not followed consistently, the report said.

The engineers said they saw “a clear need for a stronger commitment to consistent use of existing policies and procedures than has been the case in the past.”

Nagin said he was confident that repair work on the levees would leave the city more secure than before Katrina.

His new evacuation plan focuses on getting everyone out of the city for hurricanes stronger than Category 2, or those with sustained winds of 111 mph or higher. Katrina is believed to have been a Category 3 or 4 when it hit New Orleans.

In the future, Nagin said, the Convention Center will be a staging point for evacuations, not a shelter.

“There will be a mandatory evacuation, and I would be shocked if people did not abide by it,” Nagin said. “We’re dealing with adults, so if you decide to disobey a mandatory evacuation, you are confining yourself to your home in an emergency.”

Nagin also said federal Homeland Security Secretary Michael Chertoff had cleared the way for the use of Amtrak passenger trains in the event of an evacuation. People with special medical needs and the elderly would be picked up by city, school and church buses and taken to the train station or evacuated by bus to shelters.

The plan also addresses specific problems that arose during Katrina, such as tourists being stranded in hotels and looting.

For security, 3,000 National Guard troops could be stationed with police throughout the city prior to a storm, and a dusk-to-dawn curfew would be in place once the evacuation was over, Police Supt. Warren Riley said.

“It will be an overwhelming force,” Riley said. “When citizens leave, they will have no doubt their property is protected. Obviously, it is far beyond what we have done in the past.”

The storm killed more than 1,300 people in Louisiana and Mississippi. Forecasters are expecting the 2006 Atlantic hurricane season, starting June 1 and running through November, to have at least nine hurricanes, five of them intense.