Gustav Huffs and Puffs and Hits Bayou

NEW ORLEANS, Sept. 1, 2008— -- Hurricane Gustav may not have been the "mother of all storms" New Orleans Mayor Ray Nagin said he feared it could be, but the more than a million people who evacuated the Gulf Coast were warned this evening not to come back to the region too soon.

"I want to underscore the importance of not rushing back to your homes," Department of Homeland Security Secretary Michael Chertoff said. "You don't want to rush from shelter into a place of danger, whether it is weakness in a levee or power lines that are down or some other hidden vulnerability.

"Please give the authorities the time they need to check to make sure it is safe to come back," he said.

For many of the evacuees, the warning could be unnecessary. As Gustav churned northwards through Louisiana and into Texas, it was expected to bring massive flooding that could make many roads impassible.

Watch "Gustav Storms the Gulf" on a special edition of "20/20" at 10 p.m. ET

Nevertheless, in Baton Rouge there was a noticeable increase in cars out on the roads late today after the storm passed, and many of them were heading east toward New Orleans.

Officials blamed Gustav for at least seven deaths. Four people fleeing the storm were killed when their car struck a tree in Georgia, a couple died when a tree fell on the house where they were staying in Baton Rouge, and another woman died in a traffic accident in Louisiana.

New Orleans' levees, still not fully repaired after Hurricane Katrina three years ago, largely withstood the rising waters caused by the storm, though for a time officials in the southern Louisiana parish of Plaquemines feared a potential breech in a local levee there.

The levee overtopped and threatened to break late in the day. Parish President Billy Nungesser said the Braithwaite Levee could collapse, and urged any remaining residents to leave the area.

But emergency workers piled sandbags against the levee where the breach was feared, and later this evening officials said the danger had passed.

New Orleans was lashed with rain and winds that gusted up to 86 mph, and raised water levels so high along its rebuilt levees that water slopped over with each wave, but by the end of the day, the hurricane had been downgraded from a Category 2 to a Category 1 storm and the waters in New Orleans were receding.

Army Corps of Engineers spokesman Rene Poche said the levees were holding and that he did not expect any surge flooding.

The near miss for New Orleans drew a sigh of relief from city officials as well as the 200,000 city residents who fled.

Beverly Dobbs, who took in eight evacuees at her house in West Monroe, La., said her guests "were so relieved to see the newscast and find out that the storm didn't really hit, like Katrina."

Other New Orleans refugees in West Monroe planned to gather at a church that helped organize their evacuation.

"We're planning a celebration dinner -- we hope -- at the White's Ferry Road Church of Christ," Dobbs said.

Gustav, which was a monstrous Category 4 hurricane as it moved through the Caribbean early in the weekend, was later downgraded to a Category 2 hurricane and turned away from New Orleans in the hours before it made landfall.

Later in the day, the storm weakened even further and became a Category 1 hurricane, although it still clocked sustained winds of 90 mph.

It had plenty of punch, however, when it rumbled ashore about 10 a.m. at the bayou hamlet of Cocodrie, an area sparsely populated by shrimpers and oil rig workers. It packed winds of 110 mph and brought with it the threat of a storm surge as high as 14 feet. Gustav also brought the threat of tornadoes.

Gustav looked to be on a trajectory to create a swath of destruction northwest through Houma, Morgan City and on to Lafayette. The area is largely abandoned, thanks to the evacuation of 2 million people, the largest evacuation in U.S. history.

One woman was killed in a car wreck in Louisiana, and three other individuals with critical health conditions died when they were evacuated.

Louisiana Gov. Bobby Jindal said Gustav is expected to deflate to a tropical storm by tonight. Nevertheless, he said Gustav has left nearly 500,000 people in Louisiana without power.

Jindal said it was still too early to know when evacuees would be able to return home, but added it probably would not happen by Tuesday as initially announced by Nagin.

"It's certainly too, too early to say that it's safe for them to start coming back tomorrow," Jindal said at a press conference at the state's emergency operations center in Baton Rouge. "Tomorrow's too early; we need to let the storm come through.

The governor said 85 percent of south Louisiana gas stations were out of fuel, and the industry cannot move fuel until the winds slow down. He called on President Bush to release fuel from the strategic oil reserve, calling it "absolutely critical."

Entergy, the major utility in Louisiana, reports 500,000 of their 1.2 million customers in Louisiana have lost power, and the number continues to grow. Cleco Corp., which has 273,000 customers in the state, said the number of customers without power was at 50,000 and growing.

In Baton Rouge, 60 miles north of New Orleans, and the state's operating center for first responders, Mayor Kip Holden said two hospitals had lost power, but assured residents the situation was under control.

"This is not a doom and gloom scenario. For residents going through this for the first time, everything is going OK. We are seeing some things that are the same as Katrina, but we are getting through them," Holden said. "A lot of people are dependent on us right now. I assure them we are in control."

Mayor Tim Matte of Morgan City, about 80 miles west of New Orleans, told ABCNews.com that a mandatory evacuation had succeeded in clearing out 75 percent of the population and the city was protected by a 24-foot seawall, with levees surrounding the city.

Matte predicted that the area of Houma, a major supply base for the oil industry, would be hardest hit.