New Orleans Mayor Mitch Landrieu: "We are officially in the fight"

(CBS News) NEW ORLEANS - By lunchtime Tuesday New Orleans got its first taste of Hurricane Isaac, attracting the curious, and demonstrating the first signs of a small army ready to respond. About 680 National Guardsman entered the city, with another 3,500 positioned near and along Louisiana's Gulf coast.

At a press conference New Orleans Mayor Mitch Landreau told residents, "We are officially in the fight and the city of New Orleans is on the front line."

While forecasts showed Isaac hitting as a Category 1 storm, officials were preparing as if it's a Category 5.

For the first time since it was built after Katrina, what locals call the "Great Wall" was closed Tuesday. The two-mile long, 26-foot high barrier is normally kept open. The gates were shut to guard against a storm surge that could flood parts of St. Bernard Parish, New Orleans East, and the Lower Ninth Ward.

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While the city is protected by a newly reinforced, $14.6 billion levee system, much of this region will have to do it the old fashioned way: sweat, sand bags and levee walls made of dirt and grass. They also keep boats nearby in case the levee breaches.

Plaquemines Parish President Billy Nungesser said regardless of Isaac's strength, severe flooding is guaranteed again and a levee failure likely.

"When Katrina came across we were a speed bump for New Orleans. It would've been a lot worse if it hadn't hit Plaquemines Parish first," Nungesser said.

In a shelter in Belle Chase in the upper part of Plaquemines Parish, a hairdresser was working on an evacuee while everyone waited for the storm. It's why some 300 people showed up at the shelter the moment it opened. Jane Smith, 68, and 71-year-old Mary Roberts met as volunteers at a shelter during Katrina 7 years ago. On Tuesday night, they needed help.

Smith said she would never move or evacuate for a storm.

"Up north, people say, 'Call me if you need help,'" Smith said. "But down here, they say, 'I'll be there.'"

WFOR Miami's interactive storm tracker

Government resources have shown up in positions outside the hurricane zones: 1.3 million meals ready to eat; 1.4 million bottles of water and 17,000 carts.

Seven states have put their urban rescue teams on standby just in case.