Hurricane Isaac makes landfall in southeastern Louisiana

NEW ORLEANS -- As the Gulf Coast braced for Hurricane Isaac hours before the seventh anniversary of catastrophic Hurricane Katrina, the storm made landfall in southeastern Louisiana on Tuesday evening packing 80-mph winds as the outer bands of hurricane-force winds and storm surge began battering New Orleans.

Landfall came in Plaquemines Parish at 6:45 p.m. southwest of the mouth of the Mississippi River, authorities said. By 7 p.m. in New Orleans, winds bent trees like rubbery posts, rain pelted down, and the waters of Lake Pontchartrain churned large waves ashore.

Isaac, a Category 1 storm, was testing a multibillion-dollar effort to improve and fortify a New Orleans flood-control system that failed spectacularly seven years ago.

As residents fled low-lying areas under mandatory evacaution orders, the U.S. Army Corps of Engineers expressed quiet confidence that its revamped network of levees, flood gates, flood walls and pumping stations would hold the line against a sluggish but massive storm likely to deliver two days of heavy rain and widespread flooding.

“We’re in a hunker-down phase now because the storm could sit over us for a while with a lot of wind and a lot of rain,’’ New Orleans Mayor Mitch Landrieu said at a news conference. “If you’ve stayed, you should be executing your plan, with the food, water and all the things you need if you have to stay home a few days.”

With New Orleans essentially shut down, residents faced a siege of sorts, with threats of tornadoes and power outages in a city that is constantly battling high water. The situation was just as tense along the Mississippi and Alabama coasts, which faced the same dire predictions as New Orleans: storm surges of 6 to 12 feet and rainfall totals up to 20 inches in some areas.

Mandatory evacuation orders were issued in Mississippi’s three coastal counties, where authorities opened shelters and imposed curfews from 7 p.m. to 7 a.m.

Isaac was creeping northward at 8 mph. The slow pace means the storm will probably settle in place after landfall, lashing coastal areas with wind and rain for up to two days, the National Hurricane Center says.

Not only the Gulf Coast but much of the Southeast faces days of dismal, soaking weather. “It’s going to take till the weekend before this gets out of the Southeastern states,’’ Rick Knabb, director of the hurricane center, told reporters in a conference call.