NATIONAL NEWS (CNN) — The fury of Isaac slammed into Louisiana with strong winds and pounding rain, generating the first real test early Wednesday of flood control systems and emergency services in New Orleans on the seventh anniversary of Hurricane Katrina.
With forecasters warning Isaac was generating dangerous storm surges and flooding from heavy rain, all eyes were on the New Orleans levee system that was rebuilt and reinforced after it failed when Katrina struck in 2005.
Nearly 1,800 people died in Katrina, the majority when levees failed and flooded New Orleans.
"People who went through Katrina are pretty nervous about storms, and large numbers of people have left," Lynn Magnuson, 58, said in a CNN iReport.
Magnuson said the Lower 9th Ward, which was hard hit by Katrina, "is pretty empty right now."
Issac -- with sustained winds of 80 mph -- was churning slowly about 7 mph along the coast of southeast Louisiana, about 70 miles south of New Orleans, the National Hurricane Center said.
"We're in a hunker down phase now, because this storm could be over us for a while with a lot of wind and rain," New Orleans Mayor Mitch Landrieu said.
"Hunker down means hunker down and prepare to ride it out."
Even with more dangerous conditions likely yet to come, the storm already has caused significant surges and flooding in a number of locales, and not just those directly in Isaac's path. Storm surges of 9.9 feet have been reported in Shell Beach, Louisiana, and 6.2 feet in Waveland, Mississippi, according to the hurricane center.
These surges likely will get worse, with forecasters predicting water levels to rise between 6 to 12 feet on the coast in Mississippi and southeastern Louisiana alone.
The worst of the storm was expected to hit New Orleans in the early morning hours Wednesday, though the first to feel its fury was Plaquemines Parish where Isaac first made landfall Tuesday night before moving back out over the water toward the mouth of the Mississippi River.
"We took the brunt of Katrina, and we are doing it again for this one," Parish President Billy Nungesser told CNN.
Strong winds ripped through the parish, knocking down utility and power poles.
At Nungesser's brick house, he said the wind was so strong that "it's pushing rain through the cracks" into the house.
"The light sockets are spraying you with water like you a hose hooked up there," he said.
Isaac, which started as a tropical storm last week in the Atlantic Ocean, has killed nearly two dozen people in Haiti and the Dominican Republic before starting its journey across the Gulf of Mexico.
On Tuesday, Isaac was classified as a Category 1 hurricane. It is significantly weaker than Category 3 Katrina, though forecasters warn it is capable of causing significant flooding.
"There is no evidence of any (water) overtopping (canals)," Landrieu said. "We have full confidence the levees will hold."
Even so, he and other officials were taking no chances.
The mayor tweeted that about 1,000 National Guard troops and more than 2,900 law enforcement officers are in the city ready to address issues related to the storm.
Power had been knocked out to more than 310,000 customers in Louisiana by the storm, while localized street flooding and downed electrical wires were reported across New Orleans, according to the city.
Isaac earlier prompted three airports to close -- in New Orleans; Gulfport-Biloxi, Mississippi; and Mobile, Alabama -- and cancellations of around 1,500 flights, according to airline and airport officials.
Major ports along the Gulf Coast and the Mississippi River from Baton Rouge to its mouth have been closed, according to the Coast Guard.
Amtrak suspended its train service to and from New Orleans on Wednesday because of Isaac.
Business also came to a standstill because of Isaac.
Fifty-two Walmart and Sam's Club stores in Louisiana and nine in Mississippi were shuttered Tuesday, their parent company said.
In Mississippi, more than 1,800 people were staying in 33 shelters located in 16 counties, according to the state's emergency management agency.
Shrimpers in Bayou Le Batre, Alabama, were among those who heeded official warnings and hunkered down.
The Nuclear Regulatory Commission said it was sending additional inspectors to two Louisiana nuclear plants in the storm's path, as power company Entergy planned a "controlled shutdown" of one of them starting Tuesday afternoon.
CNN's Ed Lavandera, Anika Chin, Mike Ahlers, Aaron Cooper and Ed Payne contributed to this report.