After days of maintaining tropical-storm level winds, Isaac strengthened Tuesday into to Category 1 hurricane.

The U.S. National Hurricane center says the hurricane is just 15 miles south-southwest of the mouth of the Mississippi River and is moving northwest near 8 mph.

The hurricane's maximum sustained winds are near 80 mph.

Louisiana authorities have closed the floodgates surrounding the east bank of Orleans Parish Tuesday to protect the area from Isaac as it approaches landfall. The Times Picayune reported that all 127 perimeter floodgates have been sealed.

Although Isaac's approach on the eve of the Katrina anniversary invited obvious comparisons, the storm is nowhere near as powerful as Katrina was when it struck on Aug. 29, 2005. Katrina at one point reached Category 5 status with winds of more than 157 mph, and made landfall as a Category 3 storm.

Federal officials said the updated levees around New Orleans are equipped to handle storms stronger than Isaac.

"It's like comparing apples and oranges," Garret Graves, the chairman of the Louisiana Coastal Protection and Restoration Authority told The Times-Picayune. "Unfortunately, there were some very painful lessons learned in Katrina."

The Times-Picayune reported that New Orleans is protected by a $14.5 billion Hurricane and Storm Damage RIsh Reduction System, which consists of higher and stronger levees, walls, floodgates and pumps designed to withstand a Category 3 storm. Isaac, forecasters say, will likely not grow stronger than a Category 2 hurricane.

Forecasters at the National Hurricane Center warned that Isaac, especially if it strikes at high tide, could cause storm surges of up to 12 feet along the coasts of southeast Louisiana and Mississippi and up to 6 feet as far away as the Florida Panhandle.

The Coast Guard has been securing ships and barges in the hurricane’s projected path for days, Admiral Roy Nash, who oversees command from Florida to Texas, told FoxNews.com. He said whenever there’s a storm risk, the Coast Guard does not take any chances.

"It's a collaborative effort with the maritime community," he said. "If the ship is seaworthy, we may send it out to sea; others, we may move them up the Mississippi."

The Coast Guard was searching the Gulf of Mexico near the Florida-Alabama state line Tuesday for a man who failed to return home from a water-scooter trip as Isaac was approaching the coast. The search began after the man's wife called the Pensacola, Fla., station about 8:45 p.m. Monday, Chief Petty Officer Bobby Nash says.

States of emergency were in effect in Louisiana, Mississippi, Alabama and Florida. No flights were scheduled Tuesday, the Louis Armstrong New Orleans International Airport said.

"I don't really trust the levees," said Robert Washington, who planned to evacuate along with his wife and five children. "I don't want to take that chance. I saw how it looked after Katrina back here."

Most residents told Fox News that they have faith in the newly installed levee system.

Many residents and business owners have left the city, but some are boarding up their homes and are making runs to Home Depot, Walmart and gas stations.

President Obama held a press conference Tuesday and said FEMA has been on the ground in Louisiana, Mississippi and Alabama for more than a week. Response teams, he says, are in place to assist any area affected by the storm.

"We're dealing with a big storm," he said. "And there could be significant flooding across a wide area. Now is not the time to tempt fate."

In The Big Easy on Monday, Mayor Mitch Landrieu did not activate a mandatory evacuation. Instead, officials urged residents to hunker down and make do with the supplies they had.

Ky Luu, the head of Disaster Resilience Leadership Academy at Tulane University, said he was impressed by the preparations people were making around the city and the way the authorities informed the public.

"I didn't sense at all any panic," Luu said. "People were methodical and diligent about preparing for this upcoming storm."

Louisiana State University, Southern, Southeastern Louisiana University and Baton Rouge Community College announced they will be closed Tuesday and Wednesday, The Advocate reported.

Landrieu, who will update the city’s latest storm preparations during a press conference at 12 p.m. local time, urged residents to brace for severe dispute no mandatory evacuation order.

"We have a plan in place to secure the City, and we have a plan to respond quickly in the event of emergencies," Landrieu said in a statement. "We're confident that the work we’ve done in the last few years makes us fully capable of handling this type of storm."

Landrieu strongly advised that residents outside of the city's levee protection system or in low-lying areas like Venetian Isles or Irish Bayou to get to higher ground. Residents inside the levee system should take shelter with necessary supplies, including food, water and medications, he said.

"Now is the time to take every precaution that you have been prepared to take over the past few years because that will determine our success in getting through this event," Landrieu’s statement continued. "Stay calm, take this seriously and execute your plans."

Four shelters have been added to serve the city’s homeless population and all public safety agencies will remain operational, Landrieu said. The city’s police department has also announced it will ticket motorists who drive faster than 5 mph on streets with standing water.

Farther away on the Alabama coast, Isaac had begun pelting the shore with intermittent downpours Tuesday morning -- one moment it was dry, and the next brought rain blowing sideways in a strong breeze. Gov. Robert Bentley lifted mandatory evacuation orders for low-lying coastal areas but encouraged residents to remain vigilant nonetheless.

The boardwalk at the tourist town of Gulf Shores was virtually deserted except for John McCombs, who ventured out to see waves lapping at the seawall at the public beach.

Within moments he was drenched and running for cover as a band of rain hit the wooden walkway.

"That's it. It's here," he said, scurrying back across the street.

One question haunting locals is how much oil left over from the Gulf oil spill in 2010 might wind up on the beaches because of Isaac. Experts believe large tar mats lie submerged just off the coast, but no one knows where they are or how many might be in the Gulf.

In Mississippi, beachfront casinos were shutting down late Tuesday morning as a beach road flooded and residents hurried to shelters. Coastal residents Charlotte Timmons and Brenda Batey said they planned to stay put unless Isaac took a more menacing turn, believing it wouldn't cause the devastation of some past storms.

Since Katrina, people have a more cautious attitude toward tropical weather, perhaps so cautious that there's a danger of complacency setting in after near misses, Timmons said.

"It's like crying wolf," said Timmons, a 63-year-old retired media manager. "If they make such a big deal and start moving people out (too soon) and then it fizzles, people might not leave the next time."

Fox News’ Jonathan Serrie, Elizabeth Prann, Edmund DeMarche, Joshua Rhett Miller and The Associated Press contributed to this report.

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