NEW ORLEANS (CNN)—It’s been four years since Hurricane Katrina wreaked havoc on the southern United States.

The storm nearly drowned New Orleans and swamped the Mississippi Gulf Coast.

But, with hundreds of miles of levees and 58 million cubic yards of dirt still needed to fortify them, many wonder if the next hurricane will be even more devastating.

In New Orleans, there is water everywhere: canals, rivers, lakes. It can be beautiful.

After the storm, everyone here knows that in a heartbeat, that water can turn into a monster.

“I don’t feel that I’ll ever feel as safe as I did pre-Katrina,” said Gwen Adams, a teacher in New Olreans.

Gwen and Henry Adams lived their entire lives in the Lower Ninth Ward.

It was only about 50 yards from a flood wall that broke.

The storm wiped them out and killed their neighbor.

And yet, as hard as it is to believe, they’re rebuilding in exactly the same place and moving back.

“Do people ask you, ‘why are you moving back to the area that’s so close to the levees?'” asked reporter Sean Callebs.

“People ask us that all the time. And I’ll tell them, like I’ll tell you– because it’s my home,” replied Gwen.

In the four years since the storm, the Army Corps of Engineers has spent three billion dollars to repair and upgrade levees and install other storm protection.

By 2013, four years from now, the Corps says it will have spent more than 14 billion.

Colonel Robert Sinkler runs the corps’ project here.

“I am not going to say that folks here will have nothing to worry about, but we are reducing hurricane risks,” said Col. Sinkler. “And there’s always the risk of a bigger, larger bigger storm.”

The Corps of Engineers insists New Orleans has never been safer.

The work going on here is scheduled to be done in 2011 and designed to provide 100 year storm surge protection.

That means each year, there’s a one in 100 chance this system could be put to the ultimate test.

One man, Ivor Van Heerden, is a long time critic of the Army Corps of Engineers and its safety claims regarding New Orleans. He’s the director of Hurricane Public Health at Louisiana State University

If you ask him, “Is the city safer?” and you get a definite a yes and no.

“What is better, is that where it broke, it is being fixed,” said Van Heerden. “But, there are still some old weak spots in the system. So, a category two on the right track, slow moving, could flood parts of the city. Another Katrina would definitely put water all over the levees in many different locations.”

As he took Callebs to a place to show him what he’s talking about, Van Heerden tells us he’s losing his job.

LSU is eliminating his position.

He says it’s punishment for speaking out.

LSU said it can’t comment on personnel matters.

“Before Katrina we were saying, ‘Get out with a category two or above.’ We haven’t changed that message. Get out. It still, in simplicity, is unsafe,” said Van Heerden.

This is the weakest, of the weak links surrounding New Orleans.

The Mississippi River gulf outlet, or Mr.GO, is the weakest of weak links surrounding New Orleans.  It was built by the army corps of engineers about a half-century ago to provide a shorter route for ships from the Gulf Of Mexico to New Orleans port.

Katrina’s wind forced a wall of water down the waterway.

The city didn’t stand a chance.

Some engineers now say, about 80 percent of the flooding in New Orleans can be traced to Mr. GO.

Many critics blame the Corps. After all, they built it.

That’s one reason the Corps is rushing to close it.

Building a 24-foot wall that spans two-miles and will close the funnel.

“A project like this historically would take decades or over a decade to construct. And we are doing it a few years,” said Col. Sinkler.

The tremendous damage caused when Mr. GO failed also prompted a massive class action lawsuit against the Corps. If the Corps loses, it could cost hundreds of billions of dollars.

Gwen and Henry Adams are plaintiffs in the suit.

“One day you’re a viable human being, working contributing to society. The next day, you’re wondering if you are going to be homeless,” said Gwen.

Water everywhere and about 350 miles of levees, stretching about the distance from Washington D.C. to Boston, but the corps says it’s safer now than ever before.

“I say prove it,” said Gwen. “Because we can’t endure another Katrina. We can’t endure another disaster like that.”

Gwen Adams hopes the rebuilding works, but she’s skeptical. After all, the way she and so many others here see it, the Army Corps built this system in the first place.