NEW ORLEANS - Isabelle Cossart stopped her tour van next to a group of women planting flowers at the entrance to their storm-ravaged community.

"Isn't that wonderful, their optimism," Cossart said Thursday over a speaker system in the van.

Riders snapped photos as Cossart waved to the women, whose faces soured slightly as they read the sign on the side of the van: www.ToursByIsabelle.com.

Cossart is a pioneer in New Orleans' new thriving industry: disaster tourism.

In a city most famous for its anything-goes revelry and irreverent celebrations, entrepreneurs are cashing in on a natural disaster that left more than 1,000 dead and led to widespread looting and mayhem.

Some storm victims find the tours crass and ghoulish. But Cossart and other operators insist the tours are important in educating the nation about Katrina's devastation and the slow recovery in a city several feet below sea level.

"We need help, and this story needs to be told," said Cossart, who moved from France to the United States to become a school teacher before starting the tour company 30 years ago.

Cossart, who laid off all 22 employees after the storm, has run nearly 40 tours since October, mostly for a trickle of tourists who can find lodging, a few community leaders and a group of Japanese engineers in town to study the damage.

For $49 each, riders get a three-hour tour that begins with a detailed history of the French Quarter and ends at one of New Orleans' new attractions: An enormous red barge that broke through a levee breach and now sits on top a small school bus and several crushed homes in the devastated 9th Ward.

"Oh my God," gasped Neilan Tyree, a 46-year-old business developer from New Orleans on the tour with family visiting from Charlotte, N.C. "I never knew it was this bad."

Neighborhoods that suffered the worst destruction choke with processions of cars carrying camera-wielding passengers from as far as California, New York and Florida.

In the 9th Ward, roads became so jammed near the barge that a Homeland Security officer stood guard Thursday so gravel-filled trucks could get through to repair levees.

Most sightseers sit silently in their cars, snapping pictures, pointing out toppled cars or gutted homes as if on a theme park ride. The more adventurous treat storm-battered homes like free museums, entering houses or yards for an intimate look at nature's fury.

A church group from Athens, Ohio, stepped over debris to get into a large home torn in half by a levee breach in the Lakeview neighborhood, north of downtown.

The teenagers marveled at family pictures that remained on the wall, and a large flat-screen television that sat where the living room had been.

"It makes you really sad," said Diana Kinder, 50, who helped bring the group to New Orleans to volunteer at a local church. "You can't beat experiencing something for yourself."

But the fragile peace between sightseers and storm-battered residents has begun to fray as the trickle of gawkers turns into a flood, and some grow more determined to claim a memento.

"It makes you feel like people are disrespecting our disaster," said Viola Watson, who has recovered little more than a ceramic cat and porcelain eggs from her 9th Ward home destroyed by flood.

The Rev. Gregory Pembo, whose Lakeview neighborhood home flooded, was on his roof a few weeks ago cutting up a fallen oak tree when a tour bus drove past. He was only mildly unnerved until the bus stopped, then backed up so riders could get a better view of the devastation.

For reasons that still surprise him, the normally mild-mannered Pembo started waving the chain saw in the air, gesturing for them to leave.

"All of the sudden, I felt like Jason," he said, referring to the marauding, chain saw-wielding horror movie character. "Sometimes I get a little vexed when people drive by, stop, and start gawking while I am working."

Frustrated residents such as Watson note that tour companies didn't swarm the World Trade Center site after the Sept. 11 terrorist attacks.

"It might be educational, but what about the feelings of the people who are here?" she asked.

Gray Line New Orleans Inc., which laid off all but six of its 65 employees after the storm, is starting its own disaster tours next week that will tout New Orleans' port, seafood industry and role in the national economy. The tours are called: "Hurricane Katrina - America's Greatest Catastrophe."

Gray Line officials are banking that those willing to pay $35 a seat will be so moved by the destruction they will help lobby Congress for more disaster assistance. The company plans to donate $3 from each ticket to storm relief charities.

"You can't help us until you see the devastation," said spokeswoman Julee Pearce, who relocated to Baton Rouge after the storm.

Some sightseers are conflicted about their desire to see the worst of Katrina's wrath.

"I kind of don't like standing here taking pictures, but in a way we are witnesses," said Karen Chauvin, 64, a former New Orleans resident visiting from San Antonio, Texas.

Janice and Joe Warrington drove 12 hours from Brandon to view the devastation in his former hometown.

"It's like when there's a car wreck, you have to come out and see it," Joe Warrington said after he edged his shiny, white BMW through a road clogged with mud and debris.

Richard Erb, a concert trombonist from the uptown area of New Orleans, said the historical knowledge gained outweighs the uneasiness of taking part in the burgeoning disaster spectacle.

"It makes you feel a little ghoulish," said Erb, 69. "But in a way, we need to know what happened because it could happen again."