Among the lingering images of the aftermath of Hurricane Katrina in 2006, were the people standing on rooftops, waving makeshift banners that read “HELP US” — or forming the words with things they’d salvaged from their homes. With Irene bearing down on the East Coast of the U.S., it’s hard not to wonder if it could happen again.

In 2006, tens of thousands New Orleans residents didn’t evacuate ahead of the storm. Many couldn’t, because of economic circumstances or physical disability (some were in hospitals, and literally couldn’t escape.) The then New Orleans mayor, Ray Nagin, lays blame on a tangle of bureaucracy at the state and federal level in his new, self-published book about the Katrina disaster. But others say Nagin’s administration left dozens of buses idle on the opposite side of town, hampering the ability to get people out.

Click here to view a Grio slideshow of iconic images from Hurricane Katrina

Still, as with all natural disasters, there were some people who simply chose not to go.

With Hurricane Irene bearing down on the East Coast, the talk of potential evacuations, as far north as New York, has begun.

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If Irene becomes another Katrina — God forbid — what will people do this time? And is there an ethnic component to the willingness, or unwillingness, of some to leave when authorities advise that it’s time to go?

Robert Parker, who was director of the Miami-Dade, Florida Police Department (the first African-American to hold the position) from 2004 through 2009, said that when natural disasters strike, those who stay behind fall into three categories: “those who can’t leave, those who won’t leave, and those who are unfortunately misinformed.”

“The reality is that some people cannot leave without the assistance of government,” Parker said. “But in the last few years, government has really stepped up to meet the needs of those who can’t. And that leaves those who will not leave.”

Parker says people who for whatever reason, remain behind despite an evacuation order, whether it’s a hurricane (which typically is the reason for an evacuation in Florida) or another natural disaster, often fall victim to procrastination.

“There’s a certain element of denial,” said Parker, “where they say ‘I’ve lived here all these years and nature hasn’t taken me out. But we’ve seen with natural disasters that nature can.”

Parker said that for law enforcement, which winds up at the forefront of post-disaster relief because police are required to be visible in the aftermath of a storm, the greatest effort and expense comes from rescuing people who could have evacuated but didn’t, and those who failed to prepare for the aftermath of a storm.

In Miami-Dade, “you could spend $1 million a day just to keep the police mobilized for 12 hour shifts” after a disaster, Parker said. “And that’s for everything from public safety, to having to go door to door in a mobile home park, to see if people have evacuated.”

When police find people who have refused to leave, Parker said his officers have given out ID tags, and told people to keep them around their necks, “so people can identify your body later.”

“That tends to hit them like a ton of bricks, because it’s reality setting in,” Parker said. “But short of that, people sometimes wouldn’t budge.”

And while Parker said there’s no evidence that race plays a role in who stays and who evacuates, he said that during his tenure, he did see instances where economic status correlated with a refusal to go, particularly in the low income black communities strewn across Miami-Dade.

Elizabeth Fussell, an associated professor who teaches sociology and demography at the University of Washington, said that it is social networks, not race, that best determines someone’s willingness, or ability, to be evacuated.

“I think it has more to do with access to social networks,” said Fussell, who wrote a paper called “Leaving New Orleans: Social Stratification, Networks, and Hurricane Evacuation” in 2006 when she was teaching at Tulane University in Louisiana. “If your community and the people who you’re actually connected to; If they call you and say, ‘hey this hurricane is coming,’ that’s what matters most in an evacuation. If you’re socially marginalized for whatever reason, if you’re elderly or you live alone — it’s people who are more socially isolated and who don’t have that social network that’s prompting them to leave, and even helping them to leave,” who stay behind.

Fussell pointed out in that June 2006 paper that:

New Orleans is a city in which 27.9 percent of residents live below the poverty line, 11.7 percent are age 65 or older, only 74.7 percent are high school graduates and 27.3 percent of households do not have cars. Furthermore, a larger than average percentage of residents have disabilities: 10.3 percent of 5-20 year olds, 23.6 percent of 21-64 year olds, and 50.1 percent of those age 65 and older have disabilities according to the 2000 U.S. census. In addition, 77.4 percent of New Orleans residents were born in Louisiana and have lived most of their lives there. These statistics alone go far to explain why tens of thousands of the 500,000 residents of New Orleans did not evacuate; in so many ways they were more rooted in place than the average American. The fact that 67.3 percent of the residents are African-American was only the most visually apparent of all these statistics.

Parker agreed that race is not the primary factor holding people back when authorities say it’s time to go.

“I’m always amazed that ever time there’s a major power outage, we have these needless deaths because of people who bring charcoal grills inside the house or the garage to cook, or who buy generators and run them in a closed garage, and then succumb to carbon monoxide poisoning.” Parker said. “That’s not black people, that’s everyone — black, white and otherwise.”

But Parker said that people in the African-American community, who are especially vulnerable in some cases because of their location (as was the case in New Orleans’ Ninth Ward — which sits at the bottom of essentially a basin, which filled with water after Katrina) or because of economics, should be especially vigilant about being prepared.

“People should be prepared to take care of themselves without government assistance in the first three days after a disaster,” Parker said. “And setting up water and food relief stations after a disaster takes an enormous amount of resources.” Parker advises always having three days worth of food (that won’t spoil without refrigeration) and water on hand, just in case a disaster strikes.

He also said that when a storm hits, additional casualties are created by panic, which he said could be reduced by a small amount of prior planning.

In the end, however, Fussell points out that it’s those social networks that reinforce the kinds of behaviors that can save lives in a disaster.

“Without strong social networks,” Fussell said, “people sometimes lack the will and the ability to leave before it’s too late.”