A recent study reports wind speed plays a major role in people’s minds as they make the decision to stay or go.

By Tom Jacobs

People load their belongings onto a car in Myrtle Beach, South Carolina, as Hurricane Matthew makes its way toward the United States. (Photo: Nicholas Kamm/AFP/Getty Images)

As Hurricane Matthew approaches the east coast of Florida, numerous counties have issued either mandatory evacuation orders or voluntary recommendations to head inland. Who follows such directions, and who doesn’t?

A study published earlier this year produced some surprising answers, including a racial divide. It found whites are less likely than their non-white neighbors to pick up and go, unless and until the warnings get truly dire.

“With regard to disaster response, the debacle of Hurricane Katrina remains salient in the black community,” writes a research team led by psychologist Sarah DeYoung of the University of Georgia.

“There is still a need to spread information to the public that widespread looting in disasters is not as common as the fear of looting.”

The study, in the journal Environmental Hazards, analyzed responses to surveys filled out by 284 people living in hurricane-prone regions of North Carolina: Wilmington, Raleigh, Jacksonville, and the Outer Banks. The surveys were completed by telephone in the winter and spring of 2011.

“Respondents were asked, ‘If the local authorities issued a mandatory evacuation order for a tropical storm, would you actually evacuate?’ The question was repeated 12 times, changing ‘mandatory’ to ‘voluntary,’ and ‘tropical storm’ to ‘category 1, 2, 3, 4, or 5 hurricane.’”

For both mandatory and voluntary orders, non-whites in the study (most of whom were African American) “were significantly more likely to state that they would evacuate for lower-level storms,” the researchers report. The researchers suspect this may reflect lower levels of trust in local authorities.

“Minority residents,” they write, “may evacuate at lower thresholds of storm categories if they feel that there will be insufficient emergency services and support if the hazard is severe.”

Not surprisingly, the researchers also found people who had ridden out previous storms had a higher threshold for agreeing to evacuate. “This suggests that those who ignored orders may have gained more confidence due to their past decision,” they write.

When asked why they would choose not to evacuate, the two reasons most often given were traffic (roads can get jammed when many thousands of people are simultaneously leaving coastal areas) and concern about damage to their property, including looting.

“There is still a need to spread information to the public that widespread looting in disasters is not as common as the fear of looting,” the researchers write.

DeYoung and her colleagues found wind speed was the main factor people used when evaluating how threatening a storm appears, thus greatly affecting the decision to evacuate. They argue this is a fundamental misreading of the threat, “since wind is not usually the main cause of mortality in a hurricane event.”

“Between 2000 and 2010, there were 1,437 deaths attributed to hurricanes in the U.S., most of these from Hurricane Katrina in 2005,” they write. “Drowning was the major cause of directly related deaths (59.7 percent), mostly in evacuation zones where residents had decided not to leave. Twenty of those deaths were drowning within the home.”

So the scary forecasts of sustained winds of 140 mph may save some lives by convincing people who would otherwise be reluctant to evacuate that it really is time to go.