What did it all mean when we fled Hurricane Irma?

It was slow going as Floridians crept north along I-75 to evacuate before Hurricane Irma hit.
It was slow going as Floridians crept north along I-75 to evacuate before Hurricane Irma hit. abcnews.go.com

Now that the true clean-up in southeast Florida from Hurricane Irma is gathering momentum, it is time to revisit one of the storm’s biggest surprises — mass evacuation — and what it means for the future.

Although the definitive research remains to be done, it seems clear that evacuation from Hurricane Irma in Florida (and out of Florida altogether), reached unexpected levels in the week before the storm’s impact. We still can’t be sure of the percentages of people who evacuated (50 percent compliance is a decent rule of thumb in U.S. evacuations), particularly from coastal Zones A and B, but the absolute numbers of people who took to the roads seemed to take everyone by surprise. Why was this the case?

The first part of the answer is obvious: As we have increased population in coastal and near-coastal areas (and increased density in many urban coastal areas), there are simply more people at risk. The second, and less obvious, factor is that these populations, particularly newcomers, are more affluent than generations past and can more easily afford to evacuate.

I would argue that the third contributing factor, more psychological, derives from the National Hurricane Center’s new product: map-based and highly visual storm surge-flooding estimates and the constant verbal and graphic reminders to, “Hide from wind but run from water.”

We heard repeatedly that you can hunker down in place from a storm’s wind effects but absolutely should flee from a hurricane’s real killers — storm surge and flooding. The impact on us of this new NHC tool was, at least for this season, reinforced by what I saw as a “Harvey Effect,” the fourth factor explaining our evacuation numbers.

Hurricane Harvey’s size, intensity, and arcing track along the Texas coast (and then catastrophic stalling) was a worst-case scenario for coastal and inland flooding, brought home by media and social media coverage, particularly in and around Houston. In Florida we were seeing Harvey’s effects in Texas while also nervously watching Irma’s category and size increases in the Caribbean — with a projected track cone that for days encompassed the entire state.

Indeed, until the models started shifting its core to the west, but not sparing the Keys, Irma’s eyewall was heading straight into southeast Florida and then likely northward along the densely populated east coast, a worst-case Florida scenario. It seems clear that Harvey’s impact in Texas was preying on the minds of South Floridians.

The fifth component explaining our evacuation from Irma was the clear, consistent, and truly relentless messaging through the media — from the governor on down to local emergency managers — to “evacuate.” While the intent was to evacuate from Zones A, B, and parts of C, it’s not clear how the public interpreted and acted on that. Was it interpreted as evacuate locally (for example to Zone D) or head way north, including out of state, on Florida’s limited number of major arteries? This is a fundamental research question that has major evacuation planning implications for all of us: those who stayed and those who left.

In future evacuation calls, the people who left this time may be reflecting on their Irma experiences (the stresses of travel, lodging, return, and recovery) when the next major hurricane is tracking toward us. They may think “I’ll never do that again.” On the flip side, those of us who hunkered down and rode out the storm itself but then also had to deal with the general disruption and the uncomfortable lack of electricity for days, might be considering a different version of “I’ll never do that again” — and leave. That is, emergency managers and planners from all levels of government, and such private sector areas as fuel suppliers and the hotel industry, need to know much more about the future intentions of those of us who evacuated (and from where, how, to where, and when) and those of us who stayed — because we all know that there will be a next time.

Richard S. Olson, Ph.D., is professor and director of the Extreme Events Institute and International Hurricane Research Center at Florida International University.