The rules…and the do’s and don’ts » Yale Climate Connections



A few years ago, a large, slow-moving hurricane threatened a place I knew well. Close family members were not only in the path of the storm, but lived in an area under mandatory evacuation. While many of their neighbors shut down and hit the road, they, like others, saw only a road full of complications from unnecessary panic. When decisions seem paralyzing, it’s human to delay.

Their adult children weren’t leaving, and they certainly weren’t about to leave their children — even though their children were healthy in their twenties and even for a hurricane. “It’s only a Category 1. They say it’s not going to be so bad.” The elusive “they”. It taunts every meteorologist who has ever made a forecast, but with no face or name to reject. I stood in front of the concrete walls of my office at the National Hurricane Center in Miami that day in 2012 looking for something between empathy and outrage. “I’m the ‘they’, and I tell you it’s going to be bad!” I erred on the side of indignation.

What motivates us to evacuate?

Evacuations are a complicated business. Compliance with evacuation orders is not great – between 30% and 70% people under mandatory evacuation orders in the United States typically depart, with higher compliance for stronger hurricanes. To complicate matters, we add voluntary evacuations for good measure. Ordering a voluntary evacuation is paradoxical at best and counterproductive at worst. How is an order voluntary? Do voluntary evacuations imply a less credible threat? Studies show that voluntary evacuation calls concern as effective as not having an evacuation order at all.

Evacuation orders are just one line in the Rubik’s cube. We cannot discuss evacuations without first acknowledging that those most disproportionately affected by hurricanes – the elderly, the economically disadvantaged, communities of color, people with disabilities, etc. – are often the ones left behind. Coordinating comprehensive plans to help people and households with physical or financial limitations evacuate is an essential first step.

But what about those who can leave and choose to stay? Social scientists have identified a cacophony of possible barriers, from pets and hotel fees to social cues and community ties, that impede personal evacuation decisions. From decades of evacuation researchhowever, three factors in particular convince people to leave: the issuance of mandatory evacuation orders, a perceived threat of flooding, and early official notices to leave.

All disasters are local

There is an adage in emergency management that disaster response is locally executed, state managed, and federally supported. This means that local leaders are the ones who drive decisions affecting their threatened communities. This is especially true for evacuations. With few exceptions, such as in South Carolina where the governor directs evacuations, the federal and state governments are largely indifferent to evacuation orders. While federal and state agencies support evacuation and sheltering operations, typically municipal, county, parish, or regional governments define their evacuation zones and decide if and when to evacuate an area. It should be like this. Washington cannot know whether the community surrounded by low-walled earth levees at the head of the Five-Forks River should repack it.

Evacuation rules

Hurricane evacuations are a bespoke service, but some universal rules apply. Although some high-risk populations like those living in nursing homes or manufactured homes may need to evacuate in high winds, the vast majority of hurricane evacuations are based on life-threatening surge flooding. of storm. Storm surge atlases developed by the National Hurricane Center outside of hurricane season allow officials to update and refine their evacuation zones before the first storm forms.

As the threat of storm surge helps officials decide if to evacuate, the timing of tropical storm winds (winds above 38 mph) helps decision makers determine when clear out. Thorough studies of regional and local population and behavior, nearby shelter capacity, and road networks help determine appropriate clearance times, the time needed to move at-risk populations to safety. The local authorities’ goal is to begin evacuations with enough time to get all evacuees to a safe location before dangerous tropical storm winds arrive. In some cases, these evacuations may only take a few hours, but in other high-density, storm surge-prone areas clearance times can be days.

The politics in play

The decision to evacuate an area is partly scientific, partly artistic and inevitably political. Officials who call for evacuation are usually elected or appointed, and a decision to go or not to go can have significant consequences for their municipality and their electorate, not to mention their own future.

Evacuations indirectly contribute significantly to hurricane deaths (about 15% of all indirect deaths caused by hurricanes are related to evacuation), so putting people on the road unnecessarily can be costly and deadly. In 2005, as Category 5 Hurricane Rita tracked down the Texas coast, nearly 4 million people blocked roads, many unnecessarily in a post-Katrina panic as “shadow evacuees (people who evacuate even if they are not directly ordered to do so). The result was 100 dead from evacuations alone, accounting for over 80% of storm-related fatalities. Officials may also worry about blase voters not to evacuate next time when a hurricane threat becomes a false alarm (many studies proved that the “crying wolf” concern was unfounded).

But delaying evacuations also has consequences. Those who are ordered to evacuate are much more likely to do so when given at least two to four days notice. Short-term evacuation notices are not always avoidable – especially with rapidly forming storms – but evacuation compliance is significantly lower when a day’s notice or less is given. When people stay behind who shouldn’t, it not only puts their lives at risk, but also those of the first responders and rescue teams that follow.

Managers are not always uniform or consistent in finding information on which to base their decisions. Civil servants and emergency managers may not have the appropriate technical training or skills to interpret complicated scientific products forecasters. Even common visuals like the much-maligned forecast cone can be a point of confusion for decision makers. They often have to make binary decisions based on unknown probabilities. Typical weather rules of thumb tend to break down when the weather turns extreme. A 40% chance of rain and a 40% chance of hurricane-force winds should cause very different behavior, but as scientists have found, that’s often not the case.

next time we will go

The personal call I made between forecasts for that late summer afternoon at the National Hurricane Center didn’t work. My family members stayed despite the mandatory evacuations. They were terrified, helpless against the dark whims and piercing hisses of the approaching storm. Their neighbors just a few miles away were flooded, but they didn’t.

They said they would evacuate next time, but science suggests otherwise. We tend not to change our future behavior based on near misses. It is only once we perceive that a threat is serious enough – whether or not – do we seek safety, but as we learned in Ian, with hurricanes and evacuations, for too many people, that next time may never come.

Michael Lowry is a hurricane specialist and storm surge expert with WPLG, the ABC affiliate in Miami, Florida. He is a former FEMA emergency management officer and senior scientist at the National Hurricane Center.

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