The question has been before big-city leaders several times in recent years, and it was the question Houston faced as Hurricane Harvey barreled toward the fourth largest city in America.
Mayor Sylvester Turner decided not to order an evacuation, a decision that's come under scrutiny since the storm landed, flooding large swaths of the city and leaving thousands of people stranded on top of their water-filled homes. Texas Gov. Greg Abbott, on the other hand, urged people the day the storm made landfall in the Houston area to leave, adding to the political fallout from Turner’s decision.
But even as rain continues to fall and levees break, prompting evacuations, the mayor defends his decision.
"You cannot evacuate 6.5 million people within two days. You cannot. That would be chaotic ... you would be putting people more in harm’s way," Turner said in a news conference on Tuesday.
Houston's history has taught them as much.
In 2005, Hurricane Rita struck Houston just weeks after Hurricane Katrina pummeled New Orleans and left 1,833 people dead. The mayor of Houston at the time, Bill White, called for an evacuation of the city. Highways were choked with traffic, fights between motorists broke out, people died from hyperthermia in the intense heat and 23 nursing home patients were killed as a bus evacuating them caught fire and exploded near Dallas.
Turner vowed not to repeat that mistake. In his position, other city officials likely would have come to the same conclusion.
Pete Gomez has spent more than 30 years with the City of Miami's Department of Fire Rescue and he currently serves as both the department assistant fire chief and assistant chief of emergency management for the city. While his city did evacuate 25 years ago when Hurricane Andrew barreled through South Florida, he supports Turner's decision to not order an evacuation and advise Houston residents to shelter in place.
"Think about putting 6 million people on the road and possibly into the eye of the storm during the event," Gomez says.
FEMA director William "Brock" Long echoed the same sentiment, saying on Sunday that it would take days to evacuate a city as large as Houston.
Mayors of any large metropolitan area are presented with a complex set of problems when a storm bears down on their cities: Elderly, poor and homeless residents may be unable to evacuate, predictions of where the storm will land are subject to sudden change, and the roads and transit systems may be unable to handle the millions of people on them.
When Hurricane Andrew hit South Florida in 1992, cities ordered massive evacuations and had to hope that residents wouldn't be caught on the road in the storm.
The evacuation was largely a success and likely reduced the number of lives lost to the storm, according to a report released by the National Hurricane Center. But the forecast that officials used to make evacuation decisions was wrong -- the storm hit south of where it was projected to make landfall. Luckily, the evacuation got most of those living in the storm's path out of the way in time, Gomez says.
Two decades later, New York City braced for Hurricane Sandy -- a storm not as strong as Andrew, Rita or Harvey but unlike any it had seen in modern history. In preparation, the city evacuated some sections. In a worse-case scenario, where New York City evacuates all six of its zones deemed at risk of coastal flooding, emergency personnel officials are confident they can move all 3 million of those residents out of harm’s way in 48 hours.
But New York's geography and infrastructure make evacuations less of a heavy lift than for cities like Houston.
"One of the things pre-storm that is a benefit is our subway and bus system," which takes excess car traffic off the roads, says Megan Pribram, New York City's assistant commissioner for planning and preparedness.
Houston covers an area more than twice the size of New York City but lacks its mass transit system. Two days may be enough to move 3 million people several miles with the help of subways and buses, but in sprawling Houston, evacuating the city in search of higher ground means traveling further, almost exclusively by car, and battling massive amounts of traffic, says Gomez.
Even if Houston had ordered mass evacuations, it’s not a certainty that people would have left. Gomez was deployed to the Gulf after Katrina. He interviewed scores of people who rode out the storm.
“Many times when you do issue an evacuation order, it’s impossible to enforce," says Gomez. "They say ‘I survived previous hurricanes and didn’t think this was going to be worse.""
*Correction: A previous version of this article stated an incorrect year for Hurricanes Rita and Katrina. They occurred in 2005.
