HURRICANE EVACUATION ANALYSIS
CORPUS CHRISTI — Hurricane evacuation zones in the Coastal Bend have shrunk, but that doesn’t mean residents outside those zones should be any less vigilant.
The state previously based its maps of the area on projected storm surge and wind for hurricanes of various strength, with risk zones extending 30 miles inland for Category 5 storms. The map used by the city of Corpus Christi as a guide showed the entire city divided into evacuation zones.
New maps adopted by the state before last year’s hurricane season take wind out of the equation, relying only on models of storm surge, the deadliest of a hurricane’s destructive forces. Now the city’s zones extend only to Weber and Chapman Ranch roads for the strongest storms. Also, now the state maps refer to the zones as evacuation zones rather than risk zones.
The shift marks a change in thinking toward a “run from the water, hide from the wind” philosophy to which the National Hurricane Center and officials along much of the country’s coastline subscribe.
“You want to evacuate as few people as possible,” National Weather Service meteorologist John Metz said. “It’s disruptive to society, and it’s expensive. You want to minimize that as much as possible, but at the same time you don’t want to risk lives.”
As the local warning coordination meteorologist, Metz advises local emergency officials as storms approach. Hurricane season runs June through November, with August and September traditionally the worst months for Texas.
“Even though the wind may not be an integral part of study, that doesn’t mean emergency management is going to ignore it,” Metz said. “I think it’s inherently built into the decision-makers, the emergency managers, the mayors and judges, the folks who have to make the call to evacuate.”
The change was outlined in a 2008 federal study, which says the shift was needed in response to Hurricane Bret. Bret’s intensity increased suddenly as it approached the Coastal Bend in 1999, leaving the city of Corpus Christi with little time to evacuate. Officials did not have good information on which areas were in the most danger.
“Since surge is still the greatest potential threat to human life posed by a hurricane, decision-makers have to know where the surge will go, how many people reside in those areas, and how long it will take to move those citizens out,” the report says.
The study primarily provides local officials with estimates on how many people might evacuate and how long it would take to clear the city under different storm scenarios. Evacuation zone maps are the basis of those calculations.
Tom Millwee, the retired director of the Governor’s Division of Emergency Management, said he is concerned the maps send the wrong message to the area’s inland residents, who might not realize they need to prepare.
“My fear is that you’re going to have people who say, ‘Honey, we need to evacuate but we’re not even in a risk zone,” Millwee said. “Then all of a sudden you have panic. That’s why I’m surprised that they made this switch.”
The wind-and-surge philosophy had been used since 1983, when the initial hurricane study for this area was completed, according to the federal report. The study was conducted by a contractor for the U.S. Corps of Engineers and Federal Emergency Management Agency.
Danielle Hale, the Coastal Bend regional liaison for the division of emergency management, said the old maps, which showed risk areas 30 miles inland, were based on the area of the state with the most risk from storm surge, Southeast Texas. The 30-mile line was extended along the coast for the sake of conformity and was used to keep people safe from surge and wind.
When the federal government undertook a study several years ago to re-do the Coastal Bend maps, local emergency management officials asked for the maps to be redrawn, Hale said.
“Storm surge does not go anywhere near (the 30-mile line),” she said. “The local emergency management coordinators were the ones who said we want something that adequately represents our threat areas and not some arbitrary line that was drawn that no one can defend with science.”
The city of Houston’s deadly evacuation in advance of Hurricane Rita in 2005 also had local emergency coordinators worried that evacuating too large an area could be risky.
But the state rejected the first draft of the federal study in 2005 because it excluded wind altogether. The contractor then added some calculations of evacuation times that included people outside the surge zones who might evacuate because of wind, such as those who live in mobile homes.
The maps were not the main point of the study and aren’t to be used as the sole tool for evaluating evacuations, Hale said.
“It did get some folks concerned because this is what the city and some of the counties the Coastal Bend are going by for their educational materials,” she said.
The state has the new maps posted on its emergency management Web site, and the city has a similar map, though some zones are slightly different. The city began using a map from the state in 2007, before the study was finalized.
Randy Sijansky, the city’s emergency management coordinator, said the city uses the zones to estimate which residents are in the most danger but takes wind into account when making decisions.
“We want to give the public all the information possible to make that decision and be transparent about it,” Sijansky said.
All local officials interviewed emphasized personal responsibility, no matter in which part of the area one resides.
Well ahead of a storm, residents need to determine whether they should leave for medical reasons, because their house is in a low-lying area vulnerable to floods, because they live in a mobile home or poorly constructed home, or if there is a possibility of being stuck in a South Texas summer without power or air conditioning.
“The fact of the matter is, no map can give you that level of definitive decision making,” Corpus Christi Assistant Fire Chief Michael Hernandez said. “To make a decision that you’re going to stay because you’re outside the red line on the map is not a good thing to do.”
And regardless of lines on a map, county judges still can call for evacuations of their entire counties. Nueces County Judge Loyd Neal said he worries about flooding from rain in low-lying areas of the county in Robstown and in colonias, which have poor drainage.
“We’re not a shelter county — we’re an evacuation county,” Neal said. “I would not (call for evacuation) without consulting with the mayors. But at the end of the day, it is not an argument. I have to make that call.”
The federal study does caution that wind is still a concern and officials may decide to extend the evacuation area farther inland and need to account for longer clearance times.
It could take up to 45 hours to clear out Nueces and San Patricio counties in the event of a large storm during tourist season, according to the study. That time decreases to 27 hours with full contra-flow of Interstate 37 — meaning all lanes become northbound — with individual cars being stuck in traffic for about 22 hours.