New wave
It’s been nearly two decades since the city last revised its extensive mapping ofHonolulu’s tsunami evacuation zones. In a federally funded six-year project using new computer mapping technologies to reassess Oahu’s coastal communities, emergency management officials are making some significant changes.
“Looking at downtown, they have some large changes,” said John Cummings, spokesman for the Honolulu Department of Emergency Management. “We’re anticipating a lot more inundation in the Waikiki area than previously. We had to add maps for Pearl Harbor and Kaneohe.”
Waikiki is unique in that it’s the only county that practices vertical evacuation.
Cummings says it’s also critical for people in that densely packed neighborhood to be prepared.
“We’re talking 200,000 people in a two-mile section,” Cummings says. “If you have a building in the evacuation zone that’s six or more stories of steel and reinforced concrete, you evacuate by going up.”
The map updates were made using all the data used for the most recent 1991 revision–a century of historical and archival tsunami records–but with added computer technology based on topographical information. While old records show the location of the high-water mark from a tsunami, new assessments aim to better understand how the landscape will affect the way a wave behaves in any given region.
“They actually had to develop new computer modeling to show what tsunami wave energy would do when it came into nearshore areas and when it came onto land,” Cummings says.
“If a tsunami hits a flat open beach, it acts differently than if it hits a rocky beach or a road. They used a lot of LIDAR [light detection and ranging] data. It’s kind of like an airborne sonar system to map those areas. They referred to this as 3D mapping. It gave you a visual picture of the nearshore and onshore areas, which they could model for a tsunami scenario.”
City officials are also working to develop comprehensive evacuation plans with schools, like many charter schools, that weren’t open in 1991. Shelter locations haven’t changed, as shelters are never officially desgnated or opened until “post-event,” in a tsunami.
While the mapping changes, Cummings says the public’s responsibility remains the same.
“We’re talking about changes but something that didn’t change is our basic message,” Cummings says. “If you are in an evacuation zone, get out of the zone. And if you’re not, stay where you are, get off the road.”
He says he knows there are still people who ignore tsunami warnings under the assumption that it’s unlikely a catastrophic wave might actually hit.
“People need to understand where they are in relationship to these zones,” Cummings says. “Current science and technology says those areas will be impacted. History shows. You’re talking history, you’re talking technology, are you going to gamble or not? For me, I would clear out.”
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