Research helping redraw Hawaii’s tsunamis threat maps
By Eloise Aguiar
Advertiser Staff Writer
Hundreds of homes and businesses in areas long believed to be safe from a tsunami could be added to O'ahu's evacuation map in light of new research.
Even as up to 50,000 people statewide evacuated during the Feb. 27 tsunami warning, work was already well under way to upgrade Hawai'i evacuation maps, which are nearly two decades old.
The good news is that the maps created in 1991 are still largely accurate, and inundation zones will mostly remain the same.
However, an examination of the five most dangerous tsunamis that struck the Islands in the last 100 years has found that the threat in some areas may be greater than originally believed.
The result could be expanded evacuation zones in areas including Waialua and Hale'iwa, around Kāne'ohe Bay and along O'ahu's South Shore. Other areas could see evacuation zones shrink.
"I hate broad-brush generalities, but in general I think on the south coast of O'ahu, we're going to need to evacuate more people," said Peter Hirai, deputy director for the city Department of Emergency Management.
Currently, no evacuation is called for around Kāne'ohe Bay.
"We always said if you live around Kāne'ohe Bay, so long as you're more than four feet away from the edge of the water, you're OK," Hirai said. "That's changed."
The new tsunami research, conducted by Kwok Fai Cheung, a University of Hawai'i professor, makes recommendations, but it's up to counties to decide whether to expand or shrink evacuation zones.
O'ahu has already received its updated inundation zones and is considering map changes this month with plans to present them to the community for input once the maps are completed.
Hirai and other officials declined to release specifics about the areas affected because they are still in the process of deciding what changes, if any, to make.
LEARNING FROM 2004
The project was prompted by the Sumatra-Andaman earthquake of December 2004, which produced a killer tsunami in the Indian Ocean that swept across a dozen countries and killed hundreds of thousands.
The state Legislature in 2005 alloted $2 million a year for two years to state Civil Defense to improve its emergency shelter program, modernize its siren warning system and update the inundation zones, said Ed Teixeira, vice director of state Civil Defense.
The National Tsunami Hazard Mitigation Program has kicked in about $300,000 so far and is expected to continue funding the project with about $200,000 a year.
FEMA and the Army Corps of Engineers provided topographical information with a LiDAR (Light Detection And Ranging) survey at a cost of about $700,000 to the state, Teixeira said.
Yoshiki Yamazaki, one of Cheung's graduate students, developed the NEOWAVE model for the project, for which he won an award.
The end product is a computer model that uses the LiDAR survey and data collected after the major tsunamis of 1946, 1952, 1957, 1960 and 1964 to create the new inundation zones. The data includes runup, or how high above sea level a wave gets, and inundation, or how far inland it travels.
Cheung was required to take the Sumatra-Andaman quake of 2004, double it and place it at sites around the Pacific, then run the model to see what it would do to Hawai'i, Teixeira said.
"Our tsunami maps now from the 1991 era still hold up with some exceptions," he said, adding that the Hilo zone may change. "Where Hilo has a very generous evacuation zone (Cheung) is recommending not going so far."
REVISING THE MAPS
Other areas the city will have to look at are Hale'iwa, Waialua and the area around the Dillingham airfield, which traps water, Teixeira said. Honolulu Harbor near Iwilei, and the area mauka of Kalaniana'ole Highway may need some attention as well, he said.
The original maps of 1991 were prompted by an all-out evacuation in 1986 that caused gridlock on shorelines when the wave struck. Fortunately, it was a small tsunami that caused no damage.
"That was a big screw up by the state and the county," said George Curtis, who created the 1991 maps and is the tsunami adviser for the Big Island. "They sent everybody home and it had nothing to do with whether you were near the shore or not. They closed Ala Moana shopping center, and it's perfectly safe."
Recognizing that good maps would reduce the problem, Curtis lobbied the Legislature for money and developed the maximum expectable inundation from probable tsunami directions, he said. Those maps were designed by county civil defense agencies, he said.
With as little as three hours to evacuate threatened areas, the agencies must decide who will evacuate, keeping in mind the 1986 gridlock, Curtis said.
While Curtis, who is a consultant for the new project, was pleased that the maps created by his old one-dimensional model are still valid, he said this new model is more accurate.
"It's much better modeling and the thing that's much improved about it is their topographic data," Curtis said. "It's a 2-D model, compared to a one dimensional so it's a far better model and that's something to emphasize."