Flood risk rising in Hilo

By Hugh Clark
Advertiser Big Island Bureau

HILO, Hawai'i — The risk of flooding in Hilo has been reassessed in the wake of a November storm that caused at least $70 million in losses, and experts are now calling it a dangerous and expensive problem.

Palai and Waiakea streams near Hilo may pose greater dangers than previously believed and could require bridge replacements costing up to $30 million, federal officials warned yesterday at a flood symposium conducted by the Center for the Study of Active Volcanoes at University of Hawai'i-Hilo.

The bad news is that federal disaster money will not be available if either bridge has to be rebuilt to handle storm conditions, the county Department of Public Works reported. Because the bridges are not damaged, they are not eligible for these funds.

Federal Emergency Management Agency mitigation specialist David Kennard said the current assessment of flood zones in Hilo may be inadequate. "There was considerable flooding outside the special flood hazard zones," he warned.

The upper area of Hilo from Kaumana to Waiakea Uka may need review by the U.S. Corps of Engineers, and new maps may be required to establish the flooding risks, said Kennard.

The "re-study" could alter future residential developments above Hilo, Kennard said.

"This could be a double-edge sword," said Bill Davis, a Hawai'i County Civil Defense administrator who attended the symposium, because broader flood-hazard zones could increase insurance costs and reduce property values in the area.

The storm, which hit the Big Island Nov. 1-2, established all sorts of records, said Thomas Heffner, a warning-coordination meteorologist for the National Weather Service. He described it as "a hybrid storm" combining a local weather phenomenon with the remnants of Tropical Storm Paul that was generated from the South Pacific.

The storm produced rains that poured 39 inches onto Kapapala Ranch, with an average of four inches an hour falling for a six-hour spell. It dropped more than two feet of rain on much of Hilo and upper Puna.

This resulted in "exceptional runoff with monstrous lateral force," Heffner said, causing the loss of four bridges in Ka'u and tearing out a key culvert on Komohana Street in Hilo that cost $4.8 million to replace.

The culvert reopened in February.