Rockfalls are persistent and expensive dilemma
Hawaii hillsides are constantly in a state of instability
» Mitigation work progresses at slide sites
» Rockfalls part of erosion
As the state continues work after Saturday's rockfall at Waimea Bay, officials are looking at other rockslide hazard sites and what needs to be done.
Some four years since officials first listed the top 10 hazard locations, the work has been slow in coming, and officials are finding that fixing the problems will cost a lot of money.
Near Waimea Bay as of yesterday, workers took away 70 truckloads of rocks and debris from the rockfall, which partially blocked Kamehameha Highway.
Experts say Hawaii's warm temperatures, fractured rocks, lush vegetation, rainfall and sometimes earthquakes combine to make rockfalls inevitable.
STEADYING OF SLIDE SITES
The state has done work to some sites of the following top 10 rockslide hazard sites on Oahu:
1. Kalanianaole Highway at Makapuu *
2. Kamehameha Highway near Waimea Bay
3. Kamehameha Highway near Kahuku
4. Kalanianaole Highway between Le Jardin Academy
5. Kalanianaole Highway near Castle Junction **
6. Kamehameha Highway near Kipapa Bridge *
7. Kamehameha Highway near Wahiawa
8. Kailua Road before Kailua Town *
9. Farrington Highway before Yokohama Bay
10. Kamehameha Highway near Wahiawa
* Some work done to the site
** Work completed at the site
No work done to sites without an asterisk (*)
Hawaii hillsides constantly in a state of instability
Keeping trails and roads safe is a never-ending task
Isle experts say rockfalls are part of nature's course.
The combination of Hawaii's warm temperatures, fractured rocks, lush vegetation, rainfall and, at times, earthquakes, contribute to the destabilization of rocks and slopes, experts say.
"The warm, sunny and moist conditions that help break down the slopes also help the plants grow, and the plants help break down the rocks," said Steve Martel, professor of geology and geophysics at the University of Hawaii.
Man-made processes such as road construction also play a role to the weakening of slopes, Martel said. "Putting in roads typically steepens the slopes and can contribute to the destabilization of the slope," he said.
A rockfall Saturday closed Kamehameha Highway at Waimea Bay over the weekend. That portion is an example of how the slope was cut to construct the roadway, Martel said.
Brennon Morioka, deputy director of the state Department of Transportation, said, "We try to be proactive and develop these rockfall hazard locations where were can try to anticipate these type of events and provide some kind of mitigated effort to prevent them from happening."
"But we have hundreds and hundreds of miles of road, and these kinds of things can occur out of nowhere," he added.
"Sometimes it occurs where we never expected it. We never expected the mudslide at Pali Tunnels, but it came down," Morioka said. "So these things are very unpredictable."
Martel stressed that Hawaii needs a geological survey to get a comprehensive look at addressing slope stabilization in the islands. "Hawaii is the only state with no state geological survey, and that puts us at a disadvantage with regard to addressing the varied geological hazards that exist here," he said.
Currently, the state Department of Land and Natural Resources is taking steps to identify hazardous sites along state trails to determine where signs are needed to warn people of potential rockfalls, said Peter Young, the department's director.
The action was a result of the state being held responsible for eight people who died and many others who suffered injuries at Sacred Falls in May 1999. It was ruled that the state failed to adequately warn visitors of the rockfall hazards, primarily in the waterfall area.
Young also said more awareness is needed of the hazards as the population grows in the state and residential developments are constructed near slopes.
"It doesn't mean stop everything. It just means that we need to be far more proactive and not put people and property at risk, because the Waimea rockfall reminds us that rocks will fall," Young said.
Rock hazards spur constant repairs, costly plans
The work on top rock hazard areas published four years ago trudges along, and state officials are finding that fixing the problems will be costly.
The state plans to do slope improvement work to the lower part of the cliff side at Makapuu along Kalanianaole Highway. The project is in the design process. Officials hope to start work later this year, said Scott Ishikawa, Department of Transportation spokesman. About $11 million was set aside in the budget for the project.
The upper part of Makapuu was completed in 2003. Metal netting was installed, Ishikawa said. The state also cut back the hillside at Castle Junction.
State transportation officials are looking into realigning Kamehameha Highway to the cliff side on the Haleiwa side near Waimea Bay.
At the cliff side along Kamehameha Highway near Kipapa Bridge, officials are discussing the possibility of cutting the hillside and widening the two-lane bridge to create a four-lane bridge, Ishikawa said. The project is expected to cost tens of millions of dollars.
Along Kailua Road just before Kailua Town, contractors are working on the hillside that was a source of multiple landslides that occurred in March 2006. Work is expected to be completed by August, Ishikawa said.