A University of Hawaii geologist says people should not be living at the base of slopes because of potential rockfalls.

"We all have to realize it’s a natural process. If you’re going to live there, you’re going to have to deal with that natural process," said Floyd McCoy, a geology professor at Windward Community College who is affiliated with the graduate faculty at the Department of Geology & Geophysics at the University of Hawaii at Manoa.

"There’s nothing we can do about it," he said. "We should not be living at the base of such slopes, period."

In a five-day period, boulders in two neighborhoods on Oahu rolled down hillsides and hit homes. Yesterday, an Aina Haina resident reported that a 5-foot boulder struck the left corner of his hollow-tile garage at 458 Hao St. No one was hurt.

On Saturday, a large boulder in Aiea Heights struck a two-story home, injuring two people. The boulder fell two days after a heavy rainstorm. The hillside at the Aiea Park Place subdivision is privately owned.

Aina Haina resident Noah Fiddler told the Honolulu Fire Department he believes the boulder fell Wednesday night, but he was not home at the time. Firefighters arrived yesterday morning to assess the situation.

"Luckily it didn’t come near the house," said Fiddler. His garage is about 15 feet from his three-bedroom home.

Fiddler, who has lived there for 23 years, said it was the first time a boulder had fallen on his property. The hillside is privately owned.

"You’ve got to be kidding me," neighbor Debra Witteveen said after she walked up Fiddler’s steep driveway to see the boulder lodged against his garage. "Now that gives me chicken skin. One of these days, something bad is going to happen. Instead of a garage, it will be a person."

An Aina Haina resident since 1997, Witteveen said she is aware of the potential for a rockfall but tries not to dwell on it.

"It scares me," she said.

On the same street in 2007, a 4-foot boulder crashed into the rear of a home during a rainstorm. The boulder damaged a window, a hollow-tile wall and part of the roof.

Residents assume the risk of rockfalls when they purchase homes next to hillsides, said McCoy.

Stabilization measures that include metal netting and chain-link fencing are installed at Makapuu and other parts of Oahu to reduce the risk, but McCoy said any such steps are temporary.

"Geology will ultimately win," he said.

"The problem is education. We just have to educate the public about the natural hazards and live with them, not so much mitigate them, but live with them," he added.

Paul Wessel, a geophysics professor of the University of Hawaii, said, "All you can do is survey the land above you to look for precarious rocks that don’t look very stable and try to prop them up better." But often determining land ownership becomes problematic, he said, delaying survey and mitigation work.