The site of a Monday rockslide that injured a woman near the Diamond Head lighthouse shows signs of other recent slides, according to the head of the Coast Guard's civil engineering unit in Honolulu.

Cmdr. Roger Wykle, commanding officer of the Coast Guard's Honolulu civil engineering unit, surveyed the site for about an hour yesterday with another engineer and found evidence of other recent rockslides.

Monday's Memorial Day slide, Wykle said, was, "in my opinion, just natural slope erosion that occurs in Hawai'i."

The Coast Guard will recommend leaving the debris where it landed in a pile about 8 feet high and 50 feet wide, said Coast Guard Chief Petty Officer Marsha Delaney.

"There were big, large chunks of rocks," Wykle said. "Some of it fell on Coast Guard property and part of it fell on the state, all at the same time."

At about 8:30 a.m., a 44-year-old woman was picnicking at the base of the lighthouse's cliff with three other adults and two children when she was hit by the falling debris.

The woman suffered head and back injuries and was taken to The Queen's Medical Center in serious condition, fire and emergency services officials said.

Honolulu police told Jessica Lani Rich, president and executive director of The Visitor Aloha Society of Hawai'i, that the victim lives in Hawai'i and is not a tourist, Rich said.

"Our thoughts are with the woman who was injured and her family," Delaney said. "We know they're getting the support they need from the hospital and their family and friends."

Yesterday, the area was cordoned off by yellow tape. But beachgoers continued to walk over the area and ignored rock-slide warning signs, Wykle said.

Much of yesterday's efforts by city officials, the Coast Guard and state Department of Land and Natural Resources focused on determining which of the agencies owns the land where the rockslide originated.

A brass plate or brass pin designed to mark the dividing line between state and federal land on the hillside was gone yesterday, Wykle said. Maps show that the pin or plate was installed close to where the slide began, he said.

The brass marker "was set in concrete right on our property corner," Wykle said. "It looks like it may have eroded over the years. We estimate it was right above where the rockfall occurred."

More sophisticated surveying equipment will be needed to determine the exact property lines, Wykle said.

But Deborah Ward, DLNR spokesman, yesterday said state officials believe the rockslide started on Coast Guard property.

"According to our site inspection and a review of land documents, we believe it is Coast Guard property and adjacent to that is city and county property on the Kahala side," Ward said. "That (brass) pin would have helped. Still, there are other maps that can be referred to."

Wykle said some agency other than the Coast Guard installed rockslide warning signs on either signs of the lighthouse parking lot and the Coast Guard may recommend installing more signs.

Ward said that there is only one warning sign near the city's beach park.

"We're only aware of one sign at the end of the beach road," Ward said. "We're not sure who owns the sign."

City officials also were at the scene yesterday reviewing maps and taking photos, said city spokesman Bill Brennan.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.