GEOLOGIC HAZARD ZONATION AT SACRED FALLS STATE PARK, OAHU, HAWAII, AND THE LEGEND OF KAMAPUA'A

On Sunday May 9, 1999 (Mother's Day) about 100 people were gathered at the base of Sacred Falls, an 80 foot waterfall in Sacred Falls State Park. At approximately 2:30 p.m. a loud roar was followed by a shower of rocks and woody debris. In seconds seven people lay dead (an 8th died later) and 50 more were injured, some with traumatic amputations and/or open brain-case injuries. Following the rescue operation the Park was closed on the recommendation of the State Geologist. The park remains closed, and unlikely to reopen.

The May 9th rock fall was small (25-30 yds3 ), consisting of weathered basalt and woody debris that originated 500 feet above the canyon floor in the basalts that form the nearly vertical canyon walls. During the last 150 feet of fall the rocks and debris were airborne, falling straight down into the impact zone at velocities of about 70-100 miles per hour. There was no place to hide in the narrow canyon adjacent to the plunge pool. A lawsuit was filed by survivors of the rock fall and relatives of the injured and dead against the state of Hawaii. Following a bench trial in which the judge found for the plaintiffs the suit was settled for approximately 8.5 million dollars.

Although the rock fall hazard in the canyon was obviously very high, the State of Hawaii had never conducted a geologic study of the rock fall hazard either prior to or after opening the Park; and did not adequately respond to numerous other indications of the high rock fall hazard nor adequately warn visitors.

Conversely, the high rock fall hazard in Sacred Falls Canyon had been recognized by the ancient Hawaiian's for hundreds, if not more than a thousand years. Portions of the legend of Kamapua'a (the Pig God) are readily interpreted as series of rock falls in Sacred Falls canyon, which killed people, thereby leading to restrictions on the usage of the area and conditions of usage. In a similar fashion, legends in other areas of Hawaii are based on what appear to be geologic processes. The geologic sciences are relatively young (slightly over 200 years in age) and the concept of "geologic hazard zonation" was developed in only the past 40-50 years. However, it appears that the native Hawaiians recognized and developed a form of geologic hazard zonation over a thousand years ago.