Kaiwi State Scenic Shoreline Rockfall Hazard and Mitigation Design

Hawaii Department of Land and Natural Resources (DLNR)

Oahu, Hawaii

Kawai State Scenic Shoreline

The natural world can exhibit great beauty, but does not always provide a safe place within which to view that beauty, which is why the Hawai’i Department of Land and Natural Resources (DLNR) contracted with Hart Crowser to evaluate rockfall hazards along the walking path of the Kaiwi State Scenic Shoreline. DLNR became aware of potential hazards to hikers during an unrelated path reconstruction project, however, funds were limited and the timeline to address the hazards short. Hart Crowser was called in and quickly developed an innovative adaptation of established methods to evaluate the risk to hikers. With this approach we were able to achieve all project goals: public protection, minimal visual impact, budget and schedule.

Methods to predict whether a single rock will endanger the public or rank the relative hazard of large highway cuts are well-established. The same cannot be said for rockfall hazards to casual hikers. Hart Crowser developed a risk-based program to identify hazardous rockfall areas along the path in order to focus mitigation efforts only where needed. We combined a numerical rockfall simulation model (CRSP) with a modified rockfall hazard ranking system (FHWA), within a risk-based rockfall assessment model (AGS) to achieve DLNR’s goals.

The natural environment is not always a hospitable place and protecting the public from it can have an adverse effect on the very beauty that draws us there. Hart Crowser assessed not just the hazard of rockfall, but the risk to the public if the rockfall were to occur. This allowed us to identify which locations needed attention, rather than construct broadly protective, but unattractive, mitigation fences or netting. From initial assessment to construction, the project was completed rapidly to take advantage of already planned path closures. All of these things combined ensured that Hart Crowser’s approach made the best use of limited public funds while ensuring the public’s safety and protecting the natural beauty of the place.