Puukapu Watershed Retarding Dam R-1

About Puukapu Watershed Retarding Dam R-1

The primary purpose of Puukapu Watershed Retarding Dam R-1 is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Hawaii Dept Of Hawaiian Home Lands, Hawaii Dept Of Land & Natural Resources (state). It impounds the Lanimaumau Stream Offstream near Waimea Kuhio Village.

The dam stands 12 feet tall and stretches 4,340 feet across, creates a reservoir covering 185 acres, has a maximum storage capacity of 1,450 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1965, the structure is well into its service life at over 50 years old.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 05/31/2025.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Hawaii dam safety program can provide more specific information about emergency planning for this structure.

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