Nuuanu Reservoir No. 1 is an earth dam located in Honolulu County, Hawaii, built in 1905. It carries a High hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 34 ft34 ft tall and 588 ft long, taller than 78% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Nuuanu Reservoir No. 1
The primary purpose of Nuuanu Reservoir No. 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 Honolulu Board of Water Supply (local government).
The dam stands 34 feet tall and stretches 588 feet across, creates a reservoir covering 6 acres, has a maximum storage capacity of 63 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1905, the structure is over a century 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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 04/04/2024.
At 34 feet, this dam is taller than 78% of dams nationwide.
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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Hawaii |
| County | Honolulu |
| Coordinates | 21.33968, -157.83740 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 34 ft |
| Dam Height | 34 ft |
| Dam Length | 588 ft |
| Year Completed | 1905 (121 years old) |
Storage & Hydraulics
| NID Storage | 63 acre-ft |
| Max Storage | 63 acre-ft |
| Normal Storage | 44 acre-ft |
| Surface Area | 6 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 428 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Honolulu Board of Water Supply |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 04/04/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | HI00154 |
| Federal ID | HI00154 |
| More Info | State Dam Safety Program |