Nuuanu Dam No. 4 Reservoir Report

Last Updated: December 19, 2025

Nuuanu Dam No.


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Summary

4, also known as Nuuanu Reservoir, is a vital structure located in Honolulu, Hawaii, along the Nuuanu Stream. Built in 1910, this earth dam stands at a height of 66 feet, with a hydraulic height of 69 feet and a structural height of 73 feet. It serves multiple purposes, including flood risk reduction, and has a storage capacity of 3,600 acre-feet. The dam is regulated by the DLNR and undergoes regular inspections to ensure its safety and functionality.

With a hazard potential rated as high and a condition assessment of fair, Nuuanu Dam No. 4 is considered to have a moderate risk level. The spillway of the dam is uncontrolled, with a width of 55 feet, and it has a maximum discharge capacity of 4,000 cubic feet per second. The dam covers a surface area of 25 acres and has a drainage area of 1.4 square miles. In case of emergencies, it is crucial for the authorities to have an effective Emergency Action Plan (EAP) in place to mitigate risks and protect the surrounding community.

Overall, Nuuanu Dam No. 4 plays a significant role in managing water resources and reducing flood risks in the region. As a local government-owned structure, it highlights the importance of proper regulation, inspection, and maintenance to ensure its continued effectiveness. For water resource and climate enthusiasts, this dam serves as a fascinating example of how engineering solutions can address environmental challenges and enhance community safety.

Year Completed

1910

Dam Length

2120

Dam Height

66

River Or Stream

NUUANU STREAM

Primary Dam Type

Earth

Surface Area

25

Hydraulic Height

69

Drainage Area

1.4

Nid Storage

3600

Structural Height

73

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

73
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.