Tomahawk Detention Dam Reservoir Report
Nearby: Jordan Dam Judy Detention Dam
Last Updated: December 19, 2025
Tomahawk Detention Dam, located in Valley, Montana, serves as a critical infrastructure managed by the Bureau of Land Management to reduce flood risks along the Willow Creek and Milk River.
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Summary
Constructed in 1962, this gravity dam stands at a structural height of 23 feet and a hydraulic height of 18 feet, with a capacity to store up to 556.3 acre-feet of water. Despite its low hazard potential, recent assessments have deemed its condition unsatisfactory, prompting the need for further inspection and potential risk management measures.
The dam's primary purpose of flood risk reduction highlights its significance in protecting surrounding areas from potential water-related disasters. With a surface area of 95.71 acres and a drainage area of 0.7 square miles, Tomahawk Detention Dam plays a crucial role in safeguarding the local community and infrastructure from the impacts of extreme weather events. While its current risk assessment indicates a moderate level of concern, ongoing efforts by the Bureau of Land Management are essential in ensuring the continued safety and effectiveness of this vital water resource structure.
As enthusiasts in water resources and climate, understanding the intricacies of Tomahawk Detention Dam provides valuable insight into the management and maintenance of essential infrastructure. By staying informed and engaged with the latest data and assessments, individuals can contribute to the preservation and improvement of water resource systems like Tomahawk Detention Dam, ultimately enhancing resilience against the challenges posed by climate change and water-related hazards.
Year Completed |
1962 |
Dam Length |
1738 |
River Or Stream |
WILLOW CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
95.71 |
Hydraulic Height |
18 |
Drainage Area |
0.7 |
Nid Storage |
556.3 |
Structural Height |
23 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Tomahawk Detention Dam