Koski Dam Reservoir Report
Nearby: Smith (Steve) Dam Gochenour Dam
Last Updated: December 13, 2025
Located in Harrison, Iowa, the Koski Dam is a private earth dam designed by the USDA NRCS with a primary purpose of flood risk reduction.
°F
°F
mph
Wind
%
Humidity
Summary
Completed in 2011, this dam stands at a height of 41 feet and stretches 500 feet in length, providing a storage capacity of 48 acre-feet and a surface area of 2 acres. Situated on a tributary to Willow Creek, the dam serves multiple purposes including fish and wildlife pond creation, grade stabilization, and recreation.
Despite its low hazard potential, the condition assessment of the Koski Dam has not been rated, and there is no information available on its emergency action plan or risk assessment. As a non-federally owned structure, the dam does not fall under the jurisdiction or regulation of any state agency. With no inspection or enforcement protocols in place, the maintenance and safety of the dam rely solely on the private owner. Despite these limitations, the Koski Dam remains a key asset in managing flood risks in the Missouri Valley area.
Water resource and climate enthusiasts can appreciate the ecological and recreational benefits provided by the Koski Dam, while also recognizing the importance of ongoing monitoring and maintenance to ensure its continued effectiveness in flood risk reduction. The collaboration between private owners and government agencies, such as the USDA NRCS, highlights the importance of partnerships in safeguarding water resources and enhancing community resilience to climate-related challenges. As discussions around climate change intensify, structures like the Koski Dam play a crucial role in mitigating the impacts of extreme weather events and protecting vulnerable communities.
Year Completed |
2011 |
Dam Length |
500 |
Dam Height |
41 |
River Or Stream |
Trib to Willow Creek |
Primary Dam Type |
Earth |
Surface Area |
2 |
Drainage Area |
0.28 |
Nid Storage |
48 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
41 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Soldier River At Pisgah
|
112cfs |
Boyer River At Logan
|
417cfs |
Little Sioux River Near Turin
|
1040cfs |
Monona-Harrison Ditch Near Turin
|
158cfs |
Maple River At Mapleton
|
323cfs |
Missouri River At Decatur
|
15500cfs |
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.
Koski Dam