Twelve Mile Creek Watershed Site M-1 Reservoir Report
Last Updated: December 12, 2025
Twelve Mile Creek Watershed Site M-1 is a key flood risk reduction structure located in Union County, Iowa.
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Summary
Completed in 1983, this earth dam stands at a height of 66 feet and has a storage capacity of 27,200 acre-feet. It serves multiple purposes including flood risk reduction, recreation, and water supply for the surrounding area. The dam is regulated by the Iowa Department of Natural Resources and undergoes regular inspections to ensure its safety and effectiveness.
With a drainage area of 23 square miles and a surface area of 633 acres, the Twelve Mile Creek Watershed Site M-1 plays a crucial role in managing water flow and reducing the risk of flooding in the region. The dam has a spillway width of 4 feet and is classified as having a high hazard potential. Despite this classification, the structure is assessed as being in satisfactory condition, with a moderate risk level of 3 out of 5. It is owned and operated by the local government, with support from the Natural Resources Conservation Service in design and construction.
Overall, Twelve Mile Creek Watershed Site M-1 is an essential component of the water resource management infrastructure in Union County, Iowa. Its strategic location along Twelve Mile Creek ensures the protection of downstream communities from potential flood events, while also providing recreational opportunities and water supply benefits. The dam's design and construction by Hoskins - Western - Sonderegger, Inc. reflect a commitment to sustainable water resource management practices, making it a valuable asset for both the local government and the surrounding ecosystem.
Year Completed |
1983 |
Dam Length |
2100 |
Dam Height |
66 |
River Or Stream |
TWELVE MILE CREEK |
Primary Dam Type |
Earth |
Surface Area |
633 |
Drainage Area |
23 |
Nid Storage |
27200 |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
66 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
East Fork 102 River At Bedford
|
1cfs |
Raccoon River At Van Meter
|
1640cfs |
Thompson River At Davis City
|
22cfs |
South Raccoon River At Redfield
|
268cfs |
Raccoon River Near West Des Moines
|
1300cfs |
North River Near Norwalk
|
48cfs |
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.
Twelve Mile Creek Watershed Site M-1