Waubonsie Cr. Watershed Site M-1 Reservoir Report

Last Updated: December 13, 2025

Located in Mills County, Iowa, the Waubonsie Creek Watershed Site M-1 is a significant earth dam structure designed by the USDA NRCS in 1978.


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Summary

This local government-owned site spans 710 feet in length and stands at a height of 42 feet, providing flood risk reduction and recreational opportunities for the surrounding area. With a drainage area of 19.69 square miles and a storage capacity of 968 acre-feet, the dam plays a crucial role in managing water resources in the region.

Managed by the Iowa DNR, this dam on the Waubonsie Creek features an uncontrolled spillway with a width of 18 feet and is categorized as having a low hazard potential and satisfactory condition assessment. The site is regularly inspected every 5 years, with the last inspection conducted in July 2020. Despite its moderate risk assessment, the dam continues to meet regulatory guidelines and serves as a vital infrastructure for water management and environmental conservation efforts in the area. Water resource and climate enthusiasts are encouraged to visit this site to learn more about its role in safeguarding the local ecosystem.

Year Completed

1978

Dam Length

710

Dam Height

42

River Or Stream

TR-WAUBONSIE CREEK

Primary Dam Type

Earth

Surface Area

38

Drainage Area

19.69

Nid Storage

968

Hazard Potential

Low

Foundations

Soil

Nid Height

42
       
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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.