Natural Milk Dam Reservoir Report

Last Updated: December 21, 2025

Natural Milk Dam, located in Avoca, Iowa, is a privately owned earth dam that was completed in 2006 for the primary purpose of flood risk reduction along the TR- East Branch West Nishnabotna River.


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Summary

Designed by De Haan, Grabs & Associates, this dam stands at a height of 49 feet and has a length of 2640 feet, with a storage capacity of 378 acre-feet. Despite its low hazard potential, the dam is regulated, permitted, inspected, and enforced by the Iowa Department of Natural Resources.

The dam's location in Shelby County, Iowa, makes it a critical infrastructure for managing water resources and mitigating flood risks in the area. With a normal storage capacity of 276 acre-feet and a surface area of 7.8 acres, the Natural Milk Dam plays a vital role in controlling water flow and protecting downstream areas from potential flooding events. Its controlled spillway ensures safe discharge of excess water during heavy rainfall or high water levels.

As a part of the flood risk reduction strategy, the Natural Milk Dam has a very high risk assessment rating of 1, signaling the importance of its role in managing water resources and protecting the surrounding community from potential hazards. With its state-regulated status and adherence to inspection and enforcement protocols, this dam serves as a valuable asset in safeguarding the local environment and enhancing climate resilience in the region.

Year Completed

2006

Dam Length

2640

Dam Height

49

River Or Stream

TR- EAST BRANCH WEST NISHNABOTNA RIVER

Primary Dam Type

Earth

Surface Area

7.8

Drainage Area

0.05

Nid Storage

378

Hazard Potential

Low

Foundations

Soil

Nid Height

49
       
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.