Johnston Dam Reservoir Report

Last Updated: December 12, 2025

Johnston Dam, located in Redfield, Iowa, along the Middle Raccoon River, was completed in 1971 by the USDA NRCS.


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Summary

This privately-owned earth dam stands at 43 feet high and spans 245 feet in length, serving primarily for fire protection, stock, and small fish pond purposes. With a storage capacity of 35 acre-feet and a surface area of 2 acres, the dam plays a crucial role in managing water resources in the area.

Managed by the Iowa DNR, Johnston Dam has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. Despite its moderate risk level, the dam has not been inspected since June 1978. Its spillway type is uncontrolled, with a spillway width of 0, and it has no outlet gates or associated structures. With a drainage area of only 0.1 square miles, the dam's impact on the surrounding environment is minimal.

Water resource and climate enthusiasts will appreciate Johnston Dam for its contribution to water management in the area. While its risk level is moderate, the dam continues to serve its primary purposes effectively. As a part of the larger water infrastructure in the region, Johnston Dam plays a vital role in supporting the local ecosystem and ensuring water availability for various uses.

Year Completed

1971

Dam Length

245

Dam Height

43

River Or Stream

TR-MIDDLE RACCOON RIVER

Primary Dam Type

Earth

Surface Area

2

Drainage Area

0.1

Nid Storage

35

Hazard Potential

Low

Foundations

Soil

Nid Height

43
       
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.