Derby Dam Reservoir Report

Last Updated: December 6, 2025

Derby Dam in Iowa, also known as the Soap Creek Reservoir, serves multiple purposes including fire protection, livestock watering, and supporting small fish populations.


°F

°F

mph

Wind

%

Humidity

Summary

Constructed in 2001 by the NRCS, this earth dam stands at a height of 26 feet and spans 458 feet in length, with a storage capacity of 120 acre-feet. Located in Eldon, Iowa, along the TR-Soap Creek, this dam is regulated by the Iowa Department of Natural Resources and undergoes regular inspections to ensure its safety and functionality.

Despite being classified as low hazard potential, Derby Dam poses a moderate risk due to its age and lack of a recent condition assessment. The spillway, with a width of 2 feet, is uncontrolled, and the dam is designed to handle a drainage area of 0.5 square miles. The surrounding area covers 5.9 acres, providing essential water resources while also posing a potential risk to downstream communities in the event of a breach. With no emergency action plan in place, the management of this dam should be closely monitored to mitigate any potential risks to the environment and public safety.

Owned by the local government, Derby Dam in Iowa represents a key water resource management structure in the state. With a primary focus on serving local agricultural and ecological needs, this dam plays a crucial role in ensuring water availability for firefighting and livestock while also supporting biodiversity in the area. Going forward, continued monitoring and maintenance of Derby Dam will be essential to uphold its integrity and safeguard the surrounding communities and ecosystems from any potential threats or hazards.

Year Completed

2001

Dam Length

458

Dam Height

26

River Or Stream

TR- SOAP CREEK

Primary Dam Type

Earth

Surface Area

5.9

Drainage Area

0.5

Nid Storage

120

Hazard Potential

Low

Foundations

Soil

Nid Height

26
       
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.