Soap Creek Watershed Site 90-74 Reservoir Report

Last Updated: December 6, 2025

Soap Creek Watershed Site 90-74 is a flood risk reduction structure located in Selma, Iowa, within the Tr-Brush Creek watershed.


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Summary

Constructed in 2006 by the USDA NRCS, this earth dam stands at a height of 31 feet and spans 625 feet in length, providing a storage capacity of 83 acre-feet. With a low hazard potential and a moderate risk assessment rating, this dam plays a crucial role in mitigating the risk of floods in the area.

Managed by the local government and regulated by the Iowa DNR, Soap Creek Watershed Site 90-74 is designed to handle a maximum discharge of 108 cubic feet per second through an uncontrolled spillway. The dam serves the primary purpose of flood risk reduction, with a normal storage capacity of 23 acre-feet and a drainage area of 0.33 square miles. Despite not being condition rated, this structure aligns with state permitting and inspection requirements, ensuring its effectiveness in protecting the surrounding community from potential flood events.

With a strategic location in Wapello County, Iowa, Soap Creek Watershed Site 90-74 provides critical flood protection for the residents of Selma. As a key component of the local water resource management system, this dam exemplifies the collaborative efforts between federal and state agencies to safeguard communities against the impacts of climate change. Its design, construction, and operational standards reflect a commitment to resilience and sustainability in the face of changing environmental conditions.

Year Completed

2006

Dam Length

625

Dam Height

31

River Or Stream

Tr-Brush Creek

Primary Dam Type

Earth

Surface Area

4

Drainage Area

0.33

Nid Storage

83

Hazard Potential

Low

Foundations

Soil

Nid Height

31
       
Seasonal Comparison

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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.