Mcmahan Lake Dam Reservoir Report

Last Updated: December 5, 2025

Mcmahan Lake Dam, located in Sebastian County, Arkansas, serves as a recreational spot for water resource and climate enthusiasts.


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Summary

Completed in 1948, this earth dam stands at a height of 11.1 feet and has a hydraulic height of 7.3 feet. With a storage capacity of 43 acre-feet, the dam provides a surface area of 5.6 acres for outdoor activities such as fishing and boating on Little Grasse Creek.

Despite its primary purpose for recreation, Mcmahan Lake Dam poses a significant hazard potential due to its age and lack of recent inspections. The dam has not been rated for its condition assessment, and the last inspection dates back to June 1981. With no emergency action plan in place and limited information on risk management measures, there is a need for increased attention to ensure the safety and integrity of this structure.

As water enthusiasts continue to enjoy the picturesque setting of Mcmahan Lake Dam, it is crucial for relevant authorities to prioritize regular inspections, assess its condition, and develop appropriate emergency response plans. By addressing these concerns and implementing necessary risk management measures, the dam can continue to provide a safe and enjoyable environment for outdoor recreation activities in the region.

Year Completed

1948

Dam Length

811.1

Dam Height

11.1

River Or Stream

LITTLE GRASSE CREEK-TR

Primary Dam Type

Earth

Surface Area

5.6

Hydraulic Height

7.3

Drainage Area

0.31

Nid Storage

43

Hazard Potential

Significant

Nid Height

11
       
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.