Lake Isabella Dam Reservoir Report

Last Updated: December 5, 2025

Lake Isabella Dam, located in Mount Pleasant, Michigan, is a privately owned structure that serves primarily for recreation purposes.


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Summary

Built in 1967, this earth dam stands at 41 feet in height and spans a length of 3010 feet, creating a reservoir with a maximum storage capacity of 13,500 acre-feet. The dam overlooks the Chippewa River, with a drainage area of 416 square miles and a surface area of 730 acres.

With a high hazard potential but a satisfactory condition assessment as of July 2019, Lake Isabella Dam is regulated and inspected by the Michigan Department of Environment, Great Lakes, and Energy. The dam features an uncontrolled spillway with a width of 130 feet and a maximum discharge capacity of 11,600 cubic feet per second. Despite its moderate risk assessment, there are no associated lock structures or outlet gates present. The dam's Emergency Action Plan was last revised in 2008, and the overall risk management measures and guidelines are yet to be specified.

Situated in Isabella County, Lake Isabella Dam not only provides recreational opportunities for the local community but also plays a crucial role in flood control and water resource management. As a significant component of the region's infrastructure, ongoing monitoring and adherence to safety protocols are essential to ensure the continued integrity and functionality of this vital water resource structure.

Year Completed

1967

Dam Length

3010

Dam Height

41

River Or Stream

Chippewa River

Primary Dam Type

Earth

Surface Area

730

Hydraulic Height

38.5

Drainage Area

416

Nid Storage

13500

Structural Height

41

Hazard Potential

High

Nid Height

41
       
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.