Lake Thornhill Dam Reservoir Report

Last Updated: December 6, 2025

Lake Thornhill Dam, located in Pearl River, Mississippi, is a privately owned earth dam primarily used for recreation.


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Summary

Constructed in 2004 by Simmons Consulting Engineers, this dam stands at a height of 24 feet with a hydraulic height of 19 feet and a structural height of 28 feet. It has a storage capacity of 440 acre-feet, with a normal storage level of 275 acre-feet, covering a surface area of 55 acres and serving a drainage area of 1.07 square miles.

With a low hazard potential and a satisfactory condition assessment, Lake Thornhill Dam is regulated and inspected by the Mississippi Department of Environmental Quality. Despite its uncontrolled spillway type, the dam has a maximum discharge capacity of 1867.5 cubic feet per second, ensuring adequate safety measures. The risk assessment for this dam is moderate, indicating that appropriate risk management measures are in place to mitigate potential hazards.

Lake Thornhill Dam offers a serene recreational environment for water resource and climate enthusiasts to enjoy, providing opportunities for fishing, boating, and other water-based activities. Its picturesque location along the UNT of Davis Creek, under the jurisdiction of the Mobile District, makes it a popular destination for outdoor enthusiasts seeking a tranquil escape in the heart of Mississippi's natural beauty.

Year Completed

2004

Dam Length

1450

Dam Height

24

River Or Stream

UNT OF DAVIS CREEK

Primary Dam Type

Earth

Surface Area

55

Hydraulic Height

19

Drainage Area

1.07

Nid Storage

440

Structural Height

28

Hazard Potential

Low

Nid Height

28
       
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.