Lewisville Dam Reservoir Report

Last Updated: December 5, 2025

Lewisville Dam, located in Denton, Texas, along the Elm Fork of the Trinity River, serves as a crucial flood risk reduction infrastructure designed by the US Army Corps of Engineers.


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Summary

Completed in 1955, the dam stands at 130 feet high and spans 32,328 feet in length, with a primary purpose of flood risk reduction. Despite its effectiveness in reducing downstream flooding, a risk assessment conducted in October 2014 identified the dam as having a high hazard potential, particularly during extreme flood events that could lead to a breach or large flows over the spillway, impacting communities downstream such as Lewisville, Coppell, Carrollton, Farmers Branch, Irving, and Dallas.

To address the identified deficiencies and reduce the risk associated with the dam, the US Army Corps of Engineers has implemented various risk management measures. These include working closely with local emergency managers to develop evacuation plans, regularly updating the emergency action plan, conducting emergency exercises, and ongoing inspections and maintenance of the dam. Furthermore, construction is underway for dam safety modifications, such as building a downstream inverted filter berm, anchoring the spillway weir, and constructing a barrier wall downstream of the spillway to enhance the dam's structural integrity and reduce the risk of failure. Despite the remote probability of failure, efforts are ongoing to safeguard the dam and surrounding communities from potential catastrophic impacts.

Year Completed

1955

Dam Length

32328

Dam Height

130

River Or Stream

ELM FORK OF THE TRINITY RIVER

Primary Dam Type

Earth

Surface Area

23280

Hydraulic Height

118

Drainage Area

1660

Nid Storage

1804300

Structural Height

135

Outlet Gates

Uncontrolled - 0

Hazard Potential

High

Foundations

Soil

Nid Height

135
       
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.