Lopez Dam Reservoir Report

Last Updated: December 5, 2025

Lopez Dam, also known as Lopez Reservoir, is a federal-owned structure located in Los Angeles, California.


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Summary

Completed in 1954, the dam's primary purpose is debris control, with the additional benefit of flood risk reduction. Standing at a height of 50 feet with a hydraulic height of 44 feet, the dam has a storage capacity of 209 acre-feet and a maximum discharge of 32,000 cubic feet per second. It spans 1,300 feet across the Pacoima Wash, serving as a vital component of water resource management in the region.

Despite being classified as high risk in a 2009 assessment by the US Army Corps of Engineers (USACE), efforts are in place to mitigate potential hazards associated with the dam. USACE actively engages with state and local emergency managers, conducts emergency exercises, and closely monitors rainfall forecasts to provide timely flood warnings. Continuous inspections, monitoring, maintenance, and repair work are conducted to ensure the dam's structural integrity and performance. Risk communication activities, including updates to the Emergency Action Plan and coordination with first responders, are also ongoing. Further studies of the dam are planned for 2023 to enhance its safety and resilience for the surrounding urbanized and densely populated areas of Los Angeles and San Fernando, California.

Year Completed

1954

Dam Length

1300

Dam Height

50

River Or Stream

PACOIMA WASH

Primary Dam Type

Earth

Surface Area

1

Hydraulic Height

44

Drainage Area

34

Nid Storage

209

Outlet Gates

None - 0

Hazard Potential

High

Nid Height

50
       
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.