Lake Shawnee Dam Reservoir Report

Last Updated: December 9, 2025

Lake Shawnee Dam in Morris, New Jersey, stands as a significant recreational resource along the Weldon Brook, offering a surface area of 79 acres and a maximum storage capacity of 376 acre-feet.


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Summary

Despite its primary purpose for recreation, the dam's poor condition assessment and significant hazard potential raise concerns for its long-term safety and maintenance.

With a height of 9 feet and a length of 150 feet, Lake Shawnee Dam presents a gravity earth structure that requires regular state inspections and enforcement to ensure public safety. The dam's location in Jefferson Township adds to its importance as a vital water resource for the surrounding area, with a drainage area of 7.6 square miles and a maximum discharge capacity of 522 cubic feet per second.

As water resource and climate enthusiasts continue to monitor Lake Shawnee Dam's condition, it becomes evident that proactive risk management measures and emergency action plans are essential to mitigate potential hazards and safeguard the dam's integrity for future generations. The collaboration between state regulatory agencies and private owners will be crucial in addressing the dam's maintenance needs and ensuring its continued safe operation in the years to come.

Dam Length

150

Dam Height

9

River Or Stream

Weldon Brook

Primary Dam Type

Earth

Surface Area

79

Drainage Area

7.6

Nid Storage

376

Hazard Potential

Significant

Nid Height

9
       
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.