Watchung Square Dam Reservoir Report

Last Updated: December 7, 2025

Watchung Square Dam, located in N.


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Summary

Plainfield, New Jersey, is a private dam that plays a crucial role in flood risk reduction along the Green Brook. Standing at a height of 9.5 feet with a length of 600 feet, this earth dam provides a storage capacity of 11 acre-feet and a maximum discharge of 750 cubic feet per second. Despite its significant hazard potential, the dam is in satisfactory condition, as indicated by its last inspection in May 2021.

Managed by the New Jersey Department of Environmental Protection (NJDEP), Watchung Square Dam is subject to state regulation, permitting, inspection, and enforcement to ensure its structural integrity and operational safety. The dam serves as a vital infrastructure for flood control in the region, contributing to the overall resilience of the area against potential water-related disasters. With its primary purpose being flood risk reduction, the dam continues to play a critical role in protecting the community and surrounding areas from the impacts of extreme weather events and climate change.

As climate change amplifies the frequency and intensity of precipitation events, dams like Watchung Square Dam become increasingly important in safeguarding communities against flooding and water-related hazards. Ongoing monitoring, maintenance, and adherence to regulatory standards are essential to ensure the continued effectiveness and safety of this vital water resource infrastructure in Somerset County, New Jersey.

Dam Length

600

Dam Height

9.5

River Or Stream

Green Brook

Primary Dam Type

Earth

Surface Area

1

Drainage Area

0.06

Nid Storage

11

Hazard Potential

Significant

Nid Height

10
       
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.