Lake Cohasset Lower Dam Reservoir Report

Last Updated: December 6, 2025

Located in Orange County, New York, the Lake Cohasset Lower Dam stands as a testament to engineering prowess, completed in 1924 to serve as a recreational water resource for the surrounding area.


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Summary

With a concrete structure standing at 21 feet high and 330 feet long, the dam holds a storage capacity of 84 acre-feet, providing essential water for the 12-acre surface area of Lake Cohasset. This vital infrastructure on Arden Brook is regulated and inspected by the New York State Department of Environmental Conservation, ensuring the safety and sustainability of the dam.

Despite its fair condition assessment and high hazard potential, the Lake Cohasset Lower Dam remains a beloved site for water and climate enthusiasts, offering opportunities for recreation and outdoor activities in the scenic surroundings of Arden, New York. The dam's uncontrolled spillway, 122 feet wide, adds to its allure as a natural marvel, attracting visitors to witness the controlled release of water during times of high discharge. With a moderate risk assessment rating and a history of regular inspections, the dam continues to serve its primary purpose of providing a tranquil setting for locals and visitors alike to enjoy the beauty of nature.

For those interested in water resource management and climate resilience, the Lake Cohasset Lower Dam presents a case study in balancing recreational needs with safety and environmental concerns. As a state-regulated structure with a history dating back nearly a century, the dam symbolizes the importance of maintaining and monitoring critical infrastructure to ensure its longevity and functionality in the face of changing climatic conditions. With a dedicated state agency overseeing its operations, inspections, and enforcement, the Lake Cohasset Lower Dam serves as a model for responsible dam management in the pursuit of sustainable water resource utilization.

Year Completed

1924

Dam Length

330

Dam Height

21

River Or Stream

ARDEN BROOK

Primary Dam Type

Concrete

Surface Area

12

Drainage Area

1.49

Nid Storage

84

Hazard Potential

High

Nid Height

21
       
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.