Byllesby Reservoir Report

Last Updated: December 5, 2025

Byllesby, a gravity dam located in Virginia's Carroll County, stands as a testament to the intersection of hydroelectric power and recreational opportunities.


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Summary

Completed in 1912, this multi-arch concrete structure spans 970 feet and reaches a height of 63 feet, providing a storage capacity of 2034 acre-feet. The dam's primary purpose is hydroelectric power generation, with a secondary focus on recreation, offering visitors a chance to enjoy the scenic beauty of the New River.

Managed by the Federal Energy Regulatory Commission, Byllesby Dam boasts a controlled spillway width of 656 feet and a maximum discharge capacity of 436,000 cubic feet per second. With a hazard potential rated as high and a risk assessment indicating a very high risk level, the dam's safety and emergency preparedness measures are crucial. While the condition assessment is not available, regular inspections ensure the integrity of this vital water resource infrastructure. Overall, Byllesby Dam is a key player in meeting Virginia's energy needs while offering a picturesque backdrop for outdoor enthusiasts and climate advocates alike.

Year Completed

1912

Dam Length

970

Dam Height

47

River Or Stream

New River

Primary Dam Type

Gravity

Surface Area

242

Hydraulic Height

56

Drainage Area

1310

Nid Storage

2034

Structural Height

63

Outlet Gates

Other Controlled - 1, Tainter (radial) - 6

Hazard Potential

High

Foundations

Rock

Nid Height

63
       
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.