St Marys River Watershed Site 1 Reservoir Report

Last Updated: December 25, 2025

Located in St.


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Summary

Mary's County, Maryland, St Marys River Watershed Site 1, also known as St Marys River State Park Dam, is a crucial flood risk reduction structure designed by Allan Stahl of the USDA NRCS. Completed in 1975, this earth dam stands at a height of 38 feet and spans 1670 feet, serving as a vital component in managing water flow along the Western Branch of the St. Marys River.

With a normal storage capacity of 3200 acre-feet and a maximum discharge of 20576 cubic feet per second, this dam plays a significant role in protecting the surrounding area from flooding while also providing recreational opportunities for the local community. However, recent assessments have indicated a poor condition of the dam, with a high hazard potential and a moderate risk level, making regular inspections and maintenance crucial for ensuring its continued effectiveness.

In addition to flood risk reduction, St Marys River Watershed Site 1 is also regulated by the Maryland Dam Safety agency, reflecting the state's commitment to ensuring the safety and functionality of its water infrastructure. As climate change continues to impact water resources, the maintenance and proper management of dams like this one become increasingly important in safeguarding communities and ecosystems against the threats of extreme weather events and rising water levels.

Year Completed

1975

Dam Length

1670

Dam Height

38

River Or Stream

Western Br, St. Marys River

Primary Dam Type

Earth

Surface Area

250

Drainage Area

8.8

Nid Storage

9600

Outlet Gates

Slide (sluice gate) - 0

Hazard Potential

High

Foundations

Soil

Nid Height

38
       
Seasonal Comparison

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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.