Site 19 Souhegan Reservoir Report
Last Updated: December 16, 2025
Located in High Bridge, Hillsborough, New Hampshire, Site 19 Souhegan, also known as Site 19 Floodwater Dam, is a state-owned earth dam designed by the USDA NRCS in 1963 for the primary purpose of flood risk reduction along the Souhegan River.
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Summary
With a dam height of 35 feet and a length of 725 feet, this structure provides a maximum storage capacity of 2,238 acre-feet and serves a drainage area of 11.37 square miles. Despite being regulated by the NHDES WD, this dam is not subject to state permitting, inspection, or enforcement.
The dam's spillway, with an uncontrolled design and a width of 460 feet, can accommodate a maximum discharge of 18,577 cubic feet per second. However, its hazard potential is rated as high, indicating potential risks in the event of a significant flood event. The condition assessment of Site 19 Souhegan is currently listed as "Not Rated," with the last inspection conducted in August 2014. While the risk assessment is moderate, with a rating of 3, there is no detailed risk management plan or inundation maps prepared for this dam.
Despite its critical role in flood risk reduction, Site 19 Souhegan presents challenges in terms of its maintenance and emergency preparedness. With a high hazard potential and limited regulatory oversight, there is a need for increased monitoring and risk management measures to ensure the safety and effectiveness of this earth dam in protecting the surrounding community and environment from potential flooding events along the Souhegan River.
Year Completed |
1963 |
Dam Length |
725 |
Dam Height |
35 |
River Or Stream |
SOUHEGAN RIVER |
Primary Dam Type |
Earth |
Surface Area |
27 |
Hydraulic Height |
35 |
Drainage Area |
11.37 |
Nid Storage |
2238 |
Outlet Gates |
None |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
35 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Site 19 Souhegan
Grassy Pond boat launch