Upper Big Nemaha 15-A Reservoir Report
Last Updated: December 5, 2025
Upper Big Nemaha 15-A is a local government-owned earth dam located in Lancaster, Nebraska, designed by USDA NRCS to reduce flood risks along the TR-MID BR Big Nemaha River.
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Summary
The dam, completed in 1970, stands at a height of 20 feet and stretches 662 feet in length, with a storage capacity of 242 acre-feet. With a low hazard potential and satisfactory condition assessment, the dam is regulated and inspected by the Nebraska Department of Natural Resources, ensuring its structural integrity and functionality in mitigating flood risks for the surrounding area.
Situated in a rural landscape, Upper Big Nemaha 15-A plays a crucial role in protecting the local community from potential flooding events, with a maximum discharge capacity of 1402 cubic feet per second. The dam's primary purpose of flood risk reduction aligns with its design as an earth structure with stone core and soil foundation. The dam's normal storage capacity of 24 acre-feet covers a surface area of 8 acres, serving a drainage area of 0.6 square miles. Despite its modest size, Upper Big Nemaha 15-A serves as a vital infrastructure for flood control and water resource management within the region.
With its last inspection conducted in 2016, Upper Big Nemaha 15-A has demonstrated satisfactory performance and adherence to safety guidelines, ensuring its readiness to handle emergency situations. Although no Emergency Action Plan (EAP) is reported, the dam's low hazard potential and continuous monitoring by regulatory agencies enhance its resilience to potential risks. As a valuable asset in the area's water resource and climate resilience efforts, Upper Big Nemaha 15-A stands as a testament to effective collaboration between local government, federal agencies, and engineering expertise in safeguarding communities against natural disasters.
Year Completed |
1970 |
Dam Length |
662 |
Dam Height |
20 |
River Or Stream |
TR-MID BR BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
8 |
Hydraulic Height |
20 |
Drainage Area |
0.6 |
Nid Storage |
242 |
Structural Height |
24 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
24 |
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.
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