Upper Big Nemaha 11-a
Upper Big Nemaha 11-a is an earth dam located in Lancaster County, Nebraska, built in 1971. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Upper Big Nemaha 11-a
The primary purpose of Upper Big Nemaha 11-a is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Nemaha Natural Resources District (local government). It impounds the Tr-mid Br Big Nemaha River near Firth.
The dam stands 38 feet tall and stretches 974 feet across, creates a reservoir covering 25 acres, has a maximum storage capacity of 1,148 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1971, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 06/27/2023.
At 38 feet, this dam is taller than 85% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Nebraska dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Nebraska |
| County | Lancaster |
| Nearest City | Firth |
| River/Stream | Tr-mid Br Big Nemaha River |
| Coordinates | 40.53392, -96.60060 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 38 ft |
| Dam Height | 36 ft |
| Dam Length | 974 ft |
| Year Completed | 1971 (55 years old) |
Storage & Hydraulics
| NID Storage | 1,148 acre-ft |
| Max Storage | 1,148 acre-ft |
| Normal Storage | 125 acre-ft |
| Surface Area | 25 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 8,500 cfs |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Nemaha Natural Resources District |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/27/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NE00550 |
| Federal ID | NE00550 |
| More Info | State Dam Safety Program |