Upper Big Nemaha L-4
Upper Big Nemaha L-4 is an earth dam located in Lancaster County, Nebraska, built in 1971. It carries a Significant hazard potential classification and has a poor condition assessment.
About Upper Big Nemaha L-4
The primary purpose of Upper Big Nemaha L-4 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 26 feet tall and stretches 700 feet across, creates a reservoir covering 15 acres, has a maximum storage capacity of 371 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1971, the structure is well into its service life at over 50 years old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 04/19/2023.
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Location
| State | Nebraska |
| County | Lancaster |
| Nearest City | Firth |
| River/Stream | Tr-mid Br Big Nemaha River |
| Coordinates | 40.54762, -96.58717 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 26 ft |
| Dam Height | 25 ft |
| Dam Length | 700 ft |
| Year Completed | 1971 (55 years old) |
Storage & Hydraulics
| NID Storage | 371 acre-ft |
| Max Storage | 371 acre-ft |
| Normal Storage | 64 acre-ft |
| Surface Area | 15 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 6,384 cfs |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Nemaha Natural Resources District |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 04/19/2023 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | NE00549 |
| Federal ID | NE00549 |
| More Info | State Dam Safety Program |