Upper Big Nemaha 20-B is a local government-owned earth dam located in Johnson, Nebraska, along the TR-N FK Big Nemaha River.
Wind
Humidity
Designed by USDA NRCS and completed in 1973, this dam serves the primary purpose of flood risk reduction in the area. With a height of 38 feet and a length of 1127 feet, it has a storage capacity of 430 acre-feet and covers a surface area of 24 acres, providing protection for a drainage area of 1.1 square miles.
Managed by the Nebraska Department of Natural Resources, Upper Big Nemaha 20-B has a low hazard potential and is in fair condition as of the last assessment in June 2016. The dam has a structural height of 42 feet and a hydraulic height of 36 feet, with a maximum discharge capacity of 939 cubic feet per second. While no spillway type is specified, the dam's condition is regularly inspected every five years to ensure its continued effectiveness in mitigating flood risks in the region.
Located in a rural setting, Upper Big Nemaha 20-B plays a crucial role in protecting the surrounding area from potential flooding events, highlighting the importance of proper dam infrastructure for water resource and climate management. With its strategic placement along the river and state-regulated operations, this dam stands as a testament to the collaborative efforts between local government entities and federal agencies in ensuring the safety and resilience of communities in Nebraska.
Year Completed |
1973 |
Dam Length |
1127 |
Dam Height |
38 |
River Or Stream |
TR-N FK BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
24 |
Hydraulic Height |
36 |
Drainage Area |
1.1 |
Nid Storage |
430 |
Structural Height |
42 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
42 |