Upper Big Nemaha G-18 is a local government-owned dam located in Lancaster, Nebraska, with a primary purpose of flood risk reduction. Built in 1977 by the USDA NRCS, this earth dam stands at 25 feet tall and stretches 750 feet in length, providing a storage capacity of 189 acre-feet. Situated along the TR-Mid Br Big Nemaha River, the dam's low hazard potential and satisfactory condition assessment make it a vital infrastructure for managing water resources in the area.

Managed by the Nebraska Department of Natural Resources, Upper Big Nemaha G-18 is subject to state regulation, permitting, inspection, and enforcement. With a drainage area of 0.7 square miles and a maximum discharge capability of 339 cubic feet per second, the dam plays a crucial role in protecting the surrounding area from potential flooding events. Its stone core and soil foundation contribute to its structural integrity, while its location in Firth, Nebraska, underscores its importance for flood control and water resource management in the region.

Despite its low hazard potential, Upper Big Nemaha G-18 remains a key component of the local flood control infrastructure, with regular inspections and a satisfactory condition assessment ensuring its continued functionality. As climate change impacts increase the frequency and intensity of extreme weather events, the dam's role in mitigating flood risks and protecting the community underscores the importance of proactive water resource management and infrastructure maintenance.