Johnson (Oscar) Dam, located in Harrison County, Iowa, is a private-owned structure designed by the USDA NRCS and completed in 2011. The dam serves multiple purposes, including flood risk reduction, grade stabilization, and recreation. It has a dam height of 49 feet and a length of 530 feet, with a storage capacity of 187 acre-feet and a drainage area of 0.75 square miles.

Managed by the Iowa Department of Natural Resources, Johnson Dam is regulated, permitted, and inspected by state authorities to ensure its safety and functionality. Despite being classified as a low-hazard structure with a "Not Rated" condition assessment, the dam plays a crucial role in protecting the surrounding area from potential flooding events. Situated on a tributary to Elk Creek, the dam also provides habitat for fish and wildlife, making it a valuable resource for conservation efforts in the region.

With its strategic location in Missouri Valley and its contribution to flood risk reduction, Johnson (Oscar) Dam stands as a vital infrastructure project in Iowa. Its construction and operation are supported by federal funding from the Natural Resources Conservation Service, highlighting the collaboration between private and government entities to manage water resources and enhance environmental sustainability. As a key piece of the state's water management infrastructure, the dam reflects a commitment to resilience and safety in the face of climate challenges.