Hubbard Dam is a privately owned structure located in Diagonal, Iowa, that serves primarily for recreational purposes. Constructed in 1971 by the USDA NRCS, this earth dam stands at a height of 24 feet and spans a length of 416 feet, with a storage capacity of 65 acre-feet. Situated on TR-West Plum Creek, the dam's reservoir covers a surface area of 4.8 acres and has a drainage area of 0.26 square miles. Despite its low hazard potential, the dam is regulated and inspected by the Iowa Department of Natural Resources, ensuring its safety and compliance with state regulations.

With its uncontrolled spillway and soil foundation, Hubbard Dam presents a moderate risk level, as assessed by the authorities. While the dam's condition is currently not rated, it has not undergone any modifications since its completion. The emergency action plan status, including preparedness and risk management measures, remains unclear. The dam's location in Union County, Iowa, under the jurisdiction of the Rock Island District of the US Army Corps of Engineers, is represented by Congresswoman Cindy Axne. Water and climate enthusiasts may find Hubbard Dam to be an interesting case study in recreational dam infrastructure, showcasing the intersection of water resource management and environmental stewardship.