Rocky Branch Creek Watershed Site C-3a is a low hazard potential dam located in Jefferson, Iowa, owned by the local government and regulated by the Iowa Department of Natural Resources. This Earth dam, completed in 1969, serves multiple purposes including fire protection, stock, small fish pond, and flood risk reduction. With a maximum storage capacity of 12 acre-feet, it covers a surface area of 1 acre and drains a 0.09 square mile watershed.

Managed by the USDA NRCS, this dam on TR- Rocky Branch Creek has a moderate risk assessment rating and has not been rated for its condition. With a spillway type of uncontrolled, the dam has a height of 25 feet and is primarily used for water resource management in the area. While it has not been inspected recently, it is important to note that the dam's emergency action plan status, inundation maps, and risk management measures are currently unknown. Overall, Rocky Branch Creek Watershed Site C-3a provides critical water resource functions for the Rome community.