Dd No 21, located in Brown County, Kansas, is a local government-owned earth dam designed by King Engineering to primarily reduce flood risk along the Pony Creek-TR. Completed in 2003, this dam stands at a height of 33 feet and has a length of 1100 feet, providing a storage capacity of 377 acre-feet. With a spillway width of 40 feet and uncontrolled spillway type, Dd No 21 has been assessed as having a low hazard potential and a moderate risk level.

Managed by the Kansas Department of Agriculture, this dam is regulated, permitted, inspected, and enforced by the state agency to ensure its structural integrity and safety. The last inspection in October 2019 deemed the dam's condition as not rated, and there are no emergency action plans (EAP) prepared or updated for this structure. Despite its relatively low hazard potential, the risk assessment for Dd No 21 indicates a moderate risk level (3), prompting the need for continued risk management measures and vigilance in monitoring its performance during extreme weather events.

Water resource and climate enthusiasts interested in the impact of dams on flood risk reduction and water storage in Kansas can find Dd No 21 as a noteworthy case study. With its strategic location along the Pony Creek-TR and its significant storage capacity, this earth dam serves as a crucial infrastructure for managing water flow and mitigating flood risks in the region. Continued monitoring and maintenance of this dam by state regulatory agencies are essential to ensure its effectiveness in safeguarding the local community from potential flooding events.