Dd No 4a is a local government-owned dam located in McPherson, Kansas, along the Little Arkansas River. Designed by Booker/Freund, this Earth-type dam stands at a height of 27 feet and has a length of 2500 feet. Its primary purpose is flood risk reduction, with a storage capacity of 1411 acre-feet and a drainage area of 3.17 square miles.

The dam has a low hazard potential and is currently not rated for its condition assessment. It has a moderate risk level and is regulated by the Kansas Department of Agriculture. With a spillway width of 40 feet and a maximum discharge of 1260 cubic feet per second, Dd No 4a plays a crucial role in managing floodwaters and protecting the surrounding area from potential inundation.

Overall, Dd No 4a serves as an essential infrastructure for flood control in the region, with its strategic location along the Little Arkansas River. While it has not been inspected recently, its design and purpose highlight the importance of water resource management in mitigating potential risks and ensuring the safety of nearby communities.