Windy Hill Subwatershed Site 3a-1, located in Woodbury County, Iowa, is a local government-owned earth dam completed in 1975 by the USDA NRCS. This dam serves multiple purposes including fire protection, stock, small fish pond, and flood risk reduction for the surrounding area. With a height of 34 feet and a length of 520 feet, it has a storage capacity of 107 acre-feet and covers a surface area of 6 acres.

The dam is regulated by the Iowa DNR and is in good condition with a low hazard potential. Its risk assessment is moderate, indicating a need for ongoing monitoring and management measures. Despite its uncontrolled spillway type, the dam has not experienced any major issues or modifications since its completion. The structure sits along the TR-West Fork Little Sioux river, contributing to the overall water resource management in the region.

Overall, Windy Hill Subwatershed Site 3a-1 plays a crucial role in ensuring water availability and flood protection in the Rolly Springs area. With its multiple functions and regulated status, it serves as a valuable asset for both the local community and the broader ecosystem. Ongoing inspections and risk assessments will be important to maintain the dam's effectiveness and safety in the face of changing climate conditions.