Amherst Twp 20 is a privately owned dam located in Fillmore County, Minnesota, specifically in the city of Houston. This dam, which is classified as a Rockfill type with a height of 17.8 feet, serves the primary purpose of flood risk reduction along the Root River South Fork. It has a storage capacity of 50.2 acre-feet and covers a drainage area of 1 square mile. Despite its low hazard potential, the dam is regulated, inspected, and enforced by the Minnesota Department of Natural Resources, ensuring its safety and effectiveness in managing floodwaters.

The dam at Amherst Twp 20 was last inspected in May 2018, with a regular inspection frequency of 8 years. While its condition assessment is currently listed as "Not Rated," the dam's emergency action plan status, risk assessment, and inundation maps are all marked as pending or unspecified. With no associated structures or federal agency involvement, this dam is solely managed by its private owner for flood risk reduction purposes. The presence of this structure contributes to the overall water resource management efforts in the area, showcasing the collaboration between private owners and state regulatory agencies to protect communities from potential flood hazards.