In 1960, in order to prevent soil erosion, a bosa-dam (dam for preventing soil erosion), Ashio Dam (also known as Misawa Goryu Dam, literally, Misawa Meeting Dam) was built in Ashio-machi.
土砂の流出を防ぐため、1960年、足尾町に防砂ダムの足尾ダム（通称、三沢合流ダム）が作られた。