Section 16(b) of the Act defines free-flowing as “existing or flowing in a natural condition without impoundment, diversion, straightening, rip-rapping, or other modification of the waterway. The existence, however, of low dams, diversion works and other minor structures at the time any river is proposed for inclusion in the national wild and scenic rivers system shall not automatically bar its consideration for such inclusion: Provided, that this shall not be construed to authorize, intend, or encourage future construction of such structures in components of the national wild and scenic rivers system.”
The existence of small dams, diversion works, or other minor in-channel structures shall not automatically disqualify a river as a potential addition to the National System. Congress did not intend all rivers to be “naturally flowing,” i.e., flowing without any manmade up- or downstream manipulation. The presence of impoundments above and/or below the segment (including those which may regulate flow within the segment), and existing minor dams or diversion structures within the study area, do not necessarily render a river segment ineligible. There are segments in the National Wild & Scenic Rivers System that are downstream from major dams or are located between dams.