Even though the available number of potential hydropower sites is  limited by geography, and in the US the most viable sites have already been developed, recent dam proposals have sought to take advantage of common misconceptions about hydropower in an attempt to downplay the environmental impact of building a dam. This paper details the environmental footprint of dams, including those described as "small","incremental", "run-of-river" and "micro" hydro projects.

"Small" usually describes the energy capacity of a dam, rather than size.  For example, Washington State's 125 foot Condit Dam on the White Salmon is described as a "small" dam, as is the 210 foot Glines Canyon Dam (on the Elwha River also in Washington).  Maine's Edwards Dam was 917 feet wide but considered small.  All of these have been, or are facing removal due to enviromental and economic concerns. 

The paper documents the environmental impacts from dams regardless of size, discusses the problems associated with federal subsidies for new dams, and explores how dams will compound the environmental impacts of climate change.