Salmonid Spawning Habitat in Rivers: Physical Controls, Biological Responses, and Approaches to Remediation
Evaluating Changes in Salmon Spawning Habitat and Spawners in the Elwha River Following Dam Removal
Phil Roni, Mike McHenry, George Pess, and Tim Beechie
More than 76,000 dams greater than 2 m in height have been constructed in the United States (USACOE 1996; Pohl 2002). By the year 2020, more than 80% of these dams will reach the end of their useful lives (Stanley and Doyle 2003). Dams have been implicated as a primary cause in the decline of native fish fauna, including populations of Pacific Northwest salmonids listed under the Endangered Species Act (Myers et al. 1998). The removal of aging and inefficient dams is now considered a viable river management and salmon restoration alternative in the United States (American Rivers 1999; Stanley and Doyle 2003). Approximately 500 dams have been removed in the United States over the past two decades, and the rate of removal is clearly accelerating (Pohl 2002; Graf 2005). Case studies examining the effects of removing small dams (<30 m in height) are increasingly common (Stanley and Doyle 2003), though the majority of dam removal studies are from small impoundments in the Midwest on glacial landforms with low relief (Graf 2005; Doyle et al. 2005). Removal of a large high dam blocking access of anadromous salmon populations has not occurred or been evaluated.