Dams and other man-made obstacles to fish passage fragment riverine habitats and re-structure fish communities. Many of these structures provide no means of fish passage or only partial passage for a few species. This is particularly problematic for diadromous and potamodromous species that must move between rearing, feeding, and spawning habitats to complete their normal life cycle. In the United States and in Europe, many of these structures have become obsolete, and as a consequence, dam removal has become a feasible fish restoration solution in many areas (Jackson and Moser 2012, Hogg et al.
2013, Jolley et al. 2013, Lasne et al. 2015). In the northwestern corner of Washington state, the Elwha Dam, a 32-m high hydroelectric facility, was constructed during 1910–1913 on the Elwha River at rkm 7.9 (Duda et al. 2011, Figures 1 and 2). In 1925, the 64-m high Glines Canyon Dam was built at Elwha rkm 21.6 (Figures 1 and 2). These dams were constructed with no regard for local and tribal concerns regarding fish passage (Valadez 2003) and included no provisions for passage of salmon or other fish species. Consequently, the dams completely blocked access to over 90% of the anadromous fish spawning and rearing habitat in this pristine drainage (Valadez 2003).