Impacts of Power Line Rights-of-Way on Forested Stream Habitat in Western Washington

摘要

Pacific Salmon Oncorhynchus spp. have inhabited streams of the Pacific Northwest for millen-nia. In the past century, however, many populations have suffered severe declines and evenextinction, largely due to settlement of the West Coast. Hydroelectric dams, an artifact of indus-trialization, necessitate swaths through forests to extend powerlines from generating facilitiesto consumers. Rights-of-way are cleared of trees, and roads are built for equipment access. Manyrights-of-way that cross streams in forested areas cause disturbances to riparian zones. Salmonidsare sensitive to disturbances that lead to altered temperatures, lack of dissolved oxygen, and in-creased sedimentation. This project's objective was to quantify effects of rights-of-way on forestedstreams by comparing right-of-way and paired upstream habitat. Measurements included benthicmacroinvertebrates, canopy cover, fish presence, water quality, and percentage of fine particles(< 0.85 mm) in streambed gravel to determine suitability as spawning habitat. The only parame-ter that was significantly different was canopy cover with a mean of 29% in rights-of-way and75% upstream. The parameters were expected to show degradation in the right-of-way due toopened canopy and gravel roads. The results, however, do not confirm the hypotheses. Over-all, the elements show a decrease from ideal salmonid habitat conditions. It is likely that thestreams intersected by rights-of-way have recovered from the initial disturbances that occurred30 to 50 years ago, and have restabilized to a natural regime. It is also possible that any degrada-tion caused by rights-of-way is masked by wider scale disturbances such as timber harvest andoff-road vehicle activities