Portland State University. Department of Geography.
Teresa L. Bulman
Date of Publication
Master of Science (M.S.) in Geography
Riparian ecology -- Oregon -- Johnson Creek, Salmonidae -- Habitat -- Oregon -- Johnson Creek, Nature -- Effect of human beings on -- Oregon -- Johnson Creek
1 online resource (2, viii, 118 p.)
Pacific salmon populations in Johnson Creek, Portland, Oregon have been adversely impacted by urbanization, and by residential and agricultural land development. f Ecological impacts include loss or depletion of riparian vegetation features which directly influence stream and associated salmonid ecology. This research examines the nearstream riparian zone's contribution to instream habitat complexity for anadromous salmonids in Johnson Creek. Visual surveys were conducted on over half the stream length. Five features were assessed to determine the extent of riparian influenced stream habitat including, overhead enclosure, overhanging vegetation, undercut banks, and large and small woody debris and root wads. The stream survey showed that areas of riparian-influenced habitat are spatially intermittent and present in areas of the least stream disturbance. Suitable riparian habitat is limited to locations where there is minimal riparian disturbance, property management, and channelization. I Although salmonid populations have been reduced, insufficient riparian influenced salmonid habitat features are not the primary limiting factor on salmon populations. Other factors such as pollution, sedimentation, hatchery fish introduction, low flows, inadequate food supplies, high stream temperatures, repress wild salmon populations.
Gude, Andrew Greiff, "An Assessment of the Riparian-influenced Salmonid Habitat Features of Johnson Creek, Portland, Oregon" (1994). Dissertations and Theses. Paper 5232.
Plate 1. Zoning map showing areas of diverse land use in the Johnson Creek Basin (City of Portland 1992b, 12).
Gude_Plate2.png (138 kB)
Plate 2. Water quality problems in Johnson Creek Basin (City of Portland 1992b, 16).
Gude_Plate3.png (101628 kB)
Plate 3. The three reaches and nine surveyed sections. The consecutive numbers along the creek indicate river miles (Adapted from U.S. Geological Survey topographical maps for Lake Oswego, Gladstone, Damascus, 1984; and Sandy 1985).
Plate4.TIF (345404 kB)
Plate 4. Location of the Springwater Corridor Trail and areas of significant habitat along Johnson Creek (City of Portland 1992e).