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Riparian Habitat

Historic

Based on a visual estimate of landscape cover types depicted in a reconstruction of land survey records from 1851-1865, the small segment of riparian area along the Willamette River in the this subwatershed pre-1850 consisted of an ash-willow wetland forest (Hulse et al., 2002).

The landscape cover types depicted in the reconstruction of land survey records from 1851-1865 show that the riparian areas along Stephens Creek were closed-canopy forest for the 300-foot riparian width and beyond for the lower 50 percent of the creek (Hulse et al., 2002). Riparian areas associated with Stephens Creek were likely extensive and probably supported a diversity of species. Snags and downed wood were likely abundant.

Current

Based on a visual estimate of 2002 aerial photography, the Willamette River riparian area consists of forested wetland at the mouth of Stephens Creek. The riparian vegetation extends from the Willamette to Macadam Avenue. Trees in the riparian forest vary in age from 30 and 80 years (City of Portland Bureau of Planning, 2000).

The riparian area of Stephens Creek and its tributary streams consist of a total of 40% tree and shrub cover and 60% developed or cleared land. Riparian widths vary from 100 to 300 feet on the lower section of Stephens Creek to less than 100 feet or nonexistent in the upper subwatershed. The understory of the Stephens Creek riparian habitat is dominated by English ivy in many areas (City of Portland Bureau of Planning, 2000).

Assessment

Processes that have led to alterations to riparian habitat conditions include upstream development/vegetation removal (resulting in increased flows and sedimentation), road construction, and introduction of invasive plant species.

Riparian composition along the Willamette River in this subwatershed has remained relatively consistent over time. The riparian zone is still forested upland and wetland, although some development has occurred at the edges of the subwatershed boundary and non-native species are invading.
Maps & Files

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