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University of Oregon North Campus Conditional Use Permit Project Riparian Assessment and Management Report 3.2.1Millrace Slough During the July 2017 field effort, the northern segment of the Millrace Slough (south of the confluence) was dominated by English ivy, with the majority of the riparian zone lacking a shrub layer. English ivy can exacerbate erosion issues because its shallow root system lacks the ability to provide the deep soil anchoring and bank stabilization provided by mature trees and shrubs. Excessive soil erosion control can cause excessive sediment runoff, reducing water quality, and can lead to streambank failure and degraded riparian conditions. In addition, its climbing vines can eventually kill large overstory trees which provide the necessary shade for reducing water temperature. English ivy provides very little habitat for native wildlife species and reduces the overall biodiversity of the riparian zone. The middle segment of the slough within the PSA provides improved habitat with a good mixture of tree, shrub, and herbaceous layers. However, the obstructed culvert on the south side of the bike path might restrict water from the Willamette River to flow freely into the slough, reducing flood storage. The southern segment of the slough at the railroad right-of-way near the Millrace Slough water control structure, contained little to no tree cover during the field effort. A lack of canopy cover may reduce shade, causing warmer water, and diminished habitat quality and species biodiversity. The composition of vegetation strata at each riparian assessment point is shown in Figure 4, Appendix A. 3.2.2Willamette River Riparian habitat throughout the Willamette River within the PSA was fairly uniform with steep banks and multilayered vegetation composition. The narrow riparian zone along the Willamette River displayed complex vegetation structure providing shade for aquatic and riparian species (Appendix B). In addition, this multilayered vegetation composition protects and stabilizes the river bank and reduces water velocity during high flows. The riparian zone of the Willamette River within the PSA was fairly steep, most likely a result of historic degradation of riparian functions and upstream flood control measures in place for the last 50-60 years. However, there are pockets of gently sloped streambank sections in the PSA that still provide intact riparian functions. There were pockets of Himalayan blackberry thickets observed within the riparian zone at the time of the July 2017 field effort. Figure 2 in Appendix A illustrates the general location of the larger infestations that result in decreased streambank stability and degraded riparian habitat conditions. 3.3Upland Habitat The upland habitat within the PSA has been historically used for mining, sand and gravel screening, concrete production, and utility pole storage, prior to the more recent, passive uses by UO (L.R. Squier Associates, Inc., 1990). This upland habitat is considered degraded or, in some areas marginal, due to these past land uses. The area has been converted to open fields used for recreation and educational purposes. As previously noted, a paved bike and pedestrian trail runs east-west within the PSA and there is a large access ramp south of the pedestrian bridge landscaped with ornamental shrubs. Well-established Himalayan blackberry patches are dispersed throughout the area, primarily adjacent to the riparian zone. The remaining open space contains a fenced field with possible seasonal wetlands, an irrigated recreational field, and a maintained area seeded with cultivar grasses. These habitat types are displayed in Appendix A, Figure 2. This upland habitat contains compacted soils from years of industrial use. However, due to the location adjacent to the Willamette River, the area still serves to support baseline floodplain functions such as groundwater recharge and flood storage. In addition, with the buildup of urban areas surrounding the PSA, this upland open space provides a movement corridor for wildlife. Ungulates and larger terrestrial species might utilize this open page 6