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University of Oregon North Campus Conditional Use Permit Project Riparian Assessment and Management Report and wildlife habitat. The degradation of any of these functions, singularly or cumulatively, can result in diminished riparian function. The following sections discuss the baseline riparian conditions within the PSA, relative to riparian functions listed in the paragraph above. 4.1Temperature and Shade The riparian plant community within the PSA’s riparian zone is characterized by both disturbed and relatively undisturbed habitats. Vegetation within the riparian zone of the Willamette River is mostly uniform with a mixed strata of herbaceous, shrub, and tree species. The mixed strata provides coverage for terrestrial and aquatic species. Trees along the Willamette River are mature and represent a thin, but functioning late-seral riparian tree canopy and provide beneficial shade to aquatic species dependent on cooler water. However, the river is wide and these functions are only effective along the shoreline. Still, the bankline is north facing so shade impacts may be greater here than on the north side of the channel. The Millrace Slough contained little canopy coverage in the southern portion of the PSA. However, several large cottonwoods located towards the confluence with the Willamette appear to provide adequate shade and temperature moderation to the northern portion of the slough. MB&G collected the percent of tree and shrub cover at riparian assessment points along the OHWM of Millrace Slough and the Willamette River. Three-quarters of these points provided greater than 50% shade coverage to create cool microclimates and aquatic habitat. Riparian assessment points collected along the Millrace Slough showed a high percentage of shade but the extensive English ivy understory could threaten the overstory in the future if left uncontrolled. Riparian assessment points collected along the Willamette River revealed several areas with adequate shade. Conversely, Himalayan blackberry infestations along the parts of the Willamette River streambank resulted in an open canopy with minimal shading capacity. Figure 6 in Appendix A shows the percentage of shade documented in the field along the Willamette River and the Millrace Slough during MB&G field efforts. 4.2Channel Stability Channel stability is partially dependent on streambank and riparian dynamics that act as the physical container of a stream and control floodplain connectivity. The majority of the riparian zones within the PSA are vegetated with a riparian forest overstory, an interspersed shrub layer, and a dense layer of herbaceous groundcover. Dense riparian vegetation and natural streambank roughness (e.g., downed wood and large boulders) attenuate streambank erosion and help to promote channel stability. The streambank of the Willamette River within the PSA has been stabilized in some areas by large concreate blocks and riprap. This riprap and concrete can promote undesirable habitat for aquatic and terrestrial species, and can reduce channel stability. However, natural substrate materials consisting mostly of cobbles, cohesive silt, and clay dominate the streambank areas and appear to promote bank stability and decrease erosion potential. The presence of erosion was recorded at each riparian data point along the Willamette River and the Millrace Slough. Eroded banks were most commonly noted within the western half of the PSA along the Willamette River and throughout the Millrace Slough. The presence of erosion within the PSA is documented in Figure 7 in Appendix A. 4.3Flood Storage Naturally vegetated riparian and floodplain areas serve a number of beneficial functions for flood storage and control. Intact vegetated riparian areas reduce the force and velocity of floodwaters by providing roughness and resistance to flood flows, which in turn, spreads flood flows more evenly over the floodplain. The combined effect page 10