Graduate Thesis Or Dissertation
 

A Novel Approach to Process-based River Restoration in Oregon : Practitioners’ Perspectives, and Effects on In-stream Wood

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/n009w7099

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  • The widespread fragmentation, channelization, and simplification of river ecosystems has had acute environmental impacts, including degradation of water quality and habitat and biodiversity loss (Vörösmarty et al., 2010). These concerns have incited an increased focus on reestablishing ecological and hydrogeomorphological functions and improving habitat that has been lost in riverine ecosystems. The broad set of activities aimed at improving the environmental health of rivers, referred to collectively as river restoration, has become a multi-billion dollar industry (Bernhardt et al., 2005), and one of the most active areas of applied, contemporary water resources research (Wohl, Lane, & Wilcox, 2015). An innovative approach to process-based river restoration has recently emerged in Oregon, and is being implemented across the state by a small group of U.S. Forest Service (USFS) fisheries biologists and hydrologists. The development and dissemination of this practice – termed Stage 0 restoration – may mark an important shift in the approach to river restoration in the Pacific Northwest, yet the phenomenon remains undocumented in the literature. This research presents Stage 0 practitioners’ perspectives and a case study of the impacts of this restoration on large in-stream wood. Qualitative semi-structured interviews and participant observations were conducted with seven USFS fisheries biologists and hydrologists to characterize what inhibits and enables the implementation of Stage 0 restoration. Interviewees cited stakeholders’ fears about fish, sedimentation, and an unfamiliar morphology as serious challenges; they also noted that scientists have been crucial enablers by “bridging the gap” through advocacy and participation in stakeholder meetings. The most salient catalyst for the Stage 0 practice, however, is the interviewees’ commitment to building relationships through peer-review, mentorship and outreach. The findings from this study point to the importance of Stage 0 stakeholders engaging in transparent dialogues about values, and exploring perspectives of other groups to identify opportunities for building stronger collaborations. Continued monitoring to assess the impact of Stage 0 restoration on biophysical processes is also critical. Given the broad effects of in-stream wood on important riverine processes, a case study on this important ecosystem constituent was conducted on Deer Creek in the Western Cascades of Oregon. This research explores the effects of the experimental placement of unknown quantities of large in-stream wood in the floodplain, and the response of that wood to one year of flows after restoration. The abundance, size and spatial distribution of large in-stream wood were estimated from repeat unmanned aerial vehicle (UAV)-captured, high resolution aerial imagery of a 500-m transect of Deer Creek before (April 2016), after (September 2016), and one year following completion (September 2017). Data were compared with a 2002 field inventory from a 500-m transect of Lookout Creek in the H.J. Andrews Experimental Forest (HJA). The abundance of wood in Deer Creek more than tripled as a result of the restoration activities (from 428 to 1,560 pieces), but decreased by 25% over the year following restoration. Most of this change involved wood in small size classes (<30 cm diameter, <10 m length), which apparently was rearranged by 2016-17 winter peak flows (~1.5-year recurrence interval). The restoration efforts sharply increased wood of a particular larger size class (>60 cm diameter, 10 to 20 m length), though after restoration, Deer Creek only had about 40% as many large diameter class (>60 cm) pieces per unit stream channel length as Lookout Creek. More wood was contained in accumulations in Lookout Creek, and the accumulations were larger and more widely spaced, due to fluvial rearrangement during high flow events. Uncertainty in wood diameter and length and location of logs in repeat drone-based imagery was high. Thus, if wood monitoring using drone-mounted cameras continues in Deer Creek, it should include field verifications of sizes and establishment of a ground control network. The response seen at Deer Creek points to the importance of promoting long-term wood recruitment processes at Deer Creek, and continuing to study the stability of wood. There are opportunities for research partnerships between Stage 0 practitioners and HJA scientists, who have collectively conducted decades of research on large in-stream wood.
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