Lower South Fork McKenzie River Floodplain Enhancement Project McKenzie River Ranger District Willamette National Forest

Project Location The project is located in the South Fork McKenzie River Watershed, approximately 50 mileseast of the town of Eugene, . The project area is approximately 784 acres in size and is located along the South Fork McKenzie River from the base of Cougar Dam to the confluence with the McKenzie River (approximately 4.5 miles). This area includes the mainstem channel and all current and historic side channels and floodplain. Most of the project area is under Forest Service ownership, except for approximately 32 acres owned by the US Army Corps of Engineers. The figures below provide further information about the project location. Figure 1 shows the location of the McKenzie River Ranger District. The location of the project (outlined in red) in relation to the McKenzie River sub-basin (outlined in blue) is shown in Figure 2. Figure 3 shows the project area design.Figure 5 shows the 28 wood source units. Purpose and Need The purpose of this project is to restore, to the extent practicable, the physical, chemical, and biological processes that maintain a healthy and resilient floodplain ecosystem. A well-functioning floodplain will provide diverse habitat for aquatic and terrestrial communities, including ESA- Threatened spring Chinook salmon and bull trout, Pacific lamprey and other native fishes, western pond turtle, amphibians, beaver, and waterfowl.Historically, the lower South Fork was a large alluvial valley with a complex network of side channels and frequently inundated floodplain (Figure 4). It was a depositional zone for much of the sediment, wood, and nutrients coming out of the South Fork drainage.As is typical of low gradient, alluvial valleys, this area was very biologically productive.According to 1937 surveys, the South Fork was the most important tributary for spring Chinook salmon spawning and the confluence area was known as a “bull trout paradise” that was intensively fished. Unfortunately, the South Fork has been significantly altered in the last century. Cougar Dam was built by 1963 for flood control and power generation. Associated with construction of the dam was straightening and channelization of the lower river with substantial amounts of levee, fill, and riprapmaterial.In addition, large wood was removed from the river for timber and navigation purposes. These combined activities have limited the sediment and wood supply, altered the flow regime, reduced channel complexity, and restricted off-channel and floodplain connectivity. A recent habitat survey revealed very low pool habitat (12%) and wood abundance (<10 pieces/mile). The dominant substrate in both pools and riffles is cobble – too large for spawning. Fine sediment is no longer deposited onto floodplains, limiting nesting habitat for turtles. Although Cougar Dam presents a major obstacle to floodplain restoration by altering flows and blocking wood, sediment, and nutrients, management actions can significantly improve conditions. By removing levees, fill, and riprap and adding large wood and sediment we will: Increase pools and pockets of slow water so fish can feed and rest, Provide cover from predators, Retain gravels necessary for fish spawning and fine sediment needed for lamprey rearing and western pond turtle nesting, and Maintain a well-connected floodplain with abundant side channels, ponds,and wetlands for amphibians, beaver, waterfowl, and fry and juvenile fish rearing. Recent studies indicate that stream biodiversity and productivity is greatest in streams that have a complex network of side channels (Cluer and Thorne 2013, Martens and Connolly 2014). Complex streams with a well-connected floodplain can be up to 250% more biologically productive than single thread channels (Bellmore et al. 2013). A review of projects designed to restore floodplain connectivity and side channel habitat increased salmon and trout production by 27-34% (Ogsten et al. 2014). By adding large wood to Deer Creek, we will be creating habitat features (pools, cover, gravel, side channels) that are important for native fish and wildlife. Proposed Action This project proposes the following activities (Figure 3): Approximately 54acres of levees (embankments built to prevent the overflow of a river), fill (material placed to dry out wetted areas),and riprap(material used to armor stream banks against scour and erosion) would be removed from stream banks and historic floodplainsusing heavy equipment. This material would be used to raise the elevation of the incised mainstem channel in order to restore flow to historic side channels and floodplain and to provide additional gravels and sedimentto the system. Up to 4,000 pieces of large wood would be placed in stream channels and across adjacent floodplains. This wood wouldprimarily be sourced from 28 upland units totaling 102 acres(Figure 5). There would be approximately 66 acres of gaps, primarily 2-3 acres each, and 36 acres of thinning.Some wood would come from areas of levee and fill removal. Most trees would be pushed over with heavy equipment to keep the root wad attached (which has more ecological value). Up to three ponds would be made larger and deeper with heavy equipment. They are currently shallow and ephemeral and expanding them will provide year-long benefits to Western pond turtle, waterfowl, and amphibians. Up to three culverts would be replacedand three road crossings would be removed to improve flow and aquatic organism passage. Approximately 3,100 linear feet of road would be decommissioned following access for the project All temporary roads and areas of disturbance would be fully rehabilitated and replantedwith native vegetation.

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Figure 1 and 2 - Lower South Fork McKenzie River Floodplain Enhancement Project

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Figure 3 - Lower South Fork McKenzie River Floodplain Enhancement Project Design

Lower South Fork McKenzie River Floodplain Enhancement Project 4 Figure 4 - A LiDAR Bare Earth image (with vegetation removed) revealing the historic alluvial fan and complex channel network of the lower South Fork McKenzie River.

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Figure 5. Wood source units in relation to the project area.

References Bellmore, J.R., C.V. Baxter, P. Connolly, and K.D. Martens. 2013. The floodplain food web mosaic: a study of its importance to salmon and steelhead with implications for their recovery. Ecological Applications, 23(1): 189-207. Cluer, B.L. and Thorne, C.R., 2013. A stream evolution model integrating habitat and ecosystem benefits. River Research and Applications. Martens, K.D., and P.J. Connolly. 2014. Juvenile anadromous salmonids production in Upper Columbia River side channels with different levels of hydrological connection. Transactions of the American Fisheries Society 143:757-767. Ogston, Lindsey et al. 2014. Watershed scale effectiveness of flood plain habitat restoration for juvenile coho salmon in the Chilliwack River, British Columbia. Canadian Journal of Fisheries and Aquatic Sciences, 2015, 72(4): 479-490.

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