Current Site Conditions
The lower 1.25 miles of Deer Creek features a relatively wide floodplain in an unconfined valley. From river mile 1.25 to 2.25, Deer Creek is defined by a much more narrow and confined bedrock valley. Site receives high organic matter input (such as deciduous leaf litter), and seems to support healthy and diverse invertebrate populations. Over 60 rainbow and cutthroat salmon redds (spawning sites) were found per river mile during an ODFW survey in 2015. Because salmon seem to utilize every available gravel patch suitable for spawning, project planners believe this may be indicative that salmon populations in Deer Creek are limited mostly by quantity of spawning habitat.
Deer Creek following the 1964 flood (Source: Kate Meyer 2015)
Major flooding event, occurring in 1964, scoured the floodplain and channel of sediment and woody debris, the US Forest Service salvaged the remaining woody debris. Another flood in 1996 further reduced the roughness or complexity of the river channel, conditions which favor healthy invertebrate ecosystems and salmon spawning habitat. The removal of woody debris by the USFS likely stimulated a positive feedback loop: Removal of woody debris decreased channel complexity and sinuosity, this geomorphology focused fluvial discharge mostly into a single incised channel, which would have decreased channel to floodplain connectivity. Woody debris and sediment entering Deer Creek was much less likely to become entrenched and remain within the floodplain or in an activated channel. Decreased residency time of woody debris or sediment further reduced Deer Creek’s capacity to retain the very same woody debris and sediment. Therefore, the initial removal of woody debris by the USFS following the 1964 flood likely initiated a positive feedback loop which consistently decreased Deer Creek’s natural capacity to retain woody debris and sediment.
Restoration of the lower 2.25 river miles of Deer Creek would be the last step needed to completely restore an otherwise functional tributary system.
This project has a high potential for success, willing land owners and partners, minimal need for further maintenance and investment, and the site is easily accessible for education and outreach. Project success has a high potential to increase water storage potential of Deer Creek, a quality of the McKenzie River Watershed which will be more valuable to aquatic ecosystems and humans downstream as climate continues to warm and dry.
Project Goals: Replicate Pre-Flood Conditions
Prior to project implementation, Deer Creek contained about 100 pieces of woody debris per mile, most of which is in the small size class. Immediately upstream from the project site (upstream from river mile 2.25) featured relatively healthy and self sufficient in-stream and floodplain habitat, containing around 375 medium to large pieces of woody debris per mile. The Deer Creek Floodplain Enhancement project aims to improve water quality and restore aquatic habitat in an upstream tributary of the McKenzie River. 400 trees (200 with root-wads attached) was obtained from upland floodplain forest thinning, was placed along 1.6 miles of active channel. Additionally, 25 live stream side trees will be pulled over or dragged into the channel and floodplain. Large wood will be placed in the channel in a way which replicates conditions prior to major flooding events. Current upstream conditions were used as a reliable reference to what ideal Deer Creek conditions should be. The aim of this project is to reintroduce woody debris to the channel and slow the flow of Deer Creek. This allowed gravels and fine sediment to accumulate naturally and increase ideal spawning habitat for rainbow and cutthroat salmon, as well as foraging habitat for bull trout. Stream Stewardship 2016 preformed stream inventory on a subsection of larger Deer Creek side channels. Data gathered by our team was used for baseline and trend monitoring of the channel response to woody debris, and potential reactivation of floodplain secondary channels and pools in the lower reach of Deer Creek. The 2016 Stream Stewardship team and it’s partners conducted Floodplain Pool Surveys and Side Channel Morphology Surveys which included large woody debris count.