Scott 2023 valley bottom reset monitoring Deer Creek Oregon

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Scott, D. N. (2024). Widespread wood placement and regrading drive lateral connectivity and reworking of the channel and floodplain in a valley bottom reset to Stage 0. Geomorphology, 446, 108987.

credit:https://www.sciencedirect.com/science/article/pii/S0169555X23004075?via%3Dihub

Notes[edit]

  • Documents restoration in the Deer Creek on the McKenzie River in the Willamette Basin. Project is near the "Finn Rock Project", which is in the mainstem McKenzie.
  • Project aims to increase lateral connectivity and retention of wood and sediment, and the vegetation and wood structures necessary to sustain the condition.
  • Deer Creek is very low flow system with 59km2 watershed, with common peaks over 10cms and 1/year 40cms, but base flow nearing zero (annoyingly little info on hydrology).
  • Valley bottom was regraded using a mean "geomorphic grade line" over 2.5 km of stream--gradient 2%, valley width, 60-150m
    • Phase 1 "Upstream/Downstream" 2016 - 200 logs/km and limited GGL flattening. Initial project, less intensive. Monitored
    • Phase 2 "Budwrom/Upstream" 2020- extensive GGL and 4x wood load. Monitored. enough wood that most logs were touching!
    • Phase 3 "Middle" and Phase 4 "Downstream" 2021-22 were not monitored.
  • How does floodplain wood placement in loose spatially distributed pattern, sometimes stabilized by entanglement or burial, then rearrange?
    • Phase 2 resulted in much larger scale floodplain change than experienced at Phase 1 during higher flow. Wood in Phase 2 reorganized into jams organized around existing veg or buried wood (not just key pieces as described by Abbe & Montgomery 2003.
    • Pool area measured as % of valley bottom increased from 6.6% to 8.2% and 3.2% to 4.1%
    • Evidence of floodplain alluvial work and deposition and very low river stage, and maintenance of off channel features.
    • Images suggest rapid recruitment of vegetation in floodplain/channel and increase in mosaic complexity (many small patches rather than large bars in meandering river bar system.)

Questions[edit]

  • Unknown whether multi-thread stream/wetland complex will sustain in the future, or if a large event will reestablish channel incision. No observation of substantive upstream recruitment.
  • Unknown whether a large flood event might result in mass mobilization of wood, or if a reinforcing feedback loop has established, where increased wood density has resulted in reduced wood mobility.
  • How does reestablishment of a river-wetland corridor affect invertebrate populations in the reach and fish gut content?