Phase I Summary
Phase I of the South Fork McKenzie River Floodplain Enhancement project will enhance habitat conditions within the lower mile of the river and restore connections to over 200 acres of floodplain.
- Removal of sediment on approximately 20 acres in the South Fork floodplain. Of this, approximately 5 acres of artificial levees, fill, and riprap and about 15 acres of other natural sediment deposits that will be removed and redistributed for the purpose of restoring flows paths to historic side channels and as a sediment source for aggrading the main stem channel.
- Aggradation of 1 mile of incised main stem South Fork channel.
- Placement of over 1,000 pieces of large wood and whole trees.
- Decommissioning of 0.6 miles of roads within the Project area.
Primary Response (River Processes)
- Increase sediment storage, channel migration/avulsion, and diversity/frequency of geomorphic features by 25% within 5 years of project completion.
- Increase wood abundance by at least 1000% and retain at least 90% of project wood within project reach within 5 years of project completion.
- Decrease the average annual depth of water by at least 25% in 50% of monitoring wells within 2 years.
- Increase area of floodplain inundation and secondary channel habitat during annual peak flow (approx. 4,000 cfs) and during base flow (approx. 300 cfs) by at least 50% within 2 years of project completion.
Secondary Response (Habitat Characteristics and Water Quality)
- Increase substrate size class diversity in wetted channels by 25% within 2 years of project completion.
- Increase diversity of water velocities by 25% within 2 years of project completion.
- Reduce surface water temperature during the warmest time of year at base flow by 1 degree C within 10 years of project completion.
Tertiary Response (Biological Community)
- Increase spring Chinook salmon redd abundance within the project area by 25% within 5 years of project completion.