1. US Army Corps of Engineers Detroit District Knife River Reducing Sediment Delivery Through Forest Restoration

2. US Army Corps of Engineers Detroit District Drainage Area = 88 mi 2 Mostly forested Close to Duluth Only naturalized wild steelhead population in MN Only MN trib to Great Lakes w/o fish migration barrier

3. US Army Corps of Engineers Detroit District Knife River Background Federal Harbor Knife River is a significant source of sediment to the lake and harbor and has use impairments due to sediment. As such, a TMDL has been established.

4. US Army Corps of Engineers Detroit District Knife River Source of Sediment Mass Wasting

5. US Army Corps of Engineers Detroit District Knife River The Problem The Knife River watershed was historically composed of old-growth red and white pines with some hardwoods. Modern logging activities have replaced those species with a mono-culture of aspen. Local scientists believe that this shift is species has altered the hydrologic response of the watershed resulting in increased flashiness and increased erosion. Local stakeholders are interested in initiating a forest restoration program but would like the following questions answered first: 1.How large of a reduction in sediment delivery is expected if the forest is restored to pre-European settlement species? 2.Are some sub-watersheds more sensitive to restoration than others? 3.What role does the beaver play in storing sediment and reducing flashiness?

6. US Army Corps of Engineers Detroit District Knife River Summary Watershed response to forest restoration modeled with HSPF Impact of beaver dams on sediment supplies modeled with RAS Hydrologic sensitivity index developed Historic flows statistically analyzed

7. US Army Corps of Engineers Detroit District First Date with Knife River Temperature and Precipitation

8. US Army Corps of Engineers Detroit District Clay-Rich TillAverage Slope = 0.8 % Knife River Soils and Topography

9. US Army Corps of Engineers Detroit District Knife River Land Cover and Forest Canopy

10. US Army Corps of Engineers Detroit District Knife River Watershed Model - HSPF Tree Age Effect Hydrologic response following clearing and subsequent planting of a pine forest at different recovery ages 0 years 2 years 5 years 10 years 20 years 50 years 100 years Forest Restoration Re-establishment of mature coniferous forest representative of pre-European settlement 0% 25% 50% 75% 100%

11. US Army Corps of Engineers Detroit District Knife River Watershed Model - HSPF Calibrated to Flow at d/s gage

12. US Army Corps of Engineers Detroit District Knife River Watershed Model – Extent of Forest Restoration

13. US Army Corps of Engineers Detroit District Knife River Watershed Model – Extent of Forest Restoration

14. US Army Corps of Engineers Detroit District Knife River Watershed Model – Tree Age

15. US Army Corps of Engineers Detroit District Knife River Watershed Model – Tree Age

16. US Army Corps of Engineers Detroit District Knife River Beaver Influence on Sediment Castor canadensis is the largest rodent in North America, growing to 60 lbs over an average life span of 24 years. Beaver dams can significantly affect stream flashiness Beaver dams can store a large quantity of sediment A large pulse of sediment can be mobilized upon breaching

17. US Army Corps of Engineers Detroit District Intern canadensis Castor canadensis Knife River Beaver Confusion

18. US Army Corps of Engineers Detroit District Knife River Beaver Influence on Sediment

19. US Army Corps of Engineers Detroit District Knife River Summary of flow at USGS Gage

20. US Army Corps of Engineers Detroit District Knife River Flashiness Index No Trend

21. US Army Corps of Engineers Detroit District Knife River Flashiness Index

22. US Army Corps of Engineers Detroit District Knife River Flashiness Index

23. US Army Corps of Engineers Detroit District Hydrologic Sensitivity Index Ranks hydrologic sensitivity of sub-basins based on slope, distance to outlet and percent disturbed land

24. US Army Corps of Engineers Detroit District Knife River Conclusions Forest restoration to Pre-European species will have a minimal effect on altering stream flows except in a few sub-watersheds Beaver dams will store water and reduce the flashiness of the stream at low flows, but have no effect once the 2-yr flow is exceeded Beaver dams only temporarily impound sediment. Larger waves of sediment are likely released when a dam or multiple dams fail

25. Questions? Contact: Dr. Jim Selegean, P.E., P.H. U.S. Army Corps of Engineers, Detroit District Great Lakes Hydraulics and Hydrology Office 477 Michigan Ave Detroit, MI 48226 313.226.6791 james.p.selegean@usace.army.mil US Army Corps of Engineers Detroit District

26. US Army Corps of Engineers Detroit District

27. US Army Corps of Engineers Detroit District Figure 39: Impacts of different beaver dam densities with unsteady flow modeling. a) far downstream cross- section b) downstream cross-setion c) cross-section immedietly downstream of dams d) within beaver dam section e) upstream of beaver dams - The black dashed line indicates time of first dam breach

28. US Army Corps of Engineers Detroit District

29. US Army Corps of Engineers Detroit District