1. Steelhead Haven Landslide
Fine Sediment Reduction
Project
Tracy Drury, PE
Anchor Environmental L.L.C.
Pat Stevenson
Stillaguamish Tribe of Indians

2. Stillaguamish Tribe’s Interests

Chinook Populations at 8%
of historic levels

Fine sediments inputs was
determined to be a major
contributing factor

Success would improve
habitat conditions for more
than 30 miles downstream

3. Steelhead Haven Landslide 2004

4. Historical Perspective
1965
2000

5. Then came 1967…

6. Project Planning

Prioritized in the Chinook recovery plans, 1990, 2000,
2005

Began community involvement / public outreach, 1995

Evaluated in the Corps Ecosystem Restoration Plan,
2000

Conceptual Designs Developed, 2001

Funding for design and construction: Salmon Recovery
Funding Board (500K) and Centennial Clean Water
(500K), 2005

7. Project Design

Design conducted, 2005-06

Objectives




Maximize sediment storage
Promote long-term stabilization of the slide
Improve in-stream habitat conditions
Constraints

No increase in flood impact to the local community

8. Preliminary Design Concept

9. Slide Failure: January 2006

10. Backwater at low flow

11. Management Concerns

12. Management Actions

13. Opening a channel

14. Channel Beginnings

15. January 29th 2006
Channel we cleared
Flow through the trees
Where the river wants to go

16. Pre-slide
Head scarp
Location
Post Slide
Channel
Former
Channel
Bank
730
Feet

17. Redesign Conditions

18. Creek Draining the Slide

19. Creek Mixing with River

20. Project Design

Design conducted, 2005-06

Objectives




Maximize sediment storage
Promote long-term stabilization of the slide
Improve in-stream habitat conditions
Constraints

No increase in flood impact to the local community

21. River 2D Hydraulic Model Output - Depth

22. River 2D Hydraulic Model Output - Velocity

23. Expected Change
Log Cribwall Placement
Expected Channel Migration
Expected Head cut

24. Temporary Bridge

25. Isolating the River From the Construction

26. Log Cribwall 1300 feet long, 25 feet high

27. Ballast Blocks Approximately Every 50 Feet

28. Backfilled With Woody Debris

29. What the River Will See

30. Approximately 20 Acre-feet of Storage

31. As-Built
Conditions

32. First Flood Event

33. Channel Migrated Toward the Structure

34. Migration Progressing Downstream

35. Take Home Messages

Landslide failure forced redesign to be more highly
engineered placement

Constructability was a major decision making factor

The structure was designed to deform and settle as the
river undercuts it’s face

Thorough analysis and communications prior to the
failure facilitated permit acquisition after the failure

36. Steelhead Haven Landslide
Fine Sediment Reduction
Project
Tracy Drury, PE
Anchor Environmental L.L.C.
Pat Stevenson
Stillaguamish Tribe of Indians