Transcript
Steelhead Haven Landslide Steelhead Haven Landslide Fine Sediment Reduction Fine Sediment Reduction
Project Project
Tracy Drury, PEAnchor Environmental L.L.C.
Pat StevensonStillaguamish Tribe of Indians
Stillaguamish Tribe’s InterestsStillaguamish 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
Steelhead Haven Landslide 2004Steelhead Haven Landslide 2004
Historical PerspectiveHistorical Perspective
19651965 20002000
Then came 1967…Then came 1967…
Project PlanningProject 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
Project DesignProject Design
Design conducted, 2005-06Design conducted, 2005-06
ObjectivesObjectives Maximize sediment storageMaximize sediment storage Promote long-term stabilization of the slidePromote long-term stabilization of the slide Improve in-stream habitat conditionsImprove in-stream habitat conditions
ConstraintsConstraints No increase in flood impact to the local communityNo increase in flood impact to the local community
Preliminary Design ConceptPreliminary Design Concept
Slide Failure: January 2006Slide Failure: January 2006
BackwaterBackwater at low flowat low flow
Management ConcernsManagement Concerns
Management ActionsManagement Actions
Opening a channelOpening a channel
Channel BeginningsChannel Beginnings
January 29January 29thth 2006 2006
Flow through the treesFlow through the trees
Where the river wants to goWhere the river wants to go
Channel we clearedChannel we cleared
Former Former ChannelChannelBankBank
Pre-slidePre-slideHead scarpHead scarpLocation Location
730730FeetFeet
Post Slide Post Slide ChannelChannel
Redesign ConditionsRedesign Conditions
Creek Draining the SlideCreek Draining the Slide
Creek Mixing with RiverCreek Mixing with River
Project DesignProject 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
River 2D Hydraulic Model Output - DepthRiver 2D Hydraulic Model Output - Depth
River 2D Hydraulic Model Output - VelocityRiver 2D Hydraulic Model Output - Velocity
Expected Channel MigrationExpected Channel Migration
Expected Head cutExpected Head cut
Expected ChangeExpected ChangeLog Cribwall PlacementLog Cribwall Placement
Temporary Bridge Temporary Bridge
Isolating the River From the Construction Isolating the River From the Construction
Log Cribwall 1300 feet long, 25 feet high Log Cribwall 1300 feet long, 25 feet high
Ballast Blocks Approximately Every 50 Feet Ballast Blocks Approximately Every 50 Feet
Backfilled With Woody Debris Backfilled With Woody Debris
What the River Will See What the River Will See
Approximately 20 Acre-feet of StorageApproximately 20 Acre-feet of Storage
As-BuiltAs-BuiltConditionsConditions
First Flood EventFirst Flood Event
Channel Migrated Toward the StructureChannel Migrated Toward the Structure
Migration Progressing Downstream Migration Progressing Downstream
Take Home MessagesTake 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
Steelhead Haven Landslide Steelhead Haven Landslide Fine Sediment Reduction Fine Sediment Reduction
Project Project
Tracy Drury, PEAnchor Environmental L.L.C.
Pat StevensonStillaguamish Tribe of Indians
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