KWEP Habitat Site:

Tepee Creek/IXL Road Restoration

The site is at 2965’ elevation. The surrounding watershed is forested (3000-4000’). Basal geology consists of Grande Ronde (CRB group) basalt. The hard parent materials and low to moderate relief result in a very limited bedload supply.

Cohesive soils / banks (Aquandic Haploxeralfs):

• thin (4”) A horizon = ~20% clay
• multiple Bt horizons (14”-65”) = 30 – 38% clay
• prevailing texture is clay loam

The creek is incised within its historic planform.

Fisheries Significance
Tepee Creek accounts, on average, for 6.3% of the total observed spawning in the Klickitat subbasin of ESA-listed (“threatened”) Middle Columbia River steelhead. Extensive reaches are incised and intermittent. Spawning habitat is marginal and rearing conditions are poor. The reach is located within one of the top priority areas of the Klickitat Lead Entity Strategic Salmon Recovery Strategy.

Problem
Rearing and spawning habitat for steelhead is limited, and stranding of juveniles is also an issue: the reach dried up in 4 out of 5 years preceding project implementation. Field indicators and hydraulic modeling indicate that Tepee Cr. is entrenched 3 to 4 feet within its former floodplain. Capture of a forest road ½ mile downstream is causing subsequent headward incision. Peak flows associated with upstream road densities have increased (hydrologic modeling suggests 7.3% increase for a 2.5-year storm).

• Increase flow duration / increase floodplain storage
• Enhance in-channel habitat conditions for spawning and rearing steelhead
• Restore suitability of valley bottom for medicinal and traditional food plants
  

a. Increase survival from egg to emergence (reduced fine sediment)

b. Increase key habitat quantity and habitat diversity for juvenile rearing steelhead
c. Increase perennial rearing opportunities in intermittent reaches by improving base flows.

• Ungaged
• Contributing drainage area of 8.4 sq. miles
• Peak flow hydrology is driven by rain-on-snow events
• Base flow (for years when it exists) = 10-12 gpm

Conceptual:

Import gravels to raise the bed elevation to restore overbank flow frequency to the pre-disturbance floodplain

Process:

• HEC-RAS was used to develop typical design dimensions were developed to restore overbank access at the 1.5-year flow (approximately 80 cfs)
• Design dimensions were cross-checked for with nearby analogues and regional geometry equations (Castro and Jackson 2001)
• Average slope
• 30% Drawings / Fit-in-the-field

Design Parameters:

• Longitudinal profile slope = 0.93% (0.0093 ft/ft)
• 2:1 sideslope (horizontal : vertical)
• Bankfull cross-sectional area = 19.7 ft2
• Bankfull top width = 18.4 ft
• Hydraulic radius = 1.04 (depth = 1.36 ft)

Implementation:

• A 140’ coarsened riffle (3%) was constructed at the downstream end of the reach
• Imported gravel to raise bed elevation (~3’) and reconstruct pool/riffle sequences along 1740’
• Riffles were constructed on an average slope of 0.93% with a bankfull width of 18.4’
• Ninety-five feet of new channel constructed
• Reconnected 135’ of historic channel
• Overall reach lengthened to 2090’
• 28 LWD jams constructed along channel margins to maintain pool depths, provide cover, and restrict bank erosion
• Numerous LWD placements constructed on floodplain
• Salvaged existing vegetation (sod mats and shrubs)
• Salvaged alluvial gravels (where they were present)
• Removed 2 culverts and related fill from an abandoned cross-valley road alignment
  
  Sequencing/staging
  Implemented over two field seasons:
• Construction of riffles, downstream grade control, and roughly half of the LWD jams was completed in Fall 2006
• Maximum discharge over winter 2006/2007 = 143 cfs
• Finishing work on pools and riffles, floodplain treatments, LWD jams, revegetation, and fence construction was completed during Summer 2007

Results:

Photo documentation
Pre- and post-project

Groundwater
Monitoring Wells

Habitat
Residual Pool Depths

Fisheries
Observed steelhead spawning

• 1.3’ and 2.4’ increase in average annual groundwater surface elevation
• Restored access at bankfull or lower flows to four side channels totaling 835 lineal feet
• Roughly 3100 ft2 of perennial emergent wetland was created/enhanced
• Rapid vegetative recovery, particularly in areas where salvaged plant materials were used
• Two steelhead redds observed within the reach
• juvenile O. mykiss abundance was 2x greater than pre-project
• Rapid colonization by macroinvertebrates and juvenile steelhead

Will Conley – YN Fisheries Program: Project Management - Design - Construction Oversight

Mike McAlister, PE - Interfluve, Inc.: Design - Construction Oversight

Mike Brunfelt - Interfluve, Inc.: Design - Construction Oversight

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