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Physical Stream Habitat

Physical Stream Habitat. What is “Habitat”?. Broad Definition (EPA): “The spatial structure of the environment which allows species to live, reproduce, feed and move” In Relation to Streams (USGS):

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Physical Stream Habitat

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  1. Physical Stream Habitat

  2. What is “Habitat”? Broad Definition (EPA): “The spatial structure of the environment which allows species to live, reproduce, feed and move” In Relation to Streams (USGS): “The physical and chemical characteristics of a stream that determine suitability for habitation and reproduction of stream organisms”

  3. What is “Physical Habitat”? “The template of water depth, water velocity, substrate, cover and temperature that supports the stream ecosystem” – USGS

  4. Hydrologic Conditions Geology Topography Land Use Vegetation Stream Morphology Physical Habitat Interspecies Interactions Chemical Habitat Aquatic Community

  5. Measurable Characteristics of Physical Habitat • Channel morphology / type • Flow regime • Sediment texture / mobility • Bank structural features / stability • Riparian condition and connectivity • Physiochemical – temperature, DO, metals, nutrients, turbidity, etc.

  6. Mill Creek

  7. Salmon and trout habitat requirements include: • adequate but not excessive stream flows • cool well-oxygenated unpolluted water • streambed gravels that are relatively free of fine-sediments • adequate food supply • instream structural diversity (interposed pools, riffles, hiding and resting cover) Washington State Dept of Fish Wildlife

  8. Physical stream characteristics affect stream organisms by defining: • Habitat volume • Habitat quality • Disturbance magnitude • Disturbance frequency

  9. Habitat varies over spatial & temporal scales Stream Corridor Restoration, 199x

  10. Heirarchical Classification System Large Scale Fine Scale

  11. Reach Type Watershed Segment Geomorphic Unit Microhabitat Type 102 m 10-1 m 103 m 101 m 100 m How is each scale important to the species of interest?

  12. Salmon Macroinverts Temporal Variability incorporates ‘predictable’ and ‘unpredictable’ cycles

  13. Physical habitat a function of processes operating at multiple spatial and temporal scales How do we objectively assess it?

  14. Define Stream Habitat Types (Classification) • Bisson et al, 1982 • McCain et al, 1990 (USFS) • Hawkins et al, 1993 (USFS) • Thomson et al, 2001 (UK, AUS) Fish -Centric

  15. McCain et al, 1990

  16. McCain et al, 1990 Bisson et al, 1982

  17. Hawkins et al, 1993

  18. Hawkins et al, 1993

  19. McCain et al, 1990

  20. Hydraulic Habitat Flow types can be distinguished by velocity and depth using Froude Number v F = gd

  21. Panfil & Jacobson, 2000

  22. Thomson et al, 2001

  23. Stream Habitat types are created and maintained by erosion and deposition of sediments. Hjulstrom’s Diagram

  24. Mechanics of Habitat Formation • Shear Stress/Velocity Reversal Hypothesis • Helical Flow • Contraction/Expansion of Flow

  25. t = rghs v ~ f(Rs) Knighton, 1998

  26. Helical flow in meander bends Knighton, 1998

  27. Flow contraction and expansion Wohl, 1998

  28. Increased roughness reduces shear, promoting deposition of finer material McBain & Trush, 2004

  29. What promotes Habitat Diversity? Diversity is a function of fluctuations in erosion and deposition processes over varying scales Disturbance

  30. Natural stream systems are subject to the full spectrum of spatial & temporal disturbances • Natural flow regime • Varying sediment inputs • Structural diversity - LWD Episodic Sediment Transport

  31. Natural Flow Regime • 5 characteristics: • Frequency • Magnitude • Duration • Timing • Rate of Change • Key factor = extremes included

  32. Disturbance acts to ‘reset’ processes Mount, 1995

  33. Large Woody Debris • Increases local scour and deposition • Provides structural habitat • Transient nature (moves, breaks, clumps, decays) All add to habitat diversity and complexity

  34. Plane Bed Wood-poor Pool-riffle Buffington & Montgomery 1999

  35. Wood-rich Pool-riffle Buffington & Montgomery 1999

  36. Stream habitat diversity maintained over time Species adapt • Salmon – spawning and run timing • Foothill Yellow-legged Frog – oviposition timing • Cottonwood regeneration – accidental forest

  37. Diversity in Trout Habitat Redrawn by Bledsoe from Schlosser (1995)

  38. Alterations to flow regime & sediment supply alter habitat diversity & biodiversity Stream Corridor Restoration, 1998

  39. Alterations to Stream Systems • Flow extraction • diversions • groundwater withdrawal • Flow augmentation • ag runoff • hydropower • Sedimentation • development • logging • mining • Sediment Loss • dams • mining

  40. Degradation Aggradation • Channel Bed Coarsening • Loss of Fines/Gravels • Vegetation Encroachment • Low bed mobility • Channel Bed Fining • Excess Fines/Gravels • Lack of vegetation • High bed mobility

  41. Block Sediment “Flatline” Hydrograph Disrupt Connectivity Channel Degradation – bed coarsening, loss of fines/gravels Loss of extreme flows (loss of disturbance) – low bed mobility, vegetation encroachment, low habitat diversity Block habitat access, alter water chemistry, shift from lentic to lotic system Effect of Dams

  42. What can we do to improve spawning habitat conditions downstream of dams?

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