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Biological Objectives Tied to Physical Processes. Dr. William Trush Scott McBain Arcata, CA. Outline. Geomorphic-Hydrology work with Biologist Geomorphic-Biotic linkages Attributes of alluvial river integrity Analytical techniques which include:

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biological objectives tied to physical processes

Biological Objectives Tied to Physical Processes

Dr. William Trush

Scott McBain

Arcata, CA

  • Geomorphic-Hydrology work with Biologist
  • Geomorphic-Biotic linkages
  • Attributes of alluvial river integrity
  • Analytical techniques which include:

Hydrograph component analysis, bar morphology, integration

  • Reconsideration of standard techniques on assessing impacts of dams
historical perspective
Historical Perspective
  • Need to have a good understanding of how the system historically functioned, both physical components and biotic components
        • Evaporation
        • Precipitation
        • Different Species
        • Variety of hydrologic regimen
        • Variable geology
conceptual framework
Conceptual Framework
  • For all take note of: Human land use and flow regulation, natural disturbance
bottom up vs top down
Bottom-Up vs. Top-Down
  • Bottom-Up- Biologist
    • Start under water, without understanding the history and geomorphic processes. They never challenge the base line of the river.
  • Top-Down- Geologist
    • Start above water need to consider a biological stand point.
  • Have to approach both ways- integration is the key
processes you need to go through
Processes You Need To Go Through…
  • Data
  • Spend time getting historical condition, land and species
  • Conceptual model
  • Objectives
priority hypothesis
Priority Hypothesis
  • Geomorphic
    • Dam has eliminated upstream sediment supply, decreasing in-channel coarse sediment storage
  • Salmonid
    • Spawning gravel supply has been decreased
    • Spawning habitat is limiting salmonid production
attributes of alluvial rivers
Attributes of Alluvial Rivers
  • Historical Model of “Trinity River”
    • Look at conceptual models to identify key process and formation that maintained the ecosystem
    • The process of developing the attributes is most important and different for every river
attributes of alluvial rivers cont
Attributes of Alluvial Rivers cont.
  • Spatially complex channel morphology (migrate, meander, side channels)
  • Flows and water quality are predictably variable (Trends in river that are consistent per year during certain times)
  • Bed moves frequently (1-2 year)
  • Bed scour and fill (5-10 year)
  • Balance fine and coarse sediment
  • Channel migrates/avulsion
attributes of alluvial rivers cont1
Attributes of Alluvial Rivers cont.
  • Floodplains (oxbows, fine sediment dep.)
  • Channel Resettling floods (20-50 yrs. Large scale geomorphic change)
  • Plant communities
  • Fluctuating ground water table (wetlands and animals)
channel complexity
Channel Complexity
  • Very Complex
  • Point bars (plants), scours, oxbows, sheer zones/pools (fish), side channels, variable particle size
create and maintain channel morphology
Create and Maintain Channel Morphology
  • Hydrograph
    • Print our every hydrograph for the periods of record, develop hypothesis
    • Conduct water year analysis to evaluate inter-annual flow variability (wet year vs. dry year)
    • Intra-annual flow variability with in water year, evaluate changes relate geomorphic processes and life history of key biota
    • Link biota to hydrology
other biological hotspots
Other Biological Hotspots
  • Sediment deposition
  • Channel complexity (bars, side channels)
  • Riparian vegetation
  • Spawning areas
  • Amphibian egg laying locations
  • Large wood accumulation
  • Historical perspective to understand how the system naturally worked
  • Hypotheses on how project changes the components of the system (Geomorphic-Biotic)
  • Use top/down and bottom/up approach with lots of coordination between physical scientist and biologist
  • No river is the same, nor does every dam have the same impacts
case study 1
Case Study 1
  • Overview of hydrology, geomorphology, and channel morphology of the Clavey River
  • Develop hypotheses
  • Illustrate some conceptual models and analytical tools useful for access dam-related impacts to steep bedrock rivers
summary of changes
Summary of Changes
  • Substantial loss of flow volume
  • Substantial reduction on flood magnitude and frequency
  • Constant year found base flows
  • Loss of coarse sediment supply
  • Reduction or loss of fine sediment
  • Downstream tributaries and valley walls still contribute fine and coarse sediment to channel
potential impacts
Potential Impacts
  • Accumulation of fine sediment and gravels in channel
  • Riparian and upland vegetation intrusion
  • Abandoned side channels and ponded areas
  • Reduction of residual pool volume by gravel-boulder filling
  • And…
potential impacts1
Potential Impacts
  • Reduced magnitude, duration, and frequency of bed mobility of alluvial features
  • Reduced coarse sediment storage immediately downstream of the dam