Introduction to Nature-like Fishways for Dams
Recorded on April 11, 2017 (120 minutes)

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Dam-related problems include blockage of fish migrations, drowning hazards, failure hazards, reservoir sedimentation, habitat loss, and tailwater erosion.  Some environmental problems can only be addressed through dam removal while other issues, where removal is not a viable option, can be remediated by dam modification and nature-like fish passage. Traditional fish passage projects have typically focused solely on passage of single or few large game species.   As the name implies, nature-like fishways emulate natural river geometry.  Nature-like fish passage includes full width dam modifications that have been applied to address dam and levee stability issues, eliminate dangerous hydraulic undertows, provide spawning habitat, provide recreational boating, grade control or sediment stabilization in dam removal and river restoration, and pass the full spectrum of native fish species.  These broad benefits have drawn a diversity of funding from federal, state, and local sources.  This course will introduce nature-like fishway types, design principles, applications, case examples, and associated benefits

Key Takeaways:

  • An increased understanding of dam-related effects on physical and ecological processes, safety, and other environmental issues
  • Underlying hydraulic, geomorphic, and biological considerations in addressing dam-related problems
  • An introduction to nature-like fishway types and applications
  • Elements of fishway funding, design, and construction
  • Case examples and evaluation of benefits

Dr. Luther Aadland is a river scientist for the Minnesota Department of Natural Resources and has worked as a river restoration consultant across the United States.  He received a B.A. degree in Biology from Concordia College-Moorhead in 1979, a M.S. in Zoology from North Dakota State University in 1982 where he designed, built, and studied artificial reefs, and a Ph.D. in Biology from the University of North Dakota in 1987 where he designed experimental streams based on natural channel morphology, and studied chinook salmon interactions with native species in a large reservoir.  He subsequently received additional training in fluvial geomorphology and hydraulic modeling.  He has worked for the Minnesota Department of Natural Resources as a river scientist for 29 years.  His research and publications include topics in fluvial geomorphology, habitat requirements of fish and mussels, relationships between hydrology and aquatic microhabitat, stream ecology, river restoration, dam removal, nature-like fish passage, and other river sciences.  He has taught workshops in these fields through the Minnesota DNR, University of Wisconsin and other agencies for 22 years.  His book, “Reconnecting Rivers” provides design rationale and case examples for dam removal, river restoration, and nature-like fish passage.

Luther has designed more than 180 river restoration projects in collaboration with engineers and scientists from federal, state, and local units of government.  These projects have included restoration of channelized rivers, river restoration in sediment-laden reservoirs following dam removal, artificial reefs, experimental research streams, restoration of critical habitat, ecologically sound flood damage reduction, and nature-like fish passage.  He developed the rock arch rapids concept to address dam-related drowning hazards, fish passage, and tailwater erosion problems associated with low-head dams.  Hydraulic undertows at some of these dams had caused numerous drowning deaths.  With elimination of the “drowning machine” hazards, safety at these dams has been substantially improved despite increased recreational use.  Project benefits have included improved public safety, restoration of ecological functions and biodiversity, and establishment of self-sustaining features that do not require operations or routine maintenance.

  1. Introduction
  2. Pertinent Dam-Related Problems and Issues
    1. Migration barriers of fish and other aquatic life and the broad ecological implications
    2. Dam instability and failure potential
    3. Tailwater erosion
    4. Hydraulic undertows and public safety
    5. Inundation of critical habitats
    6. Reservoir sedimentation
    7. Others
  3. Evaluating Solutions and Alternatives
    1. Site constraints, problems addressed, advantages and limitations of alternatives
    2. Dam removal
    3. Nature-like fish passage
      1. Why nature-like?
      2. Types and applications
        1. By-pass fishways
        2. Rock ramps- the Rock Arch Rapids
        3. Hybrids
  4. Design Considerations in Nature-like Fish Passage
    1. Stability issues
    2. Hydraulics and bed materials
    3. Fish hydrodynamics
    4. Habitat provided by fishway
  5. Case Examples and Indicators of Success
  6. Conclusions