Design Tips for FishPassable Culverts

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Design Tips for Fish-Passable Culverts
Joel Cahoon and Matt Blank Montana State
University
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Information and Data for Fish Passage

• Still a very good overview
• Tillinger, T. N. and O. R. Stein. 1996. Fish
  passage through culverts in Montana a
  preliminary investigation. FHWA/MT-96/8117-2.
  Available at
• http//www.mdt.state.mt.us/research/docs/research_
  proj/final_report_fishculverts.pdf
• Still a pretty good bibliography
• The FishXing site has a downloadable bibliography
  with references and abstracts
• http//www.stream.fs.fed.us/fishxing/

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Factors Influencing Fish Passage
In high-gradient mountain streams

• High water velocity
• culvert length
• fish swimming capability
• Shallow water depth
• Outlet drop
• outlet pool depth

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Water Velocity and Culvert Length
References Katopodis, C. and R. Gervais. 1991.
Ichthyomechanics. Working document. Freshwater
Institute, Central and Arctic Region, Department
of Fisheries and Oceans. 501 University
Crescent, Winnipeg, Manitoba, Canada. R3T
2N6. Katopodis, C. 1994. Analysis of
ichthyomechanical data for fish passage or
exclusion system design. Proceedings,
International Fish Physiology Symposium.
Vancouver, Canada, July 1994. American Fisheries
Society and Fish Physiology Association. pp.
318-323.
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Factors Influencing Fish Passage

• Shallow water depth

Many fish in the Seeley study were observed to
navigate depths as shallow as 2.5 inches
(juveniles) or 3.5 inches (adults).
no less than this
General rule depth no less than the height of
the design fish.
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Factors Influencing Fish Passage

• Outlet drop
• outlet pool depth

Avoid outlet drops! When assessing an existing
culvert, be aware that pool depth and outlet
drop/flow depth are also factors in passage
success.
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Flowchart Based Screens
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FishXing
http//www.stream.fs.fed.us/fishxing/
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HEC-RAS
http//www.hec.usace.army.mil/software/hec-ras/hec
ras-download.html
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HEC-RAS
Some thoughts A better hydraulic model than
FishXing, mostly because of the ability to link
the culvert with a more real depiction of the
stream. Allows multiple culvert barrels and very
complex geometries.
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HEC-RAS
More thoughts Uses the FHWA culvert model, which
is still only inlet/outlet based, unless you
construct the culvert using cross section
geometry and do not expect it to be more than
half full (no cut banks allowed).
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Natural Substrate or Not?
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Still the Best Culvert Reference
Bodhaine, G. L. 1968. Measurement of peak
discharge at culverts by indirect methods. In
Techniques of Water Resources Investigations of
the United States Geological Survey. Book 3,
Chapter A3. USGS. MSU Renne Library Call
Number I 19.15/5bk3/chapA3
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A Look Back at Stein and Tillingers
Recommendations (pp 27-28)

• weakest fish
• consistent channel slope
• straight reach
• minimize culvert length
• culvert at stream grade or flatter
• natural substrate in culvert
• corrugated culverts better
• roughen the wall of a smooth culvert
• bridge?

• 10. multiple barrels
• culvert velocities similar stream
• free surface, subcritical, outlet control
• resting pools at inlet and outlet
• avoid concrete aprons
• increase tail water depth
• minimum depth equals fish height
• baffles?

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Questions?