Fish Barrier Design Evolution in Montana 1 George Austiguy PE, Pioneer Technical Services With Contributions by Dale White PE, USFS.

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Fish Barrier Design Evolution in Montana

George Austiguy PE, Pioneer Technical ServicesWith Contributions by Dale White PE, USFS

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• Early barrier designs were based on the concept of a height barrier.• So… How high can a fish jump? Let’s try 4 ft.

• Limited data on how high a salmonid could jump => Barrier designs became based on theoretical leap estimates as a function of fish burst speed.

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How fast can a fish swim? => Data old, based on laboratory measurements, not representative of field conditions = uncertainty

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• This height based design approach led to fish barrier designs with an downstream apron on-grade with a weir crest 4 – 5 ft above the downstream design flow (typically Q50 in MT.) water surface elevation

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• Breeching of height based designed fish barrier structures for which conservative, theoretical fish leaping calculations predicted were not breachable (i.e. the fish could not leap over) led to a focus on the downstream conditions. i.e. what’s wrong with our model?

• Analysis of the breached structures indicate downstream aprons had variable hydraulic conditions which potentially fish were able to exploit and use to breach the barrier.

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Temporary Apron On-Grade Fish Barrier Cherry Creek, MT Breached by Rainbow Trout. Weir Height = 4.5 ft.


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• These variable hydraulic conditions can include clinging nappes, eddys and standing waves, and micro low-energy streams associated with turbulent flow caused by non-uniform downstream geometry;

• The ability of salmonids to exploit small variations in energy within the flow stream to pass obstructions is supported by research using PIT tagged fish and 3-dimensional modeling (M.Blank, 2005“Studies of Fish Passage Through Culverts in Montana”);

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• Research on brook trout (Kondratieff and Myrick, 2006, “How High Can Brook Trout Jump”)indicates that leaping ability by brook trout is a direct function of the water depth in the downstream region of the barrier;

• Tools available to design practitioners are typically limited to simple, 1-dimensional hydraulic models (HEC-RAS);

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Fish Barrier Design Evolution in Montana• Collectively these observations and research results pushed our fish

barrier design concepts to focus on producing downstream hydraulically uniform, 1-dimensional flow conditions, with shallow depth and high velocities to eliminate the ability of fish to leap in the first place;

• If the flow depth is too shallow for a fish to orientate to a leaping angle, it cannot jump;

• Apron flow that is supercritical (shallow and fast) uniform flow, requires a fish to constantly be in burst mode, eliminates locations where a fish could rest or leap from.

• Wing walls adjacent to the downstream apron:– Provide geometry that produces uniform flow conditions;– Produces 1-dimensional dominated uniform flow conditions=> allows 1- dimensional

hydraulic modeling better predictive performance

• Elevated apron crest maintains supercritical apron flow;• This design concept is consistent with fish barrier design guidelines

adopted by NOAA Fisheries (BOR, 2006, Fish Protection at Water Diversions)

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The specific structure design criteria used : •

– The downstream crest of the apron will be elevated 1 ft above the maximum design tailwater elevation;

• – The minimum apron length will be 16 feet;

• – The minimum apron slope will be 16H:1V;

• – The minimum weir height of the barrier will be 3.5 ft above the apron height;

and•

– The structure shall be designed to exclude fish passage up to the 50-year flow and to structurally withstand the 100-year flow.

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Hydraulic Modeling Example of Elevated ApronCourtesy of Dale White USFS


Hydraulic Modeling Example of On-Grade ApronCourtesy of Dale White USFS

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• Recent examples of this design concept are shown on the following slides

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Temporary Fish Barrier, Casias Creek New Mexico

16Smith Creek Fish Barrier Montana


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Cherry Creek Fish Barrier, Montana

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Greenhorn Creek Fish Barrier, Montana

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Muskrat Creek Fish Barrier, MontanaCourtesy of Dale White USFS

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NF Highwood Creek Fish Barrier, Montana