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Mixing engineering and biology

Where Fish Passage is required

Connectivity is required across the landscape wherever there are fish. Fish and fish habitat assessments standards are under development for TRANS. These are will indicate species specific and crossing specific information so sensitive sites (such as spawning sites) can be avoided when planning the location of watercourse crossing sites.

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Even areas that don’t exactly look like spawning habitat ….

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…require fish passage.

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In terms of culverts, dependent on one’s viewpoint, a culvert providing fish passage is envisioned as either this:

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or this………..

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Fish Passage Criteria

• Culvert Diameter• Culvert Slope• Roughness• Velocity• In certain cases, type of fish species

and invertebrate species

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In the past, TRANS had approached regulatory agencies in comparing velocities and depths in a stream to what was in the culvert.• For example, we used to produce

this type of table:

• Note: This has now been updated.

Channel Culvert

Discharge (cms)

Stream Depth (m or Y)

Mean Stream Velocity

(m/s or V)

Inlet Outlet

Depth (m)

Mean Velocity

(m/s)

Depth (m)

Mean Velocity

(m/s) 2.3 0.5 0.8 0.5 0.67 0.5 0.49 4.5 0.75 1.0 .75 0.97 .75 0.76 7.4 1.0 1.2 1.0 1.26 1.0 1.04

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Unfortunately, we didn’t realize that the relationship between hydrotechnical design parameters was not clear to folks that weren’t used to dealing with it. For example, how did flow relate to velocity?

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???

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In order to create this basic understanding with everyone we’ve used a real life example to illustrate

the process.In this we are using the new (draft)

Fish Passage Design Discharge (FPDD).

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The project involves 12 watercourse crossings – 3 of which are fish bearing. The fish species that is present is Athabasca Rainbow Trout.

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Athabasca Rainbow Trout sampled along Highway 32

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This is fish habitat.

So is this.

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This is one of the culvert crossings we will be replacing.

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We’ve approached the issue of fish passage by using a series of

informational tools. It proves due diligence and we now have a record

of the site.Here are some of the tools.

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We produced individual site analyses using satellite imagery.

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• Topographic

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Basin Size

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• Slope

Crossing 2

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Site 2 – Slope Summary

• Channel Slope At Crossing S~ 1.2%• Upstream of Crossing S~ 2.9 to 6.2%• Downstream of Crossing S~ 1.8%• (entering receiving channel)

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In comparison Site 3 Topographic

Basin

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Slope

Crossing 3

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Site 3 – Slope Summary

• Channel Slope At Crossing S~ 1.1%• Upstream of Crossing S~ 3.2 to

8.0%• Downstream of Crossing S~ 0.8%(entering receiving channel)

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Summary Table

Inlet Outlet9540 (2) 22 28 2.0 1.2 1.35 0.39 1.1 1.1 1.1

Y @ QFPDD

(m)

VelocityFPDD

Culvert (m/s)

QFPDD

(m3/s) *

Channel (m/s)

Site DA (km2)

QDesign

(m3/s)

Y @ QD

(m)

Stream Slope at Site (%)

Design flow and corresponding flow depths calculated as per AT's Hydrotechnical Design Guidelines.* Based on AT's discussion of the recommended fish passage design discharge

Definitions:DA = Gross Drainage Area (km2)Q Design= flow (cubic meters per second)Y@ QD= depth at design flowQDesign = flow (cubic meters per second)

Y @ QD = average channel flow depth at design flow (discharge)

QFPDD = flow at fish passage design discharge

Y @ QFPDD = depth at fish passage design discharge

Velocity FPDD = velocity at fish passage design discharge

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 Definitions:  • Q - Discharge = the rate of flow of

water. It is the volume of water passing through a cross section of a channel in a given period of time. This is not a constant value; it is constantly changing. It is expressed as cubic meters per second (CMS)

• A - Area = Cross sectional area of flow in the channel.

• V - Velocity = the mean velocity for the cross section, as determined by V=Q/A.

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Definitions:  • Y - depth of flow• B – channel bed width• h – hydraulic bank height • T – top width• S – channel slope• n – roughness parameter

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Figure 1. Typical Channel Parameters: B=2.5, h=1.0, T=5.0, S= 1. 2%, n=0.06

Design flow parameters: Fish passage design flow parameters: QD = 28 m3/s QFPDD = 1.35 m3 YD = 1.5 m, YFPDD = 0.39 VD = 2.6 m/s VFPDD = 1.1/1.1 (Inlet/Outlet) Cross-sectional area for QD = AD = 6 m2 Cross-sectional area for QFPDD = AFPDD = 2 m2

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• Although implicit in this presentation TRANS embeds culverts to D/4 up to 1 meter

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Techniques we are using to enable fish passage in steeper creeks 1% and greater.

Substrate Holders

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In culverts located on higher gradient streams and those where culvert velocities at the FPDD exceed those in the natural channel, substrate holders can help to provide more low velocity zones. 

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Substrate holders are small weirs installed in the culvert to retain substrate in the culvert. The substrate provides additional roughness to reduce velocities, with an added benefit of flow variation. This method is typically effective for long culverts where backwater effects are lost.

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• Substrate holders are designed to hold an engineered streambed in the culvert while allowing for natural sediment transport processes to occur in the stream.

• for culverts ≤ 3 m in diameter, 200 mm high weirs should be used with Class 1M rock riprap, and

• for culverts > 3 m in diameter, 300 mm high weirs should be installed with Class1 rock riprap.

•  

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• The maximum spacing of the substrate holders is equivalent to the substrate holder height divided by the slope of the culvert.  

• Currently the effect of these substrate holders is being researched.

• More information is available in the draft ‘Culverts and Fish Passage’.