Understanding the Impacts of Culvert Performance on Stream Health

Kristin ThomasAquatic Ecologist

Michigan Trout UnlimitedTransportation and the Environment Conference

12/5/2018

Importance of adequately sized crossings

• Fish and organism passage• Stream morphology• Design considerations• Funding and partnership opportunities

Why is connectivity important?• Biologically

• Block passage of organisms• Fish• Invertebrates• Amphibians• Terrestrial

• Geomorphically • Disrupts normal stream function

• Inhibits transport• Sediment• Wood

• Changes channel shape – changes function

Culvert Problems• Inlet or outlet drop (perch)• Physical barriers• Wood debris accumulation• Excessive velocities• Insufficient water depth• Flow contraction (turbulence)• Absence of bank edge areas• Discontinuity of channel substrate• Behavioral barriers• Riparian fragmentations

How do culverts block AOP?

Perched

Velocity

Velocity/turbulence

Swimming speed

• Burst Speed• Highest speeds attainable • Maintained only for short time <20 seconds

• Prolonged Speed• Speeds fish can maintain for 20 seconds to

200 minutes• Spans speeds between burst and sustained• Often the speed used in culvert design

• Sustained• Speeds fish can maintain for long periods of

time >200 minutes

Why do aquatic organisms need to move?

• Spawning habitat• Nursery habitat• Foraging areas• Deep water refuge• Seasonal habitats• Genetic variability

Dennis Kirkland

Seasonal Movement

• Life stage movement needs• Movement to meet a variety of

needs• Reproduction• Colonization of available habitat• Chemical or thermal refuge• Food

• Can be daily, weekly, seasonally, yearly, or less

Migration Timing

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umbe

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Design Window

Gullett, Kale. Aquatic Organism Passage. NRCS-ENTSC

Genetic Variability

• Genetic diversity correlated to population’s ability to adapt• Genetic diversity foundation of ecosystem diversity• Sustainability of a population depends on the maintenance of genetic

diversity• Genetic drift and inbreeding depression

• Cannot maintain genetic diversity in small populations• Must be able to move and interbreed with other populations

Not just fish!

Inter-specific Interactions

• Occurrence of some species depends on presence of others

• Freshwater Mussels• Many species depend on fish hosts to

complete lifecycle• Larval mussels, glochidia, attach to fish gills

to complete lifecycle• Many will attach to any available fish• Some are fish species specific

Snuffbox mussel

• Endangered mussel found in MI• Need glochidia to attach to logperch,

darters and sculpin• Female attract logperch with soft mantle• When the fish tries to eat the mussel grabs

its head and shoots her glochidia into the fish’s gills

• https://www.youtube.com/watch?v=-1YcaIN8cRs

Riparian Wildlife• Use river and streams as travel

corridors• Rivers and streams provide link

connecting wetland, aquatic, and terrestrial ecosystems.

• Cross over road when no banks present in structure

• Dry passage opportunities reduce roadkill

Bankfull benches in large culverts

How do culverts disrupt stream function?

Geomorphic importance• River can’t flow efficiently through small culvert• Disrupts sediment and organic material

movement• Upstream

• Slows velocity • Build up of fine sediment• Build up of wood and other debris

• Downstream • Increase in velocity • Scours deep pool• Coarsening of substrate • Increased erosive capacity

Geomorphic importance: Example

• Look at up and downstream characteristics to identify undersized crossings

• Stream width• Substrate composition• Bedform structure

• Compliment to visual data to indicate impact of culvert

Cedar River Example

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Upstream Just Above Just Below Downstream

Perc

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Bedform Composition Athey Rd.

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Upstream Just Above Just Below Downstream

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Stream Width Around Athey Rd.

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Upstream Just Above Just Below Downstream

Perc

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Substrate Composition Athey Rd.

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Another undersized crossing

What are we after?

• Natural dynamic stream channel

• Passage of all aquatic organisms

• Low maintenance, flood-resilient road

Sizing and Placement of Stream Culverts

• Match culvert width to bankfull stream width• Extend culvert length through side slope toe• Set culvert slope same as stream slope• Bury culvert 1/6th bankfull stream width• Offset multiple culverts • Align culvert with stream• Consider headcuts and cut-offs

Dr. Sandy Verry, US Forest Service

MESBOAC Example

MESBOAC Example

MESBOAC Example

Stream Simulation Design

• Simulate the natural streambed• Bed shape• Particle diversity• Roughness• Mobility• Forcing features• Control permeability

Slide courtesy of Kozmo Bates, AquaKoz

Culvert Design—Stream Simulation

Slide courtesy of Kozmo Bates, AquaKoz

AOP and maintained stream function benefit aquatic organisms, streams, and humans

1. Less maintenance cost2. Reduced overall long-term cost3. Ecologically the “right thing to do”4. Cooperative funding opportunities

Prioritization and Funding

• RSX inventory• Identify crossing that are

barriers

• Overlap of priority with partner groups

• Work together to fund optimal design

Funding Opportunities

• USFWS Fish Passage Program• DNR Aquatic Habitat Grant Program • Sustain our Great Lakes

Contact Information

Kristin ThomasMichigan Trout Unlimited

616-460-0477kthomas@michigantu.org