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Principle Make culvert NOT a velocity barrier to fish

Principle Make culvert NOT a velocity barrier to fish Compare to typical natural channel hydraulics Use V (section average) as indicator. Design Flow Parameters: Evaluate at Q > normal, Q < flood Choose Q fpd – only exceeded 5% of days Calculate hydraulically (no statistics).

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Principle Make culvert NOT a velocity barrier to fish

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  1. Principle • Make culvert NOT a velocity barrier to fish • Compare to typical natural channel hydraulics • Use V (section average) as indicator

  2. Design Flow Parameters: • Evaluate at Q > normal, Q < flood • Choose Qfpd – only exceeded 5% of days • Calculate hydraulically (no statistics)

  3. YFPD = 0.8 – 34.3S ; min. YFPD= 0.2 Y98 envelope

  4. Backwater from burial – Y up, V down

  5. Backwater effect lost - V > Vch? Backwater from burial – Y up, V down

  6. Velocity Distribution in Culverts

  7. Velocity Reduction Options - Effective • Increase Pipe Roughness – long culverts, steep grades (normal flow) • Use Multiple Pipes – wide, shallow channels; consider drift blockage • Use Wider Shape (Box, Ellipse) – cost vs bridge

  8. Velocity Reduction Options – NOT Effective • Increase Pipe Diameter - mostly air space • Increase Burial – ineffective >1m, ponding, u/s barrier, excavation?

  9. Substrate

  10. Substrate Holders: • Ht. = 0.3m (0.2m for D<3m) • Space = Ht / S (Min. 7m) • Class 1M or 1 Rock Substrate • Only where V > Vch (U/S)

  11. Substrate - Impact on Roughness

  12. Channel parameters: B = 3.0 m, h = 1.5 m, T = 7.0 m, S = 0.012  • Design flow parameters of Qdes= 36 cms, Ydes= 2.25 m, Vdes= 2.8 m/s • Culvert structure: D= 3670 mm, L = 86 m, Burial = 0.925 m, S = 0.012 • For S = 0.012 m/m, YFPDD = 0.39 m, QFPDD= 1.3 cms, VFPDD= 0.9 m/s

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