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Fish passage

Fords

The use of fords across streams can cause similar effects to undersized culverts.

Issues

A ford that has high velocities through the culvert barrel and no wetted margin

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High water velocities – stream flows are often concentrated through one or more culvert barrels, which can restrict the passage of swimming species.

Lack of wetted margins – passage for climbing fish species is usually possible at low flows but not at high flows, unless the ford overtops.

 

Options

  • Ramp fishways – these consist of boulder/cobble or artificial substrate ramps that cover either the whole width or a section of the barrier. They allow fish to swim over obstacles by reducing water velocities, creating resting areas and decreasing the slope.
    Ramp fishways (386.6 KB PDF)

  • Culvert baffling – attaching baffles or artificial substrates to the floor of the culvert/s beneath the ford are effective methods to reduce water velocities and provide resting areas for migrating fish.
    Culvert baffling (180.2 KB PDF)

Note: the pdf documents on this page are excerpts from ARC Technical Report 2009/084: “Fish Passage in the Auckland Region – a synthesis of current research".

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