“Restoring fish passage and reconnecting waterways – it’s our passion”
Changing the narrative towards mass remediation across infrastructure networks.
Everyone passionate about restoring fish passage and reconnecting waterways should take the time to sit in on this webinar. https://www.eianz.org/events/event/webinar-managing-assets-with-respect-to-meeting-fish-passage-requirements It is on Wednesday 9th March – 3 PM NZDT
Further to our recent mailout where we discussed mussel rope at perched/overhanging structures, it’s now time to look at mussel-rope when placed within culverts.
Mussel-rope is one of the tools that can be used to help improve fish passage where fast, laminar flow is present.
If it is not viable to remove an existing culvert or is not practical to fit baffles due to the small diameter (e.g. under 750mm or 2 &1/2 feet), then mussel-rope can be considered as a remediation tool.
Obviously, the rope does not retain bed material, create rest-pools or the complexity that baffles do. Therefore rope should only be used as a last resort, and it should not be used at new culvert installs.
Below are some CFD images that show the effects the mussel-rope has on the depth and velocity in culverts.
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Understanding Mussel-rope Part 1
Many culverts are barriers to fish due to being perched/overhanging or having fast laminar flow.
In the video below, Tim demonstrates how mussel-rope can improve fish passage at perched/overhanging structures.
The rope simulates natural tree roots and fibres that some species have evolved to utilise when migrating upstream.
The type of rope being used here is “looped mussel-rope”.
Looped rope is proving to be an effective remediation tool at perched/overhung structures. It also has the benefit of not shedding fibres as readily as other types of ropes.
| Hi everyone The Fish Passage Action Team have been working on a simple one-page guide to help with the remediation of common structures causing a barrier to fish. The guide includes a link to an interactive decision tool and some helpful before & after examples. Happy holidays! |
 Fish Passage Remediation (existing structures) Overview Fish passage remediation is less about target species, specific swimming speeds, average velocities, Mannings numbers etc., and more about understanding the medium in which fish have evolved to navigate, i.e. water, with the dynamics of complex flows and boundary layers all at a fine resolution. Basic principles – “Match or better” the streamflow characteristics. – Provide complex flows (non-laminar) – multi-directional flows with rest pools. – Length of fast flow zones between rest pools must be shorter than fish burst-swim capabilities. – Provide sufficient depth. – Ensure continuity – no overhangs. – Give fish a range of navigation path options. – Ideally, retain bed material. General rules. – Rope should not be used in culverts if baffles can be fitted, even if climbing species are targeted. – Ramps should include splash zones and substrate, e.g. rope. – Ramps should extend into the plunge pool as far as practicable. – Baffles should be spaced so that the rest pool from one extends easily up to the next. – Baffles may be considered artificial bed material in some situations, i.e. create similar hydrological conditions – If rope is fitted through a culvert that is also perched, a second set of rope should be fitted at the outlet. – Rope should only be attached at the upstream end. – Interventions should not significantly reduce culvert capacity or increase the risk of debris jams. – Tide-gates should be designed/modified to delay the closing as long as possible. Which tools to use where? The above principles help to guide us towards selecting appropriate remediation tools. For more detailed guidance on the use of remediation tools click here: Remediation Decision-Tree Interactive Tool Before & after examples click here:https://www.ats-environmental.com/before-after-remediation/ Measures of success: Success should be outcome-focused and easy to measure or observe. – Complex flows similar to stream (depth, width, velocities) – Bed material retained. – Continuity – no perch or overhang. – Extended opening period for tide gates. Please note that the linked resources above are kindly provided by ATS Environmental. |
Hi everyone,
We hope you are staying safe and well.
As shared a short while back, we have started using Computation Fluid Dynamics (CFD) to solidify what we already knew about culvert/weir baffles and their fish passage improvement features.
CFD is a powerful engineering tool used to simulate the action of fluids in a structure at a resolution not normally visible to the human eye.
It is well known that fish prefer deep water, complex flows and lower velocity, so it is exciting to see just how much of an impact different types of baffles have on the flow dynamics.
The independent CFD simulation was able to demonstrate the depth, and changes to velocity, with and without baffles installed.
The baffles included in this study were, Type 1 Spoiler Baffles, Type 3 Spoiler Baffles and Flexi-Baffles.
Below is a link to a Glide-show and we hope you find it as interesting as we did!
Contact the Fish Passage Action Team if you want to know more, and perhaps run a simulation on a structure that you are planning to remediate.
Hi everyone
Below is a photo showing modifications to a back-country mini-hydro intake weir.
The original fish pass and minimum residual flow devices were not functioning.
The new design successfully allows expected species, all of which are climbers – longfin eels, and some migratory galaxiid along with invertebrates, to migrate upstream.
The fish passes comprise a flexible rubber channel (2 x Flexi-baffles) lined with looped mussel-rope. The rope is only attached at the upstream end to avoid debris jams.
The Minimum residual flow is controlled by another flexible baffle that pushes water to sides before overtopping.
Please contact the Fish Passage Action Team for more detailed information.
Hi everyone
Below is a YouTube link to a video sent to us from Greg Wallis in Australia.
It shows common galaxiid/inanga (Galaxias maculatus) trying to navigate a vertical wall at a large box culvert.
Despite these fish showing amazing burst-swimming abilities to scale parts of the vertical wall, very few were successful.
Sadly (for the fish), many were picked off by an opportunistic heron.
Simple solutions such as baffles and ramps could vastly improve fish
passage at this culvert.
Enjoy
Hi everyone
Following the restoration of fish passage into the Pongakawa Wetland (Bay of Plenty, NZ), the upstream habitat has been further enhanced by deploying Floating Nurseries that provide shade and refuge for aquatic and terrestrial species while also improving water quality. Click on the link to the Glide-show – Enjoy!
Link to glide-show: https://spark.adobe.com/page/U2jng2H1a7oXB/
Hot off the press
Tim’s short video showing a family of grey teal ducks (pārera)
using a Floating Nursery – literally! https://www.youtube.com/watch?v=KvV2W0n2tHo
Hi everyone
It is widely believed that eels can cross land between water bodies however little is understood as to how or why.
This rare footage captured by Tim Olley shows a medium-sized NZ Longfin eel taking advantage of a flood event to migrate upstream across what is normally dry land.
Much is known and documented about juvenile eel migration, but less so for adults.
Note how the eel is using burst swimming between long rest periods as they do in natural settings.
Less vegetation and an unnatural stream bed means that eels have to work harder when migrating in such situations.
Also, due to a lack of cover, eels are very susceptible to predation from birds at these times, as we have witnessed.
Do older shortfin eels have this upstream migratory urge like longfins?
Enjoy:)
Hi all,
Some of the Fish Passage Action Team were recently involved in a very satisfying restoration project.
It is rare that we get the opportunity to completely remove culverts in an effort to restore fish passage so we wanted to share this with you.
See what two workers and a small excavator can manage in a day.
Alex put together this short “Glide-Show” so you can scroll through it at your own pace.
