Members of the Fish Passage Action Team have developed a CFD template  specifically for looking at fish passage. 

Digital modelling lets us look below the surface, at what a single “average velocity” figure never shows.

The surface flow can look far too fast. But look underneath and you find low-velocity zones and resting pools sitting between the baffles. Those are the routes fish use to move upstream. Even at a high flow of 49 CFS / 1.4 m³/s, the velocities through them stay within the range fish can hold and swim against, including weaker swimmers and juveniles.
As flow increases, the surface velocity rises and drags the average up with it – but the sheltered zones below can stay slow enough to remain passable. A single averaged number mixes the fast surface and the slow refuge together, so you lose sight of the passage that’s actually there.

This is where traditional 1D methods fall short. Anyone who’s used HY-8 knows it doesn’t handle baffled culverts well – it can’t resolve the recirculation, the resting pools, or the low-velocity corridors that decide whether a fish gets through.

Whatever passage standard applies in your region, the value of seeing the flow in three dimensions is the same: you assess the culvert against the swim speeds that matter for your target species, not a single blended average.

If you’d like to know more, or have a project you’d like us to simulate, contact the FPAT directly.

The post Exploring Velocities Below the Surface appeared first on ATS Environmental.

Some really encouraging work is coming out of Norway at the moment, with some impressive results to show for it.

Our partner Sweco in Norway have been using FlexiBaffles to restore fish passage in a small urban stream called Fjøsangerbekken, in Bergen. Prior to installation, the stream had been heavily modified through culverting and channelisation, and previous surveys had recorded zero sea trout. It was rated as having very poor ecological status.
FlexiBaffles were installed inside the culvert, creating a series of step pools that allow fish to move upstream.
A year after installation, an electrofishing survey was carried out on a 40 square metre stretch of stream upstream of the culvert. The team caught 123 sea trout, ranging from young-of-year juveniles up to 130mm, indicating the stream is now being used for both spawning and rearing.

Using a conservative estimate, the survey team calculated a density of 127 fish per 100m2, which under Norwegian guidelines would classify the stream as very good ecological status.

It is a striking result for a stream that had essentially no fish the year before.

The post 123 Sea Trout, One Culvert, One Year appeared first on ATS Environmental.

It’s been a while since we last shared any fish passage updates – and this one is worth the wait. With a long weekend ahead, you’ll have plenty of time to dig in!

The reality is that many of our current regulations and the information underpinning them have significant gaps and are overdue for reform.

The Fish Passage Action Team has put together the key principles behind assessing fish passage and designing effective fishways at stream-infrastructure crossings. Drawing on revisited foundational research, emerging knowledge, and extensive field experience, we’ve produced work we think is genuinely valuable:

• Presentation on hydraulic complexity & flow characteristics and how this affects fish.
• Document on reframing fish passage – from single metric & meaningless averages to structured complexity.

­ Click to view presentation ­ If fish passage matters to you and you care about getting it right, please read the document and review the PowerPoint. Then pass it along – to regulators, engineers, ecologists, and practitioners alike – so we can move beyond outdated designs and methodologies once and for all.
­ Click to view key principles document ­

The post Redefining Fish Passage Parameters appeared first on ATS Environmental.

Today we are looking at a couple of examples in Australia where a new type of tide gate has been installed to improve fish passage and upstream water quality.

First up is Cairns, where the site previously used six standard flap gates that were manually held open for fish passage and released during king tides or flood events.
One of these has now been replaced with a fully automated, adjustable stainless steel tide gate.  The remaining gates are expected to be upgraded in the near future.
The next site is in Mackay, where two large wooden gates were replaced with ATS FFGs to improve fish passage and reduce sedimentation through improved flushing.
The concept and function is same for both the Cairns and McKay versions. 
Note: The “double-skin” is for the extra strength required to cover the 3M span.
These two upgrades were commissioned to meet Department of Agriculture, Fisheries and Forestry (DAFF) requirements. 

If you want to know more about Fish Friendly Tide/Flood Gates feel free to reply to this email!

The post Great news! Tide/Flood Gates need no longer be a fish barrier – there is a solution appeared first on ATS Environmental.

Baffles have proven a very effective way for providing fish passage in culverts.

We’ve been hard at work over the past few months developing an interactive culvert baffle design calculator.

We know culvert design can be a tricky subject to get your head around, and we were worried it could be putting some people off. Having seen a groundswell of culverts being designed to improve fish passage, we saw the need for a more standardised approach while still taking into account individual site characteristics.

We’re excited to announce a new resource for fish passage practitioners – the Culvert Baffle Design Tool, created by the Fish Passage Action Team and kindly hosted by ATS Environmental.
­ Click here to try it now – it’s free! ­ This free online tool takes the guesswork out of baffle design for new & exisitng culverts. Enter your culvert characteristics and the tool will automatically generate:

• A set of schematic drawings showing the baffle configuration
• A list of materials required, including baffle sizes, types, and fixings for installation

Any feedback would be most helpful.

The post Awesome Free Culvert Baffle Design Calculator appeared first on ATS Environmental.

Before the holidays, we were on the ground in Gisborne, on the east coast of New Zealand’s North Island, helping kick-start something exciting.

Gisborne District Council and local iwi (the Indigenous Māori tribes of the region) came together for a hands-on training day – learning to use the Structures in Waterways field app to start identifying barriers to fish passage across their area.
The app lets teams assess culverts and other in-stream structures in the field, recording characteristics to help determine whether they’re barriers to fish migration or not. All that data flows straight into a central Sharepoint, building a clear picture of what’s out there and where the priorities are.

But the data doesn’t just sit there. Once structures are assessed, the information feeds into planning for remediation – helping teams understand what materials are needed, estimate costs, and decide where to focus their efforts. 
Gisborne’s journey is just beginning, but to show you where this leads, here’s a snapshot from the Bay of Plenty region, where this same process is well underway.
Every dot represents a structure that’s been assessed. Every dot is progress.
We’ll be following Gisborne’s journey as they build their dataset and move toward remediation. Watch this space.

The post From training to action: Gisborne gets started appeared first on ATS Environmental.

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