river restoration round up: October edition

Welcome to the October edition of River Roundup, where we dive into the latest updates from North Wales Rivers Trust’s river restoration and fish passage projects. This month, we wrapped up our in-river works just in time for the salmonid migration season. These efforts have been all about giving nature a helping hand—taking out barriers, improving fish passage, and enhancing habitats so our rivers can better support biodiversity. Let’s take a look at what’s been accomplished!

1. Weir Removal on a Clwyd Tributary

Before After

We completed a significant partial weir removal on a tributary of the River Clwyd. After a SNIFFER in-river barrier assessment confirmed this weir was both a partial and total barrier for various migratory and coarse fish, we removed 50% of the structure and added a rocky ramp to maintain the necessary head difference to prevent any cut back (vertical incision) upstream. The rocky ramp provides pools and increments to break up the total height difference. This improvement will make a real difference for fish populations, granting them improved access to an additional 2.3km of viable habitat.

2. Afon Seiont Habitat Improvement Scheme

In the Afon Seiont catchment, we’ve been working on a crucial habitat improvement scheme for this important salmon and sea trout spawning river. The Seiont has several prime spawning sites, known for their loose gravel and pebble substrates, optimal flows and good overall habitat for salmonids. Unfortunately, one of these sites has faced degradation over the last decade due to upstream nutrient inputs and a lack of active management. This led to the growth of in-river plants and encroaching riparian reeds, usually only found in still water, which smothered the gravels and reduced flow diversity.

With the help of dedicated volunteers, we gave this site some much-needed TLC. We cleared the encroaching reeds, removed excessive in-river vegetation to reveal the vital gravels beneath, de-compacted the gravels across a 2800-square-meter area, and introduced boulder clusters to diversify flow types and provide fish refugia. These changes create a more hospitable spawning environment, and we’re excited to return this winter to see salmon and sea trout making use of these improved grounds!

3. Enhanced Passage on the Llyn Peninsula

On a river on the Llyn Peninsula, we have been busy improving fish passage at a challenging weir composed of cobbles and concrete capping with a head (height) difference of around 0.55m. The aim of this scheme of work was to remove the eroded concrete capping and rearrange cobbles of the weir structure beneath to create a natural rocky cascade, thus increasing the number of potential routes for fish passage and naturalising the physical habitat and flow.

Previously, fish could only attempt to pass through a broken section on the right bank, a narrow and challenging route with small boulder steps and limited resting areas. By enhancing this passageway and ensuring flow depth in key areas, fish of all sizes can now migrate through during lower flows. This work not only facilitates fish movement but also helps maintain the downstream supply of spawning gravels, an essential resource for healthy fish populations. Fish now have improved access to 3.8km of habitat upstream. 

4. Afon Eden Habitat Restoration

The Afon Eden saw substantial work this month, with over 100 boulders reintroduced into the river channel to diversify flows and create habitats for fish and invertebrates at one site. Many of these boulders were previously dredged to construct embankments, and reintroducing them now brings new life to previously featureless sections of the river. Boulder clusters have been created, providing much-needed refugia and improving habitat complexity.

5. Phase 3 River Restoration on Afon Eden

On a protected site along the Afon Eden, we continued a multi-phase restoration project with critical habitat improvements. After phases 1 and 2, which included over 2 km of riparian fencing, a newly established buffer zone of 10m, planted with trees for cooling and bank stabilisation, this month saw us complete all of our in-river interventions for phase 3. We introduced an additional 100 tonnes of spawning gravel and 60 boulders to enhance habitat diversity and flow. 

To further boost biodiversity, we trialled several natural flood management techniques, including swales, depressions, and bank reprofiling to reconnect the river to its historic floodplain. These features will help regulate flows, support a variety of habitat types, and enhance ecosystem resilience in the face of climate change.

Looking Ahead

With October behind us, we’re now preparing for the seasonal migrations and are excited to see the results of these projects in action as fish return to these newly accessible areas. Stay tuned as we continue to monitor and report on the impact of our work. And as always, we thank our partners, supporters, and the community for helping us restore and protect North Wales' rivers!

Be sure to stay tuned as we progress with our out-of-river projects this winter! 

This work has been completed thanks to fisheries funding in partnership with Cyfoeth Naturiol Cymru / Natural Resources Wales and Local Nature Partnership funding in partnership with Snowdonia National Park.