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BRISTOL AVON RIVERS TRUST
"A Clear Future for our River"

Bristol Avon Rivers Trust,

8 North Court
The Courtyard
Woodlands
Bradley Stoke
Bristol
BS32 4NQ

info@bristolavonriverstrust.org

 

Donations

BART is a non-profit organisation and all of our work requires funding. If you would like to help us to improve our rivers then please click on the link below:

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Walkover surveys find room for improvement!

BART have been very busy recently, travelling all over the catchment doing walkover surveys and writing advisory reports for river improvement projects including the Corston, Newton, and Nunney Brooks and the River Somer. Jess, our Aquatic Scientist, has found many issues on the Nunney Brook including channel straightening and re-enforced banks which means there is limited bankside and in-stream habitat. She also found sections of the brook were overly deepened, sluggish, full of sediment and heavily shaded, preventing light from reaching the channel. These factors will reduce water quality and productivity in the channel, suppressing invertebrate populations due to lack of habitat and food sources which in turn reduces populations of other river wildlife.

Over-deepend, straightened and channelised section of the Nunney Brook

More survey work took us to a section of the River Avon near Sherston, Wiltshire, where we spent a beautiful evening assessing numbers of spawning Brown trout. We marked the locations of ‘redds’, which are depressions dug by the Brown trout into which they lay their eggs. This survey followed concerns of reduced numbers of the fish each year along with lower water levels. We are planning to put in some woody debris structures here next year to increase the diversity in water depth and flow, which will also help to scour the riverbed gravels of sediment which can smother the fish eggs and reduce spawning success.  To best position the woody debris structures to give the greatest benefit we are going to be monitoring locations of the redds over the winter.

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A beautiful evening for survey work!

Eel surveying on Blagdon Lake

Back in October we worked with West Country Rivers Trust and Bristol Water to begin an eel escarpment study on Blagdon Lake reservoir in Somerset. It was a week of stunning autumnal mornings, so it was a treat to get out on the lake with beautiful views across the misty waters.

The first part of this study investigated the population of the critically endangered European Eel in Blagdon Lake reservoir to see how many eels enter and leave it as they migrate upstream from the sea. This is a crucial part of their life cycle as the eels migrate from where they are born in the Sargasso Sea, across the Atlantic Ocean to the west coast of Europe. From here they travel into estuaries and upstream into rivers where they can spend between 5-20 years feeding and maturing until they are ready to migrate back downstream to the Sargasso Sea to spawn. Barriers to migration are one of the main challenges that eels face, which is why this study is so important as it will show whether the eels are able to survive in the lake and eventually exit it as they migrate back downstream.

Fyke netting

We used Fyke nets to fish for the eels overnight, which trap the eels as they swim into them. The nets do not harm the eels in any way, but simply prevent them from escaping until we come in the morning to count and measure them.  Measuring the size of the eels will help us to age them, which is important to know as it tells us the stage of their life cycle. This project will help us to find the best ways to help this endangered species, so watch this space for more eel related research!

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Working with Wiltshire Wildlife Trust

Here at BART we like to give other ‘watery’ organisations a helping hand, so we spent a couple of weeks with the Wiltshire Wildlife Trust Water Team to help out with some of their river restoration work. We worked near Salisbury on the River Bourne, the River Nadder and the River Avon, installing woody debris to improve habitat and channel sinuosity in over-widened and over-straightened channels.

 

In some places there was no in-stream habitat available at all for invertebrates and fish, shown in the photo above, where a concrete wall has been used on one side of the channel. Installing woody material at the base of the wall will help to reduce erosion and protect the bank, provide shelter for small fish and help to trap any suspended sediment in the water column to prevent it settling and smothering the riverbed gravel.

We also carried out bank improvements in places where the river was beginning to erode a public footpath. Using the technique of hazel weaving shown above, we constructed a natural bank protection feature which was then back-filled to create a much wider bank, safer footpath and prevent further erosion.

Thanks to Wiltshire Wildlife Trust for having us along, it’s amazing to see how much we can achieve by working together with the support of a great team of volunteers, we couldn’t have done it without them!

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A month on the Wellow Brook

After working on the Wellow Brook for the whole of September we have finished this section of river restoration work! We have had a fantastic few weeks building in-stream habitat structures in Somerset at Midsomer Norton and Stoney Littleton, which will provide habitat for juvenile fish, scour sediment from riverbed gravels and create flow diversity by forming shallow areas and deeper pools.

In total we built 34 structures which is a tremendous achievement!

A completed woody debris structure

The woody debris structures, made from coppiced trees from the riverbank, will gradually accumulate sediment over time which will re-meander the channel within its banks and re-naturalise the stream. Within a few days we could already see sediment accumulating on the structures and the river meandering around them, so we’re looking forward to monitoring them in future. Re-naturalising the channel will improve habitat for invertebrates and fish, and therefore benefit all of the other wildlife which relies on this river too.

Volunteers at Midsomer Norton

BART would like to say a huge thank you to all of the volunteers who got involved in this project, without you we could not have achieved anywhere near as much as we did! Building the structures is hard work but all of our wonderful volunteers were happy to get stuck in and remained enthusiastic, even when it rained!

Working hard to secure those posts!

Another thank you to the Environment Agency Asset Performance Flood and Coastal Risk Management team who joined us for a day at Stoney Littleton, you were a great help!

Happy volunteers!

We hope to keep working on this stretch of river, and are continuing to look for further opportunities where improvements can be made…so watch this space!

A final thank you to our funders who made this work possible. To the People’s Postcode Trust for funding the restoration work in Midsomer Norton, and the Environment Agency and Bristol Avon Catchment Partnership for funding the work at Stoney Littleton.

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Bringing back curves to the River Biss

September is always a busy month for BART with fieldwork and river restoration, and this year was no exception. As we need to avoid the trout spawning season which begins in October, September is always jam packed with long days out on the river and we have definitely been making the most of it!

Over the weekend BART have been doing river restoration with the Friends of Biss Meadows Country Park in Trowbridge. They are a community conservation group formed of dedicated volunteers who protect the plants and wildlife at the country park. They also run wildlife walks throughout the year and have monthly working parties so are kept busy all year round!

Working together with the Friends group and other volunteers we restored in-stream habitat diversity to a section of the River Biss, which created a more diverse flow within the river channel which had  previously been overwidened and overstraightened. The berms which the volunteers built will create new areas of habitat by forming shallower bays which will gather sediment and form new areas of bankside, as well as faster flowing sections of the channel which creates flow variety.

The team built woody debris structures out of coppiced tree limbs which are then fixed into place by the bank using chestnut stakes. The tree limbs are angled into the channel and brash cut from the tree limb fills in the structure from the bankside.

These structures will provide refuges for juvenile fish as the river slows as it flows through it, and acts as a nutrient trap where the water is warmer which again gives juvenile fish a helping hand in finding food. The structures also trap silt which would otherwise be suspended in the channel, and promote scouring of silt from gravels on the riverbed which is essential for fish spawning.

The conditions were pretty tricky to work in with deep water full of silt after the recent heavy rain, so an extra well done and thanks to all the volunteers and the Friends of Biss Meadows!

Thanks to People’s Postcode Lottery‘s Awards for All for funding this project with Friends of Biss Meadows Country Park.

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