Skip to main content

Wandle update - weir'll meet again.....

A quick one to make up for the lack of posts recently (I have been furiously drafting the upcoming "Urban river restoration guidelines" manual for publication this summer......)

This one is about weirs (again - see "weirs tha bin?" previous blog post)

I've lost count of the number of times that angling club members have been scared to death by the suggestion that a weir is taken down - Understandably - because often the foot of that weir (and the attendant scour hole) forms a weir pool that has the best fishing on that section of river...

Thanks so, so much to Theo and the Wandle piscators/Wandle Trust for having the faith in our advice - it is by weir lowering or removal that the single good fishing spot BELOW a weir can be transformed into tens (hundreds?) of good fishing spots above the weir! All of that current velocity that is killed behind the structure (causing silt to gather) is re-invigorated throughout the whole reach. This will clear away the silt, expose spawning gravels (and habitat for more invertebrate species) and also provide the energy to produce localised scour pools all along the river which will hold fish all the way up the reach.

In at least one study of weir removal - TEN TIMES the BIOMASS of trout and salmon were found following weir removal (compared to the biomass when the weir was in place). This is a far, far, far bigger effect than installing a fish pass (which is sometimes your only option - but is never perfect because only a proportion of fish will find and navigate them, and it also has no beneficial effect on the habitat above the weir).

A huge well done also to Tanya Houston in E.A. fisheries for getting the permissions in place and also marshalling staff/volunteers to begin taking down these key barriers (course by course!).

Here are the effects of the removal of the first tier of stones from one of the Wandle weirs:

A smallish example - but one which makes free upstream movement for fish difficult (or impossible for some). It also has accumulated a lot of silt behind it.

And here is the same weir with the top course of stone removed and a notch taken out at the near bank side. Note the large ramp of clean gravel below the weir - this now has water percolating upwards through it from the bottom of the scour hole beneath the structure - excellent spawning habitat

Contrast this with the situation just above the weir BEFORE the stones were removed - ankle to mid calf-deep in grey silty sediment (including road runoff):

Now, with just the top course removed and notched, this section is bright clean gravel with a good current flow. Ripe for trout colonisation - especially with a little small-scale LWD introduction to encourage mid-channel scour and overhead cover (note the tree towards the centre of the frame - this is the same one that Theo is standing - in silt - in front of in the previous photo):

Comments

Willowbank said…
Great post, very good example.
Darrell said…
I love this project. I am coming to the UK for the Fringe in Edinburgh, then fishing through the UK for 10 days. I would love to donate time and assist in a project, clean up, structure work, anything. I am from Los Angeles, and my friends and I work to preserve and restore our trout waters. We do have them, and close to town. Thanks, and plese keep up the good fight.

I can be reached at

flykuni@gmail.com

Darrell K.
LA, Cal.

Popular posts from this blog

A previously buried section of stream produces the first fly caught trout in >160 years

As near as I can work out from the archaeology report, this section of river - recently brought back to the surface in dramatic fashion by Sheffield City Council, the EA and the WTT partnership - was buried in a low brick tunnel somewhere around 1853 to 1868. The northern half of the site was certainly buried underground BEFORE the time the 1853 map was produced....and the rest of the brick tunnel was placed over the top of the stream before the map of 1868...

Of course, it is not easy to tell what the water quality was like in that section even BEFORE the stream was buried...and whether there were trout surviving in the stream when it was sealed underground...

What is damned sure is that you couldn't wave a fly fishing rod around in that underground tunnel once they'd built it!

This was still the case until the completion of the massive project to remove the brickwork and create an attractive "pocket park" in the city centre. You might have seen from This Previous …
Catching and Releasing the first Fly-Caught wild trout from a stream that was dug out of a city-centre pipe was probably the highlight of 2016 for me!

Buried in a brick tunnel under England's industrial developments of the 1800s, a section of the Porter Brook in Sheffield was brought back to the surface by a bold project co-ordinated by Sheffield City Council and involving the Wild Trout Trust, The Environment Agency and many more partners.

You can now witness the actual process of freeing the Brook from its pipe - and the creation of functioning trout-stream habitat in this short video.



Yet, the above video does not show the completed park that was a huge part of the entire project - and it does not show the planted vegetation beginning to develop in the summer of 2016. And, it does not show any fly fishing or video of a trout capture...

But the film, below, that was made by the excellent Huckleberry Films as part of the Canal & Rivers Trust "Living Waterways" awar…

Buried Stream Project Wins National Prize

I'm delighted to say that the Porter Brook Deculverting project was selected as the 2016 Winner in the Canal & Rivers Trust for "Contribution to the Built Environment". This was a multi-partner partnership project (with key involvement of Sheffield City Council, the Environment Agency and more) that I was fortunate to have the opportunity to design the in-channel habitat features to provide the best functional benefits for trout and the wider aquatic foodweb. The Sheffield Branch of Trout in the Town "SPRITE" are caring for the habitat as well as monitoring the aquatic life in this new section of daylighted urban stream.

As well as my previous blog posts on the subject, the awards scheme made short videos (less than 2-minutes) long that captured key elements of each project entry. You can see the film for the winning Porter Brook project below. Please enjoy and share (and also check out the other project videos on YouTube from this year's awards).