Dam Removal from UK River: Why Take Out This 200 year-old Weir?

The Wild Trout Trust used funding from The European Open Rivers Programme - a grant giving organisation dedicated to restoring rivers - and liased with landowners, the Environment Agency and The Woodland Trust to painstakingly remove this 4-m tall, 75-m wide weir from Yorkshire's River Nidd.
This "run of river" weir removal is interesting to consider as part of the wider, global movement dedicated to dam removal (including massive hydropower dams).
The weir breached in the floods of 2019 and has been removed safely - rather than left to disintegrate gradually over time, running the risk of causing bankside damage.
Removing Scotton Weir will benefit more than just migratory fish such as salmon and sea trout. All fish move up and down stream to some extent as part of their life cycles and the weir removal will help to restore natural processes to the river - particularly the transport of riverbed material including spawning gravels.
Restoring these natural processes will alter the flow and shape of the river, which in turn will change the nature of the river bed. This will provide varied habitats for invertebrates to colonise, which in turn will provide food for bird species, for instance. This is how restoring a river's natural processes can have an impact on wildlife around the river, as well as in the river and under the water itself.
Currently only 16% of rivers are rated as being in ‘Good’ condition by the Water Framework Directive and a significant cause for failure is man-made barriers interrupting a river’s flow, such as Scotton Weir on the Nidd. Recent research has shown that on average in Great Britain, there is at least one artificial barrier for every 1.5km of stream. In England, Scotland and Wales, only 1% of rivers are free from artificial barriers.
Across Europe as a whole there are in excess of 1 million artificial barriers, which collectively has what the European Open Rivers Programme describes as “a catastrophic impact on biodiversity.”
Free Stock Footage by Videezy!: www.videezy.com

[@oldwaltonian2476]

The WTT is one of the pioneers leading the way in this type of river restoration; the main constraints, in most cases, being the availability of funds. All power to them.

[@WildTroutTrust]

Thank you for such a positive and supportive message. We'll keep doing our best to make funding go as far as possible. Amazingly the project budget of £68K, funded by The European Open Rivers Programme, is actually just a fraction of the average cost of fitting a technical fish pass to a weir on even a modestly-sized river. To put this in perspective, this is thought to be the largest in-river weir ever removed in England - so Prof. Grey and all parties involved deserve a ton of credit. Paul (WTT "Trout in the Town).

[@oldwaltonian2476]

@@WildTroutTrust Most welcome and you are quite correct about the costs. I live next to the Aire in West Yorkshire and a fish pass through the weir (the latter constructed in the 1850s) was completed last year at a cost of £1.3M. Fish passes were also installed at another three weir locations, further downstream, at a similar cost! On a more general note, I am now so passionate about the removal of weirs and other man-made impoundments on our rivers that I no longer have any qualms about the same principles being applied to the ancient structures on many of the heavily 'engineered' chalkstreams in the south; some of which date back to the late 15th century. As important as these may be in a historical context - and I say this as a historian myself - my view now is that restoring the river to its natural state should take priority.

[@davidhussell8581]

Explain your joy. Where is the pros and cons 'balance sheet' ? An adult analysis is required, not mere following of fashion.

[@graememckay9972]

A weir has just been removed on a small river near me. They classed the river as ecologically dead due to slow flow and farm pollution. The weir removal doesn't seem to have changed the flow except a few hundred metres upstream of the weir location.

[@sw8741]

Now now. If you keep thinking like that the magical unicorns and rainbows won't show up.

[@putput3651]

Fantastic stuff WTT! Keep up the good work.

[@WildTroutTrust]

Thank you - we really appreciate your support.

[@richardjones2811]

Jeremy Wade is backing these projects and it's a very good thing to happen.

[@davidhussell8581]

Why ? It was damned for a reason ! Let's have an adult discussion of the pros and cons, not just childish celebrity worship and propaganda.

[@richardjones2811]

@@davidhussell8581It's been redundant for 50 years and only use is to stop migratory fish. You don't need to be a celebrity worshiper to see common sense.

[@robertpatrick3350]

It would be nice to hear some before and after data

[@simonsaorsa]

Excellent. More removals please.

[@WildTroutTrust]

We're working on several at the moment in multiple partnerships Simon, so fingers crossed! Thanks for commenting.

[@mywargoneby]

I wish they'd remove the weird on the esk in east and mid Lothian but apparently one big one also supplies water to a golf course still.

[@lindaj5492]

We’re learning, slowly, but it’s good to see these projects being funded.

[@christopping5876]

Keep up the great work!

[@haroldgodwinson832]

Excellent.

[@jwornell2114]

great stuff, and nice video

[@Zoulstorm]

great work!

[@paulrichardspencer]

Wonderful to see true re-wilding happening, congratulations on completing such a huge project for wildlife and the countryside. As an arborist and amateur conservationist, I'm genuinely impressed by the vision and scope of these works. Now just for the rest of the uk! 🧡

[@simonartley1645]

Great work and thumbs up from a supporter... As always much but good work to do. Always enjoy the magazine and chat at BFFI ..any get togethers or activities in the area happy to help Simon Artley Didsbury Manchester

[@lag9765]

Thank you for doing the right thing. Here in California we are destroying our salmon fisheries because of the greed of the few...

[@luke1023]

Really brilliant we’ll done to everyone who work on this and to get it to happen

[@_starfiend]

It would have been an interesting historical footnote perhaps to have included why the weir was built in the first place.

[@WildTroutTrust]

It used to divert water through Scotton Mill (built in late 18th century). More background and rationale for removal here: www.wildtrout.org/assets/reports/Scotton-Weir-Removal-Press-Release-July-2022.docx

[@_starfiend]

@@WildTroutTrust Thank you.

[@alanfarrance8639]

Interesting video. Annoying music.

[@johnfrench9608]

Amazing great work! MaYbe one day all our rivers will be free of all barriers

[@davidhussell8581]

Great ! Let's flood houses, towns and food-producing farmland, to inflate the price of food and hurt the poorer people, shall we !

[@Clyne-sv4hd]

Good job👍

[@YorkshireDavid]

Better for the canoeists too. Great work.

[@someblokecalleddave1]

Very commendable.

[@garry843]

Why don't they remove the weirs from the Taff, there are no canals on this river, so these could go and give the fish a chance.

[@robertrockwell7581]

the music is louder than your voice. can hardly understand what you are saying.

[@rickwalker7227]

I have just watched your video on the Scotton Mill Bottom weir, one of your first photographs are of my Grandmother and my Aunt and their dog on the weir next to the sluice gate. Where did you get that photograph from?

[@WildTroutTrust]

Hi there, I understand it was supplied to the project by the current owner of the site.

[@rickwalker7227]

I did put the photo on the Knaresborough history Facebook site, so that will be where they got it from. That photo was taken in 1919, approximately

[@Hrodn]

Very interesting video spoilt by the ridiculously loud music.

[@local3433]

What were the results?

[@thezanzibarbarian5729]

Great to see that the river's got it's flow back. But just one question. If the river was damned and not flowing past the original weir, where was the water flowing too?

[@WildTroutTrust]

It was flowing over the top of the lowest points of the crest of the weir (with a large, long still pool of water with little turbulence or energy upstream of the weir).

[@PacoOtis]

Greetings from the States! Congrats on removing the dam, but why the rather horrible music in your video? Best of luck!

[@jimlepeu577]

I wonder, could this clearance possibly prevent floods?

[@WildTroutTrust]

Overall, the impact on either increasing or decreasing flood risk will be hard to detect in this situation. The same amount of water will flow down the river at the site where the weir used to be (compared to the amount that would flow over the top of the weir when it was in place). Also, when the weir was in place, it wasn't set up to create flood storage by deliberately pushing water out onto the floodplain; so that wouldn't have been providing any downstream flood protection. What can now happen is a natural re-emergence of more varied habitat as riverbed material can now be redistributed by spate flows. This was artificially prevented when the weir would, previously, intercept those spawning gravels and cobble materials.

[@teddingtonbear3265]

Fred Dibnah could have completed this work in one hour flat.

[@CS-zn6pp]

He would have dropped it only the bank and built 3miles of dry stone walls from the rubble before lunch.

[@simonartley1645]

Fred Dibnah knew very little about this type of demolition.

[@geoffreylee5199]

If mills et al are gone, removal is best.

[@brianholding4357]

Stupid LOUD backround NOISE WHY!!!

[@vijaysuryaaditya9860]

Look at the positives.

[@bestyoutube5318]

Dont ask. Why England is flooding. Just keep removing the dams and redirecting water 😂 Ya cant make this up….

[@WildTroutTrust]

Please explain how the two are connected?

[@jamesborck5908]

Those tributaries are gone they only existed because the dam

[@stephencrowther524]

Lose the muzak !😢

[@rogerwatkinson6633]

For somebody such as myself with hearing impairment, the music makes it impossible to hear what you are saying. Sorry...

[@petenikolic5244]

Time it was gone we have too many obstructions on our rivers the all need to go for good

[@coolhand6669]

Hey guys I thought that was really great but you know David Suzuki got some high school kids together about 30 years ago in Vancouver British Columbia there was a bunch of old salmon streams never blocked up by crap from the city overgrown trees no way salmon would ever go back up it. And they signed kids from different schools different streams and they worked on it by kicking the trees out and all the blocking material and regraveling the bottom and what they did is they put in fertilized King Salmon eggs into the new gravel in some gravel boxes and a hatched I think it was over a million salmon fry and they came back six years later and it kept up with it and now these streams that never had any returns have returns now that's another thing you could try to do was the Atlantic salmon just throwing it out

[@WildTroutTrust]

There are a number of fascinating complexities to "egg box" schemes and other similar supportive breeding measures - for a more detailed discussion see the article on the Wild Trout Trust main website (particularly "Fact Box 3" covering wild-brood stock schemes and impact on genetics): www.wildtrout.org/assets/files/library/Stocking_position_2012_final.pdf

[@baldieman64]

What's the point? Migratory fish need clean water and silt free gravels to spawn. The River Nidd receives untreated sewage discharges from at least seven treatment works. Calculations based on estimated volumes for four treatment works: Pateley Bridge, Harrogate North, Darley and Kirk Hammerton. Hammond estimated the river received an equivalent of 317 Olympic pools of raw sewage from those works in 2020.

[@WildTroutTrust]

Do you think there is less or more justification for cleaning up the water when barriers are removed (and pollution is one of the final remaining critical issues)?

[@baldieman64]

@@WildTroutTrust I would say that sorting out the water quality has to be the number one priority, because pathogens and sudden drops in dissolved oxygen due to organic runoff are major problems for fish survival and recruitment, along with the silt and bacterial mats. I grew up living near Birmingham's river Tame, and it was regularly subjected to sewage and storm drain runoff during thunderstorms, and these devastated the fish populations. The only places where fish survived these events were side channels and weir pools, where there was more oxygen. Take out the weirs, without addressing the runoff, and you will see entire rivers wiped out.

[@WildTroutTrust]

@@baldieman64 Nobody is suggesting habitat works are done in the absence of water quality protection or improvements. For rivers to survive, they need all three legs of the "milking stool" - which are Habitat Quality, Water Quality/Flow and Connectivity. It doesn't matter which of those legs is missing, the river cannot be healthy. This is why there is a big risk in suggesting that all focus/money should be spent on tackling water quality. Throwing the baby out with the (sewage-laden) bathwater as it were!

[@thomasarmstrong3804]

What's going to Happen during the Next Heavy Downpour, are you going to Have FLOODING DOWNSTREAM

[@WildTroutTrust]

The same amount of water goes over top of a weir as runs down the river without that same weir. What will now happen during large downpours is the downstream movement and replenishment of clean spawning gravel that would previously have been trapped behind the weir.

[@issimondias]

You do realise that the river was there millions of years before the weir was built?

[@tommiles8982]

And what about the eco system that’s just been destroyed? It seems that the species that thrived due to the dam being there have been ignored. Every action has a consequence. I do get that weirs cause obstruction but there are plenty of alternatives which could be implemented such as traps to allow passage upstream. Far better for all concerned and not causing as much cultural vandalism.

[@WildTroutTrust]

What ecosystem has been destroyed? Especially when viewed in the context of the weir (combined with all others built) damaging the river “only” 200 years ago… Compared to the un-impounded river that had developed over the preceding ~12K years since the retreat of the last ice age.

[@tommiles8982]

What ecosystem has been destroyed?! Well I can’t put that better about ignorance than that. You clearly don’t understand action without consequence! The species that live within that niche have a reproductive series a lot less than ours. So 200 years as you put it for the weir (although most have a much earlier date and I doubt that you can be conclusive about this one) is a seriously long time for aquatic organisms that rely and live in these environments. I could go on and on but really. Think about what you are affecting or effecting before making such bold statements. Just to add it has an impact on predators such as birds ie kingfishers etc. So tell me that a trap wasn’t the best solution.

[@tommiles8982]

If you think that I’m taking the micheal, you only need to look at why the Severn barrage wasn’t built.. due to stopping the tidal flow over sites which would expect it and also Sutton harbour in Plymouth, although that one was allowed. So yes ecosystems do exist where you you may not see them.

[@WildTroutTrust]

Thanks for your passionate contribution. One way to put it better would be to explain which particular valuable ecosystem, specifically, has been damaged? I also wonder how likely the ecological consequences of building the weir for industrial purposes were assessed at the time? The science of ecology has progressed quite significantly since the time of construction. If you have an interest in the ecological consequences of weirs, there's an article on our site here which will give at least an introduction to the kinds of things that are taken into account when deciding to remove engineered channel modifications: www.wildtrout.org/wttblog/why-presume-remove-weirs-river-dove-case-study

[@tommiles8982]

Well this is the point I first brought up about that every action has a consequence. Yes I agree that how many centuries ago a major ecological impact was had by the construction of the weir. What I’m trying several times to put to you is that the current (or as in this case past) ecosystem which has existed for a very prolonged period of time (upstream of the weir for 800m as you said) has now been removed. Surely this is just as devastating an impact as construction of the weir all the centuries ago. I get your enthusiasm for righting wrongs and agree in some respects. However we should also consider the environment which is currently established and I personally feel that is what has been ignored. Hence why I was offering a less extreme solution. I feel that getting me to explain what ecosystem is superfluous as that’s exactly what should have been done by yourselves. I’m not an expert nor is anyone else on a section of river bed in a given area unless I’ve studied it, I do however know that such a major change is going to have a major impact, as was when the weir was constructed, as you have said yourselves.

[@derek6579]

God, there are some ignorance people commenting here as each case is a separate issue and geography! Typical woke non scientific comments!

[@exitar1]

Because it doesn't belong there....

[@pauloglesby1117]

Never had any problems before, more WTT shite. Taking gov money to mess about with rivers, net result = ruined fishing because no stocking...

[@tonquinb]

remove all dams

[@ginojaco]

Even hydroelectric ones, and those storing water for population centres?

[@davidhussell8581]

Yes but it was damned for a reason. So what are those reasons and who is disadvantaged by removing this dam ? The lack of facts and the absence of balance in this article, showing both the pros and cons of having, or not having, the dam, all points to this short video not being about truth, but about being propaganda, pushing just one side of the argument. So overall this is a childish video, not one that adults could be pleased with.

[@WildTroutTrust]

It was dammed to serve a long defunct mill. The proliferation of “run of river” dams during industrialisation is a not very well known yet significantly negative impact on rivers and streams. Not only do they fragment breeding populations of a wide range of species by cutting off access, they also disrupt the process of riverbed material transport. This degrades habitat and reduces species diversity as well as increasing the risks of local extinction of certain populations (risking a loss of genetic diversity and the associated resilience/adaptability of native species). The purpose of the video is to highlight projects such as this one. It is part of highlighting these - well established but little known - ecological impacts of weirs. Thank you for the opportunity to continue this exploration of the issues outside of the confines of a video lasting just a few minutes.

[@cedhome7945]

And now beavers are being released to dam the river again.......

[@1738Creations]

Then don't whine and cry when your houses get flooded.

[@CS-zn6pp]

It doesn't work like that. Weirs dont protect from flooding as the water is already full behind it.

[@gordoncrowther7913]

Why do you call it vandalism ? It was vandalism to block it in the 1st place let our rivers run free lessen the chances of flooding

[@WildTroutTrust]

Agreed - that’s what the question mark is for in the thumbnail picture. It’s just that many people would automatically assume that it was a kind of vandalism.

[@djtwo2]

Congratulations: causing more flooding downstream; reducing the recharge of aquifers. You should know that money is being put into projects designed to hold water in the upper reaches of rivers, and here you are deliberately having the opposite effect.

[@WildTroutTrust]

Weirs like this have no effect on slowing the flow (water pours over them at the same rate as if there were no weir there - like a full bath-tub; the exact same amount of water that the taps put in spills over the top). The projects to "slow the flow" are different and are set up in similar ways to natural woody debris dams (along with additional obstacles built out onto the floodplain). The major difference is the way those structures are set up to deliberately flood surrounding land (away from buildings etc.) during periods of high rainfall. The weir in this video did not function in that way (in fact it would have been a much more significant source of problematic local flooding if it did). Also, there seems to be a lot of confusion over recharging of aquifers (which relies on rainfall and soil porosity) versus what run-of-river weirs like this one could do to either help downstream flood risk or aquifer recharge (which is nothing in both cases). As with many things to do with rivers, the effect is completely the opposite of what you'd expect. Rather than storing water, their major impact is to block the transport of riverbed material (rocks, gravels, sand etc.). While they don't change the amount of water flowing downstream, they reduce the variety of current speeds upstream - which creates much more "samey" habitat that can only support a smaller number of species compared to the varied habitat which was present before. Finally, by trapping cobble, gravel, sand and boulder material on the upstream side, the supply of these building blocks of varied habitat are cut off from the downstream reaches.

[@djtwo2]

@@WildTroutTrust So, since you dis not say you has permission to remove the weir, you did not have permission to remove the weir.

[@WildTroutTrust]

@@djtwo2 All necessary permissions were sought and obtained.

[@johnstockburn6396]

Seems strange as I grew up there ,..

[@countrywideboy]

wait till a dry summer.

[@WildTroutTrust]

What difference are you expecting in a dry summer? Do you think all the water would be held up behind the weir like a lake (if it was still there?). If that was true - which it wouldn’t be - what would happen to the riverbed downstream of the weir? Weirs don’t change the amount of water flowing down a river and having a layer of anaerobic silt built up behind them doesn’t do any favours when the weather is hot and dry.

[@countrywideboy]

@@WildTroutTrust short section of river dried up vs very long section dried up

[@WildTroutTrust]

The weir wouldn't significantly change the length of dried up river channel (it might even increase the length of completely dried up channel downstream if you had such extreme conditions that no flow could get over the weir crest). Instead a weir might create a localised increase in the width of wetted channel on the upstream side - but this would also be at the expense of slowing the flow and causing stagnation (which would raise the water temperature). The combination of stagnant flow, increased water temperature and the nutrient-enriched sediment trapped on the upstream side of the weir would strip oxygen out of the water causing fish kills. In contrast, when hot dry weather causes low flows in natural riverbeds without weirs, the flow retreats to the narrowest sections of deepest channel cross section (sometimes known as the thalweg). This keeps a supply of constantly flowing water with higher oxygen levels and a lower risk of fish or invertebrate kills. The benefits of that situation can be increased by making sure there is enough shade from riverside vegetation and that the riverbed habitat is as complex as possible. In higher flows, there is also much better dispersal of nutrient-enriched sediment - instead of it collecting in a large "hot-spot" on the upstream side of the weir.

[@keepmoving.3043]

Maybe you may safe Dover Cliff or contact to other ones. England it is an island whose surface is being eroded. The cliffs of Dover are the best example of this. Submerged breakwaters must be built to reduce sea erosion. Obviously, these breakwaters have to blend in with the environment, so on the surface, they must have a rocky appearance.