Weir’s the Weir gone?

Here at Don Catchment Rivers Trust we have a mission of protecting and restoring rivers in the Don Catchment – this not only includes the Don, but the Dearne and Rother too.

Over the last ten years, we have had a focus on restoring the rivers as a habitat for fish, particularly migrating fish such as salmon. Historically, dozens of weirs were built across rivers to divert water to mills and factories, but this created an ‘obstacle course’ for fish that were unable to swim up and across the weirs. The weirs also fragmented habitats, prevented fish from reaching their spawning grounds, and altered the natural processes a river should have.

Image shows Kelham Island Weir, Sheffield (centre of image, left of the bridge) diverting water from the River Don into an artificial channel called a ‘goit’ above it. This water would have originally powered a water wheel.

Since the trust formed, we have built seven fish pass solutions on weirs along the Don. But we have never had an opportunity to actually remove a weir until recently.

Fish passes can be built on weirs that cannot be removed, such as here at Masbrough Weir in Rotherham. © DCRT

That opportunity arose as part of our Hidden Heritage Secret Streams project at Slitting Mill Weir on the river Rother. The river around Staveley has been altered a lot over the decades to meet the needs of industry – it has been straightened and de-meandered. The original Slitting Mill Weir was several hundred years old, and as the name suggests fed water to the nearby slitting mill, which slit metal bars into rods, to be passed on to other local mills making nails. We know that the Weir was heavily altered, possibly rebuilt using original stones, around the 1950s for the nearby chemical works. Since the works closed the weir has had no use, but remained in the river as a barrier to fish and other wildlife.

Slitting Mill Weir – this weir was once used to divert water to power the nearby mill, but now does not have a function. Weirs such as this are too steep for migrating fish to jump and swim across, so they prevent access to spawning grounds making it impossible for populations to sustain themselves in the river. © DCRT

So, in October, after about two years preparation to get the appropriate permits and planning permission the weir was removed. We understand that this can be quite a sad sight for people who appreciate built heritage, as do we, but the weir was not listed and ultimately we need to right some historical wrongs – all the weirs in the catchment were man-made structures that led to the decimation of the natural environment.

To remove the weir, a small section is first removed to allow the water on either side to level up. At Slitting Mill Weir the impoundment was so large this took 3 hours! After this excavators can remove the rest of the material and even out the bed levels. © DCRT

The weir was removed by using an excavator and the beautiful local cut stone from the crest was salvaged for use by the estate. We opted to leave the stones acting as bank protection in place to serve as a reminder of where the weir used to be. Now, the water level upstream of the weir has returned to a more natural level, and given time the river should start to heal from it’s impoundment.

The river after Slitting Mill Weir was removed, looking upstream. You can see from the banks how far the water levels have dropped – nature will soon repair the bare banks. © DCRT

So, what’s next? Well the team and our citizen science volunteers have been carrying out base line monitoring of the invertebrates in this stretch of the river, so that we can see what impact removing the weir has. We’ll carry on with the post-removal sampling, and will produce our first comparison report in about a years time.

Out team of citizen scientists at work checking on a sample for invertebrates. Currently our samples are consistent with still water or ponds, but now that the weir is gone and the river can flow more naturally we hope to see a change for the better in future samples. © DCRT

Also, now that the water level has dropped, quite a lot of abandoned tyres have revealed themselves! We’ll organise some clean up days once the spring arrives with some dryer weather, and the Covid-19 restrictions allow larger groups to gather.

There’s always a job to do! We’ll make a plan for getting these unsightly tyres removed. Where do they all come from?! © DCRT

There are still more barriers to tackle and habitats to improve on the Rother to allow fish to move up and down the river. Other organisations are working on improvements through the ‘River Rother Restoration’ project, so we hope to see more action soon!

This plan of the River Rother shows the major barriers (red dots) that need a fish passage solution. [to be updated shortly with a green dot for Slitting Mill and Masbrough in Rotherham.] © DCRT