Beckfoot Mill Weir on Harden Beck was independently identified by both Kevin Sunderland of the Aire RT and the Environment Agency as an obstruction to fish passage and an interruption to natural geomorphological process. EA fisheries data confirm that grayling are only recorded in the beck up to the weir, and since it is only ~750m from the confluence with the Aire, modification of the structure potentially opens up several kilometres of quality habitat for them, as well as improving connectivity for the local trout populations.
The weir no longer functions to supply a goit with water, and the owner was in favour of the ecological benefits of the proposed project from Professor Jonny Grey of the Wild Trout Trust. Jonny’s plan was to remove one or two of the large gritstone blocks and focus all the flow under low flow conditions through a gap, thereby removing the head drop of 40cm and the 50m impoundment of water upstream which has infilled with bed substrate over the years to become very shallow and of little use as habitat.
Beckfoot Golf Club, riparian owners on the right bank, was consulted by Kevin and gave its support. The project application was also assessed for flood risk by Bradford Metropolitan District Council (since the beck is not classified as main river) and approved. From a biosecurity perspective, the weir was identified as easily passable by invasive crayfish and hence not a potential barrier to their spread, by an EA crayfish expert, and Jon accompanied them on a torchlight survey on June 21st to determine their presence above and below the weir; none were found thankfully.
Last week, in a gap of good weather and hence low flow, work began. To minimise disturbance to the bed above, and the riparian trees, a 5-tonne digger was substituted by a jack-hammer, a Stihl saw, a 2m wrecking bar, and a lot of brute force! One block was broken up and all the material moved downstream to contribute to the natural substrate. A second block was loosened and will be moved further into the former weir pool to widen the gap, once the bed upstream has adjusted.
By the late afternoon, the beck was actively cutting down into gravels, cobbles and boulders that have probably not seen the light of day in decades. What was a shallow, almost stagnant pool above the weir is now a meandering riffle and there was a noticeable drop from the impounded level of ~10cm as measured by watermarks on large boulders almost 70m upstream. At the weir itself, there is no longer any requirement for fish to leap, and there is now a focal flow of deep water instead of the energy being dissipated across the full width of the weir and resulting in a v shallow skim of water which fish find difficult to negotiate in either direction.
This is just one of a series of low-head weirs throughout the catchment to be made more passable using funding held by Aire RT, and in partnership with the Wild Trout Trust and the Environment Agency.