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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 21^st 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.

Aire Rivers Trust has agreed to fund work to improve fish passage and reinstate connectivity on several small to medium-sized weirs on tributaries between Bingley and Malham. The work is being coordinated by Professor Jonny Grey, Research & Conservation Officer for the Wild Trout Trust, in partnership with the Environment Agency and various other organisations and land-owners.

Ideally, these redundant weirs would be removed completely to reinstate a more natural channel form and flow of water, plus transport of material (cobbles / gravel) downstream, and reduce flood risk. However, other surrounding infrastructure that potentially could be affected by complete removal requires some thought. The proposed solution at each weir varies slightly because of the differing nature of each beck and immediate environs. Most will be ‘notched’ in some format, i.e. the crest of the weir will be lowered in a specific location to create a focus of flow during low flow conditions.

Eastburn Beck has been a particular focus for related work (see blog post, here). The last in a series of privately owned weirs just below Glusburn Bridge was notched in May. Jonny noted that there were trout fry in abundance during the works – a good sign of the population bouncing back from the previous year’s unprecedented flooding that effectively scoured out all the eggs and juveniles. The weir owner was delighted! The notch will allow them better access both up and downstream, and also reduce the amount of stagnant water and silted sediment upstream in the formerly impounded section.

Image (1&2): Eastburn Beck weir, pre and post notching

Kirkby Beck is much smaller than Eastburn, and much higher in the Aire catchment at Hanlith. The weir is less than 10m upstream from the confluence and hence is an immediate obstruction on the system. The local farmer agreed to a notch and several hundred metres of fencing to prevent livestock access from degrading the beck banks, thereby improving the habitat at the land water interface for birds, mammals, insects and plants, as well as fish. The work was carried out in May when the beck had all but dried up! The aquatic organisms living in such ephemeral streams have evolved to cope with occasional dry periods in all sorts of ways; with a notched weir, now the fish can recolonise more easily after having migrated downstream to avoid the low flows.

Two hydros and fish passes are under construction on the lower Aire.

Chapel Haddlesey

The turbines have already been installed and the baffles for the fish pass will be delivered in early June 2017. The fish pass and the two Archimedes Screws are expected to be in use by the end of June.

Knottingley

The two Kaplan turbines should be delivered in the near future. Work is still being carried out on the walls of the chambers. The photo shows the huge size of the chambers. Some earthwork has been prepared for the site of the fish pass but, as yet, the concrete base has not been laid. The fish pass will be a two flight one having a single resting pool. The latest date for expected completion will be some time in the autumn of 2017.

Sustainable Urban Drainage Systems (SUDS) are much talked about these days, but  what are they and what is the point of them?

Sustainable drainage mimics natural processes and reduces flooding by managing rainfall close to its source and wherever possible at, or near the surface. By building in permeable paving, channels, green roofs, swales, soakaways or ponds, sustainable drainage becomes a “city circulatory system”, slowing, storing and treating water that could cause damage. Well-designed SuDS should incorporate the four elements of water quantity, water quality, amenity and biodiversity wherever possible. They are fundamentally a way of slowing and reducing surface runoff in order to reduce flood risk, whilst at the same time improving the look of the urban environment.

Now CIWEM (Chartered Institution of Water and Environmental Management) recently published a very well-researched and informative study on the subject which supports their wider implementation:

Incorporating SuDS into developments can maintain local water balances and treat water pollution, whilst also supporting wildlife and delivering attractive community spaces

 

It’s well worth a read, so here’s a link to a copy for you to download.