Fish Easements
Barrowford 2010
One of the Trust’s larger scale projects, the modification of the weirs at Barrowford, opened up Pendle Water, a main tributary of the River Calder, in order to allow fish to migrate further upstream. The lowermost weir was the smallest and work involved simple chipping away of the concrete to improve fish passage.
The weir upstream required an additional low concrete weir to be installed on the front of the existing one in order to raise the water level. In doing so, the fish were provided with sufficient take-off depth from which to jump. Several large stones were placed 8m downstream again to raise the water level in front of the new low weir. This work made the whole lower weir system passable to fish in all flow conditions.
The upstream weir however was on a much larger scale and a fish pass was set into the weir itself. A fish pass is a concrete structure consisting of a channel that fish can easily swim through, allowing access to spawning ground in the upper reaches of the river for migratory fish such as salmon and trout. The removal of the series of barriers at Barrowford will also increase the biodiversity in the upper reaches of Pendle Water and create a much more varied and sustainable ecosystem.
Swanside Beck Fish Easement, April 2010
The weir on Swanside Beck at Rimington already had a fish easement installed, however surveys upstream from the weir resulted in poor fish counts which suggested the fish easement was not working as intended. Originally there was a large lip at the bottom of the weir that would have made it difficult for fish to clear. In an attempt to try and improve the situation, the Trust constructed a secondary horseshoe-shaped stone barrage 12m downstream in order to raise the water level sufficiently to cover the lip at the base of the main weir. The hope is that with the higher water level, migratory fish such as salmon and trout will find it easier to ascend the existing fish easement without injury or undue stress, allowing them access to spawning grounds further upstream.
West Bradford 2010
Over a decade ago, a fish pass was privately installed on a weir in West Bradford Brook in an attempt to allow salmon and sea trout passage to the upper spawning waters. Unfortunately, the Trust found that the fish pass was not working due to its poor design and after careful deliberation, the decision was made to remove the fish pass and demolish the weir altogether.
The concrete was disposed of off site and the banking was reworked and reinforced with cobbles from the stream to create a slope down to the lower water level. In time, this banking will naturally re-establish itself with vegetation.
Weirs aren’t just barriers to fish; they also retain gravel, preventing it from naturally washing downstream. This results in a distinct lack of substrate downstream of the weir which does not provide good habitat for fish. With the removal of the weir we expect the stream to return to a more natural state, resulting in a much more ‘fish friendly’environment.
Padiham Weir – Completed in 2010
Around 30 weirs have been identified on the Calder system that pose significant barriers to fish migration and Padiham Weir was one of the largest. The Trust has carried out modification of this weir by installing a rock ramp style fish pass, the beginning of the Trust’s attempt to open up a further 20% of the Ribble catchment to salmon, trout, grayling and eels for the first time in decades.
Padiham weir removal has been one of the Trust’s greatest success stories, fish of all species and ages are now able to pass the weir in all flow conditions. The increased number of fish in the upper reaches will in turn lead to a greater variety of wildlife such as kingfishers and otters, hence creating a much more biodiverse and sustainable ecosystem. As well as this, it is anticipated that there will be greater investment in fishing clubs/riparian owners, with a knock-on effect for the local community in terms of a much more attractive environmental asset in which to fish, walk and bird spot.
Eel Beck 2010
Eel Beck at Rimington is a small tributary of Swanside Beck, which feeds directly into the River Ribble. Despite being a very small beck it is nonetheless vital to the Trust as streams like these constitute the ideal spawning grounds for fish, in particular Salmon and Sea Trout. Unfortunately there was a rather high, redundant concrete weir situated on Eel Beck which made it impossible for any species of fish to migrate further upstream. Not only this, but the weir unnaturally retained the smaller substrate upstream and caused substrate scouring further down.
The proposed plan of action was to completely demolish the weir, breaking it up into large blocks so as to keep sediment to a minimum. Once the weir was removed, gravels and substrate taken from upstream of the weir were selectively replaced on the stream bed with the aim of allowing the beck to return to its natural state. The removal of the weir has opened up a larger area of spawning ground for fish, consequently producing an increase in biodiversity.
Montford Weir 2010
Another redundant Calder barrier which was reduced in height by removing and re-shaping some of the existing stone blocks that comprised the weir. The removed stone was placed downstream in order to deepen the pool below the weir so that the fish would have a sufficient depth of water from which to clear the remaining obstacle. The work was done during low flow conditions and a sediment trap was used to prevent too much silt polluting the water downstream. The removal of the weir resulted in a faster flow and a lower level of water, leaving some of the river channel exposed. New vegetation has begun to grow on the exposed banks, providing better habitat for birds and river dwelling mammals.
The removal and modifications of these weirs will provide migratory and non-migratory fish access to the upper reaches of the catchment, which will in turn lead to a greater variety of mammals, birds and invertebrates in the upstream river habitat. We expect that fishermen, walkers and birdwatchers alike will be able to take full advantage of this newly created biodiversity.
