River restoration refers to several different activities that restore the natural state and function of a river. We have been involved in many river restoration projects, from installing fish passes to using green engineering to protect river banks.The River Tyne is home to some of the most iconic fish species in the UK, and human activity throughout the system has influenced their ability to move up and downstream. In particular, obstructions such as bridge footings, weirs and dams can prevent migratory species like salmon and sea trout from travelling upstream to spawn, thereby limiting population strength. In addition, it can reduce genetic diversity and population robustness in non-migratory species such as brown trout.
To ensure the health and survival of fish populations, it is vital that obstructions are removed or altered to make them passable. With funding from Defra and others, and vital help from our volunteers, we are able to perform the required work to improve fish passage.Tyne Rivers Trust has recently led the design and construction of a range of fish passes throughout the catchment.
The nature of these fish passes varies from larger construction projects, such as that at Hexham Bridge, to highly innovative designs that blend into the natural environment, such as those at Lintzford and Stocksfield. The strong fisheries and hydrological skillset of the Trust leaves us well placed to open up more of the river to our valuable fish populations.
Lintzford Fish Pass
Tyne Rivers Trust was commissioned by Groundwork North East and the Environment Agency to carry out a consultation and feasibility study for the creation of a fish pass at Lintzford. This study took place as part of the development phase of the Land of Oak and Iron Landscape Partnership bid. The fish pass was required to allow passage of fish past the 2 metre weir at Lintzford and was intended to inform construction during the delivery phase of the Land of Oak and Iron project.
During 2016 Tyne Rivers Trust in cooperation with its trading company, River Catchment Services led the completion of the construction of a rock pool fish pass at Lintzford Mill on the River Derwent. The works were funded jointly by HLF Land of Oak and Iron Landscape Partnership and the Environment Agency. Construction of the fish pass on the 300 year old weir had a budget of £174,960 was started in early October 2016 and was completed by the end of the 1st week in November 2016.
The fish pass was built directly out from the weir at a 90 degree angle before turning towards the main down-stream part of the river. The left edge of the fish pass followed firstly the existing river bank and then the line of vegetation which also provided protection of the river bank from future erosion during high water events. As the fish pass descended the 2m drop from the top of the weir to the bottom, its width narrowed in order to provide a more focussed attractor flow in low water.
To form the fish pass structure stone blocks known as rip rap weighing between 1.5 and 2 tonnes, similar to those shown in Figure 3 were be driven to the river from the storage area by the dumper and individually placed by the digger using a grab attachment. Although building a fish pass with natural stone is not an exact science, each of the pools between the rock weirs were a minimum of 3m long and the depth was around 600mm in low flow conditions after the placement of the smaller rip rap stone in the base of each pool.
By ensuring the stones were placed tightly together during the construction, water flow through the fish pass would be primarily over the rock weirs during low flows. Flow testing through the pass was undertaken frequently throughout the construction phase by pumping water from above the weir through the pools to ensure that the flow conditions and step heights were as planned. Final ‘sign off’ of each cross weir was done by the Tyne Rivers Trust team with support from the Environment Agency’s fisheries team.
The Lintzford rock pool fish pass project is a fantastic example of what can be achieved through proper partnership involvement. The Trust, the EA and Groundwork worked seamlessly to deliver a fish pass that not only works to deliver improved river biodiversity but also fits into the landscape.
Hexham Fish Pass
Hexham Fish Pass was completed in 2015 and officially opened in March 2016 to coincide with the time of year when spring salmon begin to ‘run’ the river using the fish pass to make their way upstream.
The fish pass is designed to make it easier for salmon and sea trout to migrate upstream to breed. Tyne Rivers Trust has been the driving force behind the project which has taken many years of hard work to come to fruition.
The weir at Hexham Bridge was a challenging leap for migrating salmon and sea trout especially in low water. Many of the leaps were unsuccessful and the fish could injure themselves by landing on the concrete. The energy wasted with these failed leaps also makes fish more prone to disease and they have less energy for spawning when they do eventually get upstream.”
The new fish pass at Hexham gives migrating fish an alternative route, by-passing the bridge footings to swim up two low-gradient channels to continue on their journey up the Tyne.
Riverbank Restoration – West Woodburn, River Rede
The Rede is home to the endangered freshwater pearl mussel, which is susceptable to siltation. Siltation has multiple sources at the landscape scale and this favours using a Catchment Management approach; modifying land use practices to improve water quality, enhance biodiversity and ecosystem services. With the resources available we must be strategic in our site selection, this site was chosen because high levels of livestock aggravated erosion were present.
We used flood resistant stock control fencing to create an ungrazed buffer strip that can better bind soils and intercept farm run-off . Additionally we used ‘soft’ river bank engineering to control excessive erosion. We call this approach ‘assisted natural recovery’, it’s needed where vegetation has diffculty re-establishing. We’ve also used willow spiling and tree planting to kick start the re-growth of the river corridors vegetation structure.
Habitat Improvement – Elsdon
The lower Elsdon Burn tributary of the river Rede was assessed by Environment Agency monitoring as being of moderate status. Suffering from difuse agricultural pressures a number of interventions were designed to have benefits for water quality. Where sheep and cattle were grazing right down to the river, we erected strong flood resistant fencing to promote a buffer strip of taller vegetation. The fence is high tensile post and wire with strong fence post strainers at each change in direction. A cattle access point was created in a suitable location as alternative watering provision was not favoured in this remote location. Timber was utilised to repair trampled river bank and a stone pitched river crossing point allows vehicles, horses and livestock to cross without stirring up sediment.