Langsett fish pass


All over the world, the migratory movements of fish species are blocked or impeded by man-made structures. World Fish Migration Day on 21 April is designed to highlight the work being undertaken to mitigate this impact.

Langsett weir is located upstream of Langsett Reservoir, on the River Little Don, northwest of Sheffield. The reservoir contains a large population of resident Brown Trout (Salmo trutta), however the best spawning habitat for these fish is located upstream of the weir. Therefore, the weir forms a barrier which limits the sustainability of the trout population in the river. As the owner of the weir, Yorkshire Water committed to installing a fish pass on the weir as part of their AMP6 funding cycle.


Following a feasibility study, a double flight Larinier fish pass was agreed with the regulator and client team to be the preferred option. Appointed to undertake the detailed hydraulic and structural design, we acted as Principal Designer and subsequently covered the site supervision during construction.

The design had to balance a range of technical and health and safety constraints:

  • the low flows at the site meant that the pass needed to be narrow
  • there is difficult access to the site
  • its proximity to a Site of Special Scientific Interest (SSSI) and Special Areas of Conservation (SAC)
  • the site is popular with walkers and swimmers (on hot days!).

The project team consisted of hydroecologists, civil, structural and geotechnical engineers, together with the Principal Designer who worked closely with the client team to balance these constraints.


Health and safety risks associated with maintaining a 20m long narrow channel were mitigated by including a walkway to the side of the Larinier channel, which will allow the client to safely access and maintain the pass.

To limit the public interaction with the pass, it was agreed with the Environment Agency that the pass would be closed in the summer months, outside of the key upstream or downstream Brown Trout migration seasons.

Environmental risks were mitigated by early and prolonged engagement and the development of an Environmental Management Plan during the design phase. This provided a clear plan for the management of environmental issues across the whole lifecycle of the project.

Want to know more?

The formal opening of the Langsett fish pass is taking place today, Friday 20 April, where Dave Mould will be representing JBA. Email Dave Mould for more information on this project or visit our fisheries web page for more information on how we can help you with your projects.

Are you attending the River Restoration Conference on 24-25 April? We’ll be showing you how our catchment and river restoration team deliver innovative and sustainable solutions to improve our rivers and catchments.

We are giving four presentations and have eight posters for you to see our project examples. Read the abstracts to find out more in our interactive guide below.

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