Fish passage improvement measures with Natural Resources Wales

We designed eel passage improvement measures at 11 gauging stations across North Wales. Our collaborative approach facilitated the integration of all client team requirements into our design work. Natural Resources Wales (NRW) have so far installed our designed solutions at four of the sites and a further six sites are programmed to be installed.


The gauging infrastructure at the sites ranged from low head crump weirs to compound crump weirs with existing multi-species fish passage measures already installed.

Whilst minimising impacts on the hydrometric functioning and accuracy of the gauging weirs was a key design criterion at all sites, some locations required pumped solutions, as gauge sensitivity and structure meant the existing weirs could not be broken into.


The design criteria defined by each of the client teams meant that this was a truly collaborative project. Our civil, structural and mechanical, and electrical engineers were able to work alongside fish ecologists to undertake extensive consultation. This was facilitated through collaborative design workshops and teleconferences involving hydrometry and telemetry, fisheries and project delivery teams.

As part of the range of gravity solutions provided, we made use of eel tiles and mussel rope climbing substrate at seven of the sites. Whilst at three others we proposed pumped solutions. To assist the client team in understanding the flow of water required to deliver a target depth of water on an eel tile with a lateral slope, we undertook Computational Fluid Dynamics (CFD) modelling.


The delivered solutions provided confidence in technical performance, and in a way that could be safely and easily maintained. NRW have so far installed our designed solutions at four of the sites and a further six sites are programmed to be installed.

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Want to know more?

For more information on this project please contact Jon Whitmore. Find out more about our Environment and Sustainability work here.


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