Improving Our Rivers

From Concept to Design

Removing barriers to fish brings a significant benefit to the biodiversity and overall health of our rivers. On the steep and fast-flowing rivers in the UK, where there are a large number of historic structures designing fish passes that are both in sympathy with the existing structures and effective for fish can be very challenging.

Edenvale Young Associates bring detailed hydraulic modelling to the process that can demonstrate how a proposed design will perform at the earliest stages of a project. We can offer a complete service from hydraulic modelling and conceptual design of fish passage structures through to detailed design, ensuring that changes to the concept at detailed design stage see the same level of analysis and do not compromise the effectiveness of the fish pass.

Holistic Analysis

How we Approach Fish Passage

We offer a complete service from initial concept to design drawings for construction. We:

  • Use the latest UK guidance from the Institute of Fisheries Management to inform our design choices and maximise the likelihood of approval
  • Perform a site-specific low flow analysis to ensure that we properly understand the design flows
  • Undertake detailed hydraulic modelling of the proposal, including the watercourses upstream and downstream to ensure that the flow velocities and forces within the fish pass meet the design criteria
  • Prepare outline designs to support permitting
  • Support the tender process to find a suitable contractor
  • Produce complete, detailed design drawings suitable for construction

The importance of Hydraulic Modelling


Fish passes can be designed using empirical methods and guidance outlined in the Fish Pass Manual from the Institute of Fisheries Management, but we have frequently found that there is a need for more detailed analysis. Oftentimes in the UK, rivers are not straightforward linear features flowing from upstream to downstream but have a series of bifurcations and confluences as they split into historic channels and leats. Detailed hydraulic modelling can resolve these flow splits and demonstrate how the proposed siting of a fish pass will change its effectiveness, revealing potential issues with depth of water or attraction at an early stage of the design process.

Monitoring the health of fish in rivers Monitoring the health of eels in rivers


Design and Construction

Fish passes must provide a low velocity / controlled depth environment to allow fish migration but they must also be designed for high flows to ensure that the structure is geotechnically, hydraulically and structurally stable but does not increase flood risk and is sustainable in the long term. Our experience encompasses: pool and riffle, baffled passes, rock ramp passes, bypass channels, Larinier and Alaskan fish passes.

Edenvale Young values close co-operation with the client during the concept design stages but we also recognise that our hydraulic modellers and civil engineers must work closely to produce efficient and economic designs. Our engineers and hydraulic modellers are trained to an appropriate level in hydrology and hydraulic modelling to ensure that both disciplines understand how to apply the constraints and principles contained in the Fish Pass Manual to ensure that the modelling and civil design are closely aligned.

We promote a design approach which uses a common 3d model which can be used within the hydraulic modelling environment and for the production of design drawings. Our design services include the preparation of drawings (CivilCad3D), specifications and contract documentation (NEC) for tender and construction. We also have experience of working in a design and build environment and are able to support our clients during construction.

If you need a hydraulic model or want to discuss how hydraulic modelling could be used to benefit your proposed development or scheme, contact us to discuss your requirements.

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Registered Address: 30 Queen Charlotte Street, Bristol BS1 4HJ, UK