Stage 2 Fish Passage : Concept Designs, Solutions and Appraisal
Based on the outcomes of Stage 1 and appropriate fish passage and geomorphology guidelines, a long list of proposed fish passage (and habitat) solutions was derived. The most viable fish passage short listed solutions identified were appraised through a detailed engineering and environmental assessment against key environmental receptors including fish passage, hydrology, geomorphology, environment (e.g., ecology, heritage, and recreation), WFD compliance, condition, and practicality. Potential habitat restoration solutions were also identified which would complement the solutions.
The appraisal took into consideration a tested philosophy that has been implemented by Royal HaskoningDHV on catchment-scale fish passage appraisal projects throughout the UK, as outlined below:
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potential to remove any barriers to fish passage entirely will be considered and recommended unless there is clear evidence that this is not feasible.
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If the constraints associated with individual structures are likely to preclude complete removal, the potential to modify the structure to improve fish passage and reduce impoundment will then be considered.
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For any structures that are operable or contain operable components, we will also consider changing the way they are operated if removal or modification is not feasible.
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If modification is unlikely to be feasible, the potential to install a bypass channel designed to reproduce naturally occurring features and flows suitable for the species of concern will be assessed.
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If there is no realistic potential to locate a bypass channel, then a technical fish pass or rock ramp installed onto the existing structure will be considered, or modification of structures will be recommended.