Fish Passes & River Structures
www.managingwater.co.uk
Improving morphology and fish passage in high energy rivers
By Jenny Mant and Victoria West (the River Restoration Centre, UK)
The EU RESTORE partnership (
www.restorerivers.eu) is funded by the EULife+ information and communications programme. As part of the RESTORE project the partners are required to organise workshops based on specific topics of interest and priority.
areas of possible sediment deposition within the river system, and could help to facilitate the production of policies that promoted river connectivity techniques for fish passage and natural river processes.
This event focused on the impact of barriers (to sediment, flow and fish) on high energy river systems, and the benefits of implementing natural fish passage, including discussion about what barriers fish can really pass. It aimed to discuss current best practice for fish passage, and identify how the EU RESTORE partnership can disseminate this information to policy makers, river basin manager and other key stakeholders in Europe. The one day event, followed by a site visit, was attended by around seventy delegates included presentations on hydropower needs and fish passage, the development of tools for the assessment of passability of riverine obstacles for fish, and to support the cost effective implementation of restoration measures.
Some of the key findings were as follows:
Sediment release when removing obstacles to fish passage was seen as the key concern, together with the risk of contaminated sediment release. A case study presented by Scottish Natural Heritage highlighted the issues of barrier removal for freshwater pearl mussels, which have been identified as a threatened species by the IUCN (International Union for Conservation of Nature and Natural Resources) Red list. Removal of barriers has the advantage of re-connecting sediment transport mechanisms to ensure sediment replenishment of important mussel habitats. However, it may also threaten these habitats due to sediment release which can smother juveniles and other essential habitats such as coarse sand and gravels. Delegates highlighted that there was a lack of confidence in dealing with possible issues of sediment release, stating a need for further research and monitoring programmes in this area. REFORM (REstoring rivers FOR effective catchment Management) was identified as a project that is aiming to develop protocols and procedures that will help address this. RESTORE plans to work closely with this project in the future to ensure that lessons learnt are transferred and incorporated into these initiatives.
More extensive river systems were acknowledged as more complex hence potentially increasing the risk and uncertainty associated in applying restoration principles.
Weir removal in high energy environments in particular was identified as difficult. The impacts both up and downstream of the proposed removal are often seen as unknowns. More guidance was called for and the idea of a handbook was discussed. This, it was suggested, could help reduce the risk associated with barrier removal by identifying
Hydropower plants and dams have been identified by the WFD as one of the top hydro- morphological pressures in Europe due to their restrictions on flow and sediment regime. Mitigation measures and ecological compensation should therefore be a requirement for any hydropower schemes in all countries in order to meet good ecological status for the WFD. Natural bypass channels, it was suggested, should be designed beyond the requirement of fish passage, allowing for morphological and ecological connectivity. During the workshop a requirement was highlighted for additional research into fish biology, and associated design criteria for specific species which is appropriate to the needs of practitioners. A need was identified for structures to mimic the slope, morphology and hydraulic conditions of the original stream and enable fish of different species to migrate, taking into account the different swimming capabilities of fish. EIFAC (European Inland Fisheries Advisory Commission) aim to define design criteria for fish passes in high energy rivers based on species, and produce best practice guidance on up and downstream fish. Once completed the RESTORE webpage will link to this guidance.
The role of stakeholders was also highlighted at the workshop. It was recognised that they have often been sceptical about the idea of restoring rivers especially in the context for flood risk. It is vital that the restoration community mitigate this by outlining the variety and significance of benefits that restoration can bring, and give details of the likely success of the proposed works. Demonstration sites would be useful, it was deemed, to illustrate “success stories” and the RESTORE River Wiki online resource for best practice river restoration projects across Europe will provide a useful and updateable resource (
http://riverwiki.restorerivers.eu/wiki/index.php? title=Main_Page).
Site visits to the Inchewan Burn a tributary of the River Tay, where a previously degraded river was restored to mimic natural process and improve fish passage, together with Pitlochry Dam and the River Tummel and Ballinluig all provided the participants a chance to discuss the challenges highlighted within the workshop.
The full details of this workshop will soon be posted on the RESTORE website and can be found alongside the other initiatives that have been the focus of this project across Europe. The website provides a wealth of information about all aspects of river restoration and we would always be interested to hear about your project, issue or concern. For further information contact the River Restoration Centre (
www.therrc.co.uk) who manage part of the RESTORE project and speak to one of the technical team.
www.fadsdirectory.com
Inchewan Burn below the A9 Before restoration (above) and after (below)
Sediment bar on the Inchewan Burn 19
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36