The RAB Team are always excited to visit new initiatives designed to improve river and coastal assets, and recently Rob Pike (Senior Advisor) and Charlie Davies (Apprentice Civil Engineer) went to see an ambitious river restoration project on the River Tarell in Brecon, Wales.
Background
At Ty Mawr Farm, the Four Rivers For LIFE Project has worked collaboratively with Natural Resources Wales, and the National Trust (as the landowner), to implement a unique and innovative Nature-based Solutions (NbS) scheme to re-connect the floodplain and improve in-channel habitats.
The projects core objectives were to:
- Re-connect the channel to its floodplain.
- Slow the flow to enable the channel to spill into the floodplain during periods of high flow, helping to reduce flood risk to communities downstream.
- Improve in-channel and riparian habitats.
Given the rural location in the upper catchment, and buy-in from the National Trust, there was an opportunity to focus on implementing NbS rather than hard engineering options. The main intervention comprised depositing large wood across the channel by simply felling existing trees along the river banks. Machinery was used to pull the trees across the channel in one piece. In many cases the trees are still alive and continue to grow in their new horizontal position. Since the works were completed, silt and branches have now built up in the channel bed, creating natural dams along the channel.
Initial consideration was given to ensuring that de-rooted trees did not destroy wildlife habitats. During the selection of which trees to de-root, all trees were investigated to ensure that no selected trees had any present wildlife habitats.
Further upstream, the high ground and informal embankments have been cut into and lowered to create routes for water to escape into the floodplain during periods of high flow.
Benefits and Limitations
- The trees have caused the build-up of silt and vegetation as intended, slowing the flow and increasing the channel bed height.
- Positive impact on the adjacent wetland by allowing water to escape onto the floodplain more readily.
- Improved in-channel and riparian habitats. There was clear evidence of increased deposition within the channel, creating areas of lower flow to support a variety of existing and new wildlife.
- Reduced flood risk to downstream communities, with negligible adverse impacts to the areas encouraged to flood given the rural upland location and agricultural use.
Key Learning Points
The key learning point was seeing how simple and innovative solutions can reduce flood risk, whilst simultaneously altering the hydrogeomorphology to benefit the river’s habitat. The common goals and collaborative working of all the project partners was clear to see, and meant there were relatively few hurdles to overcome in successfully delivering the project. The Project is now looking to explore further interventions along additional reaches of the River Tarrell downstream.
RAB deliver a wide range of asset management, public safety and engineering services for both public and private sector organisations. More information is available here on our website, or you can get in touch for an informal discussion on your specific project by email to enquiries@rabconsultants.co.uk or call our head office in Lichfield on 0330 223 6475.