New bridge will help boost fish numbers and reduce flood risk
7 November 2024
Working together, officers from Powys County Council and the Natural Resources Wales' (NRW) Four Rivers for LIFE project have replaced the crumbling original 1950s pipe bridge near Heol Senni, South Powys, with a new clear-span steel bridge.
The old bridge was supported by a series of concrete pipes on the riverbed which regularly got blocked. This restricted the passage of migrating fish, reduced the quality of the river's biodiversity and increased the river's flood risk.
Installed earlier this year by A.V Plant Ltd, the new bridge has been designed to allow the important process of gravel movement along the riverbed, thus restoring the river's habitat and creating a more natural environment for fish and invertebrates to feed and breed successfully.
The River Senni is part of the River Usk SAC (Special Area of Conservation) and an important spawning tributary for Atlantic salmon. However, access issues have led to decreased salmon spawning opportunities in the headwaters of the river. Recent declines in salmon numbers across the catchment mean that when the adults reach these tributaries, they must have open access to clean water and gravels in which to spawn, and for their young to thrive. As a result of the installation of the clear-span bridge, approximately three kilometres of upstream river will now be fully accessible to breeding salmon, trout and other important species.
'Green engineering' has also been used to stabilise the riverbank upstream of the bridge. Tree roots have been installed into the bank to protect the bridge and reduce erosion. Trunks four to five metres in length and 50-60cm in diameter have been laid horizontally and further held with two-metre-long chestnut stakes. Coir matting has been placed on the top of the trunks and seeded with native vegetation, which will further control erosion and help to stabilise the riverbank in the long term.
Cllr Jackie Charlton, Cabinet Member for a Greener Powys said: "Working together with NRW on this project has been great. We have been able to discuss different elements throughout the feasibility and design stage and develop and deliver a solution which meets the needs of everyone efficiently.
"As well as helping the environment and biodiversity of the river and surrounding land, the local community will also benefit from the new bridge which will reduce the frequency that the road floods and is subsequently closed. The new clear-span structure will result in lower maintenance costs due to no longer having to periodically clear the blocked pipes of the original bridge."
Susie Kinghan, Four Rivers for LIFE Project Manager said: "Fish make up a huge part of Wales's biodiversity and improving their habitat and ensuring populations are sustainable is a vital part of our work. Already this summer, we have found good numbers of juvenile salmon upstream of the new bridge, which is very positive news.
"We are working with partners like Powys County Council to identify similar barriers to fish migration and will use this scheme to show how low-cost solutions like this can work with nature and benefit people at the same time."
Watch a NRW time-lapse video of the work on this link: Pedair Afon LIFE a Chyngor Sir Powys / Four Rivers for LIFE and Powys County Council
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