Spotlight on Nant Llwynog Scheme
Constant flooding and erosion had been causing some serious problems for Merthyr Tydfil Council who manage an old reclaimed tip site, close to the village of Bedlinog in the Taff Bargoed Valley.
Salix was brought in to do a full site analysis, design and implementation of a restoration scheme which would slow the flow of the Nant Llwynog, a concrete-lined channel that takes water from the mountains at high speed and in large volumes.
The company was also tasked with stopping the flooding and erosion of the public footpath alongside the stream, whilst improving the habitat.
Salix proposed holding more of the water up at the top end of the park by desilting two of the ponds and by creating three new ponds linked to the main channel to attenuate floodwater. Salix also recommended reshaping the stone-lined channel to create a grass and reed-lined swale.
A channel through the middle of the large top pond was desilted and its exit to the swale was raised to increase attenuation capacity. Installing Rock Rolls and seeded soils in the stream bed, protected with ananti-erosion turf reinforcement mat, increased capacity at the top of the park. A new area of wet woodland was planted next to the new attenuation pond to further enhance biodiversity and reduce runoff.
To preserve the footpath, the second existing pond was also dredged and a new pipe installed to take excess water beneath the footpath to a new attenuating pond.